Haulage Gavaud

Olivier ; Brehier

Odile ; Guilbault
email: guilbault@inrets.fr

Michèle ; Niérat

In Olivier French

Gavaud

Odile Brehier

INRETS. Michèle ; Guilbault

Patrick Niérat
email: patrick.nierat@inrets.fr

Olivier ; Gavaud
email: olivier.gavaud@developpement-durable.gouv.fr

Odile ; Brehier

Organization and subcontracting relationships in French road

Keywords: road haulage, subcontracting, partnership

Today road haulage is France's most important transport mode, proving its ability to meet shippers' demands. Road haulage has several success factors, some of which are technical (for example, the speed and density of the motorway and road network). Others are economic (the low price or road transport). Last but not least, relationships among road hauliers play a major role in competitiveness. Among other factors, the opportunity that large companies have to subcontract with very small ones, with very low fixed costs and great flexibility, is often quoted as a major advantage.

The ECHO survey, conducted in France in 2004, provides information on 10 000 shipments made by 3000 shippers. For each shipment, the survey gives details about the shipper, the

INTRODUCTION.

As in many other European countries today, road haulage is France's main transport mode, demonstrating its ability to meet shippers' demands. The success factors are numerous: some of them are technical (for example, the permitted speed and the density of the road and motorway network), others are economic (the low price of transport). Last but not least, relationships among road hauliers play a major role in competitiveness. Among other factors, the opportunity that large companies have to subcontract with very small ones with very low fixed costs and great flexibility is often quoted as a major advantage. This paper's aim is to explain the various road haulage organizations and focuses on subcontracting.

The survey of French shippers (named "ECHO") provides an opportunity to study how "physical" characteristics of each shipment (weight, distance, value per weight unit) impact the organization, and the role of big and small carriers in this organization.

The ECHO survey, conducted in France in 2004, provides information about 10 000 shipments forwarded by 3 000 shippers. For each shipment, the survey gives details about the shipper, the shipment itself, and the companies providing transport or logistics services.

The first section is a quick summary of road haulage evolution since the eighties in France. Section 2 presents the ECHO database. The third section introduces the different kinds of organizations in road transport (in terms of numbers of carriers). Sections 4 and 5 show the strong link between two particular organizations, own account and integrators, and the physical Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. characteristics of shipments they deal with. Section 6 focuses on the relationship between shippers and carriers. Section 7 studies the relationships between carriers. Here, the different kinds of subcontracting, and what they reveal about how carriers seek competitiveness, will be explained.

THE EVOLUTION OF ROAD HAULAGE IN FRANCE.

During the eighties and nineties, except for agricultural products, flows of raw products tended to decrease, whereas manufactured goods increased. These trends are the consequences of new industry phenomena [START_REF] Salini | La part des choses. Histoire, géographie des flux, règlementation, économie[END_REF] :

low labor costs in emerging countries justify the importations of manufactured instead of raw goods, -concentration on the core business and specialisation of production units have meant potential productivity gains, -the decrease in the average shipping weight allows a decrease in stocks.

The latter has been shown by Guilbault and Houée (to be published) and is of paramount importance to the transport industry.

This new way of organizing industrial production is made possible by strong improvements in supply chain management. Supply chain management is then defined as the link between scattered product units. [START_REF] Savy | Le transport de marchandises[END_REF]. A striking effect is the rising use of road transport since the mid-eighties, since road transport is well adapted to small shipments. Thus, as in many European countries, road haulage has increased to become, by far, France's primary transportation mode : In 2008, 87 % of tonne kilometres in France moved by road [START_REF] Cgdd | ème rapport à la Commission des comptes des transports de la Nation[END_REF].

Besides, road hauliers face an incessant pressure from customers to reduce costs while maintaining and improving effectiveness [START_REF] Davies | Assessing the impact of ICT on UK general haulage companies[END_REF].

On the one hand, in order to adapt to the evolving market, the road hauliers sector has tended to become more concentrated since the mid-eighties. On the other hand, the number of small road haulage companies has increased dramatically. [START_REF] Salini | La part des choses. Histoire, géographie des flux, règlementation, économie[END_REF]. At the same time, road haulage prices have decreased, and margins subsequently have decreased since the beginning of the nineties. [START_REF] Bernadet | Le transport routier de marchandise. Fonctionnement et dysfonctionnements[END_REF].

This situation is often explained by the share between big and small road hauliers : big ones are supposed to be able to sell a whole service to shippers, subcontracting the only road haulage, whose margins are low, to small hauliers. [START_REF] Cussy | La sous-traitance dans le secteur du transport routier de marchandises[END_REF]. In the Netherlands, road haulage is characterised by many family enterprises, with 81 % owning fewer than 10 vehicles. Small enterprises often fail and are used by larger firms for subcontracting [START_REF] Karis | Impact of te road transport directive : a survey of road hauliers in the Netherlands[END_REF].

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. The reality is not so straightforward : A. [START_REF] Sauvant | Transport routier de marchandises[END_REF] emphasizes that subcontracting rates of big French companies for intercity road haulage are only about 15 % of their total sales. M. [START_REF] Savy | Le transport de marchandises[END_REF] explains that big and small companies need each other, and have a much more complex relationship than that described above. [START_REF] Carbone | Growth and relational strategies used by the European logistics service providers : Rationale and outcomes[END_REF], studying European logistics service providers, most of whom are also road hauliers, quote three prime objectives that led 3 PLs to link. These are as follows :

to enlarge and strengthen the geographical network concerning a specific business, -to penetrate new markets, in terms of services, -to penetrate new geographic markets, dominantly beyond Europe.

This paper aims to use figures to describe and quantify the relationships between road hauliers.

THE "ECHO" SURVEY.

The ECHO survey was conducted in France in 2004 [START_REF] Guilbault | Demand for transport and production systems -Shipper surveys in France in 1988 and[END_REF]. The aim of this survey was to provide a comprehensive description of transport chains based on the door-to-door tracking of each shipment, from the shipper to the final consignee. Shippers were also interviewed about their production constraints and transport practices. This information allows us to analyze the link between production and transport. The survey also allows us to study subcontracting between carriers, as the tracking of shipments includes trips and carriers involved.

"Shipment" is defined as a quantity of freight that is made available, at a given time, in order to be transported during a single transport operation from a given shipper to a given consignee. It is the natural observation unit for reconstructing transport chains. The shipment is a representation of transport closely integrated with the production and distribution process. It allows us to understand the economic context of the exchange of goods.

The ECHO survey was based on the observation of 2 935 shippers and 10 462 shipments, of which 24 % were international, and 9 742 transport chains.

The survey covered sites with 10 or more employees in the wholesale trading and industrial sectors, not including mining, building and construction. It also covered mail-order companies, farm cooperatives, warehousing services and industrial waste treatment centres. The total of about 70 000 sites surveyed covers all of metropolitan France; the average sampling rate was 4 %. These characteristics of the survey scope affected the portrayal of the total traffic measured in that they excluded almost all large bulk shipments of raw intermediate goods (raw oil products, solid mineral fuels, ores and minerals, raw construction materials such as sand and gravel). Nevertheless, a large range of sectors was covered, in particular those undergoing the most rapid change. In terms of national transported tonnages (national shipments and the part of export transport which occurs within French territory), in 2004 this scope represented approximately 47 % of total tonnage. When the large bulk shipments mentioned above are excluded, this scope accounted for 84 % of total tonnage.

Another characteristic of the survey scope relates to the choice of shipments that were surveyed. It was decided to consider all freight shipments with no limit other than a minimum weight of 1 kg. The selection of this very low threshold enables us to highlight the very large number of small shipments which are an important aspect of the modern economy. The frequency and size of shipments are closely linked, so the representation of heavy shipment was increased.

Interviewing some integrators (Fedex, UPS, DHL, TNT, Exapaq, Chronopost, La Poste) was not possible. The integrators' websites listed the trips by origin and destination of the shipments, but the different carriers involved in each shipment are not known.

OVERVIEW OF DIFFERENT TYPES OF ORGANIZATIONS.

In this section, for every defined market segment, the shares of different types of transport organizations are given, especially those which involve subcontracting.

The freight transportation market is not homogeneous. We use the following shipping weight categories to define the different market segments :

-Up to 30 kg : single parcel delivery service -Between 30 kg and 300 kg: parcel delivery service -Between 300 kg and 3 t (metric tonne) : less than truck load (LTL) -Between 3t and 30 t (in fact 25 t): full truck load (FTL).

These market segments are not only a matter of trade : these different weight categories use different networks (storage facilities and haulage lines).

The choice of these categories can be discussed and criticized, but results for each market segment are more relevant than results aggregating the market segments, as each market segment is a very different situation.

In order to focus on subcontracting, the type of organization is defined by the number of carriers involved in the shipment forwarding:

own account transport : the shipment is carried by the shipper, -one carrier : only one carrier transports and provides logistic services for the shipment; -several carriers, without subcontracting : several carriers transport and/or provide logistic services for the shipment, each of them contracting directly with the shipper.

two carriers : one carrier contracts with the shipper, and subcontracts partly or totally to another carrier; -more than two carriers : one carrier contracts with the shipper, and subcontracts partly or totally to more than one carrier;

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick.

integrators : as explained in the previous section, integrators correspond to several companies (Fedex, UPS, DHL, TNT, Exapaq, Chronopost, La Poste) which were not possible to interview. Integrators are then excluded from the final stages of the analysis, as explained in part 6.

Figure 1 shows that "own account transport" and "one carrier", without any subcontracting, are the two main types of organizations, carrying 65 % (31 % "Own account transport", 34 % "One carrier") of shipments (for all weights of shipments). This share increases with the shipment's weight, from 54 % for shipments under 30 kg, to 84 % for shipments heavier than 3 t. Other kinds of organizations deal with less than 15 % of shipments, except integrators which deal with 31 % of light shipments under 30 kg. Two weight values act as thresholds :

below 30 kg, integrators take a large share of shipments (30 %) -above 30 kg, the "one carrier" organization becomes important (around 40 % of shipments) -above 300 kg, own account increases to reach 40 % of shipments.

The following sections show the link between "physical" characteristics of the considered shipment (weight, distance, value per weight unit) and the transport organization. Two types of Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. organizations show a strong link with physical characteristics of the shipment : own account transport, and integrators.

OWN ACCOUNT TRANSPORT.

Own account transport (OAT) is the organization used for 31 % of shipments and 30 % in tonnes, in the "ECHO" field, described in section 2.

Figure 2 gives distributions of shipping weight, distance and value per tonne for each type of organization. For instance, the first graph gives the distribution of shipping weights : for a given shipping weight, a curve gives, for the considered organization, the share of shipments below or equal to this weight, out of the total number of shipments.

It appears that shipping weights carried by OAT are similar to those forwarded by other types of organizations; but distance and value per weight unit are remarkably lower. In more than 70 % of cases, shipments forwarded by OAT are part of a round trip. A round trip is a trip beginning and ending at the same place, allowing the delivery of goods to several clients.

Unfortunately, ECHO was not designed to accommodate OAT. The ECHO survey does not give detail about the inner organization of OAT, so the analysis cannot go further.

INTEGRATORS.

Integrators are chosen for 17 % of shipments and 1.5 % of tonnes, for the "ECHO" field.

Figure 2 shows that integrators are chosen for shipments of low weight and rather high value per Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. tonne. This is consistent with the use of "just in time" transport for goods which can't be stocked in big amounts, considering their value.

Integrators were not possible to interview. Thus, their own subcontracting can't be analysed, although these kinds of carriers are known for their subcontracting.

In this first section, we saw that OAT and integrators forward very particular shipments in terms of weight, distance and value per weight unit. The ECHO survey doesn't enable further investigations for these organizations. We also saw that other types of organization (one carrier, two carriers, more than two carriers) cannot be distinguished by analysing Figure 2. Further investigations must be undertaken to explain why these types of organizations were chosen. In the following sections we analyse each stage of the organization : the relationship between shipper and carrier, and between carriers.

RELATIONSHIP BETWEEN SHIPPER AND CARRIER.

OAT and integrators are now excluded from the analysis. Thus we are now analyzing 52 % of the shipments, and 68.5 % of the tonnes.

Two features are used to characterize the carriers : the number of employees, and the relative position of the two carriers working in partnership. The nature of service provided by the carrier being analyzed is also examined.

First of all, we focus on the nature of service the shipper entrusts the carrier with, then on the contract between the shipper and the carrier.

6.1. Kind of service provided by carrier to shipper.

Categories used for the analysis.

The "ECHO" database gives details about the services provided by the transport carrier using the following categories :

material operation directly linked to transport : this refers to a material operation such as change of vehicle, providing a container, or loading/unloading a container… -tracing : this refers to tracing by information technology.

freight forwarding with a trip : the carrier carries out part or all of the freight forwarding, and at least a part of the transport, -freight forwarding without a trip : the carrier carries out part or all of the freight forwarding, but not the transport : the transport is subcontracted to another carrier. -formalities : formalities such as quality control, customs formalities, -stocks management and picking, -post-manufacturing, -warehousing, customs transit in ports or airports, handling.

In order to simplify the analysis, three groups of services are used, which are representative of the levels of service :

the low service level is for shipments requiring no other service except transport, or only "material operations directly linked to transport", -the intermediate service level is for shipments requiring value-added services related to transport : these shipments do or do not require "material operations directly linked to transport" and either one or both of the following services : "freight forwarding with a trip", or "tracing" (using information technology) . We stress that this kinds of services are the ones required for consolidation and deconsolidation.

-The high service level is the previous level with one or both of the following services :

"stock management and picking", and "formalities". These services go beyond simple transport, or else they deal with international transport, which requires specific knowledge.

Other cases are services combinations which don't fit into our three "service levels". This can be an isolated service such as only "warehousing" only.

Share of each service level.

We count the share of each service level by building a tree, each branch of the tree representing "yes" or "no" for the fulfilment of a service. We start by the most frequent service (material operations), then for the second most frequent (tracing) and so on. Table 1 gives the results of this classification. 38 % of shipments require a high level of services. For each market segment, this share is bigger than 24 %, and is particularly big for shipments between 30 kg and 300 kg. A further analysis shows that only 5 % of shipments below 30 kg require stock management and picking.

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. This can partly explain the relatively low rate of high level services provided to these shipments.

33 % of shipments require an intermediate level of services. This level, which reveals the consolidation and deconsolidation operations, is required for nearly one out of two shipments for those shipments below 30 kg, but only for 17 % of heavy shipments. Integrators and OAT are not included in the analysis, but these organizations often provide high and intermediate levels of shipping service.

A low level of services is provided for only 13 % of total shipments. This share is strongly related to shipping weight : for heavy shipments, this low service level is provided one out of every three times, whereas for small shipments, it is provided only 8 % of the time. This explains why 29 % of the tonnes in the ECHO field fall into the "low" service level category.

Table 1 shows that a large part of the services provided to shipments is directly linked to the consolidation and deconsolidation requirements : these are present in the intermediate and high service levels, which account for 71 % of shipments, and 53 % of tonnes.

Shipments above 3 tonnes (33 % of shipments) often require a low level of services, but quite often too, a high level of services, and combinations of services which don't fit into our three "service levels". Transport for this weight category can't be reduced to road haulage only : the variety of situations is great, as some shipments of this weight require consolidation, some don't, and some require other kinds of services.

Transport agreement between shipper and carrier.

The first question about transport organization is to know who decides it. In the ECHO field, the first carrier is nearly always (95 % of cases) chosen by the shipper. The consignee chooses the first carrier in only 5 % of cases. This underlines the important role of shippers in transport organization.

To what extent do shippers contract with large versus small carriers ? Table 2 OAT and integrators excluded.

In general, the lower the shipping weight, the larger the market share belonging to large carriers. The exception is for shipments below 30 kg, where small companies are relatively frequent, making up 26 % of shipments. This is due to carriers who transport short distances : two thirds of the shipments carried by these small companies are carried less than 50 kilometres.

This observation can be explained by the requirements of consolidation for small shipments :

a network of consolidation facilities, with accompanying staff, to cover a large territory, -a high number of shipments in order to make them profitable, -efficient information systems, to monitor the high number of shipments.

Big companies more easily meet these requirements than small ones, and are able to build such a service with a high number of employees and large assets. These requirements tend to decrease when the shipping weight rises : they are weaker for LTL than for parcel delivery service, and tend to vanish for FTL shipments when no consolidation is needed. In this last case, big companies as well as small ones are able to fulfil shipper's requirements.

Before detailing subcontracting between carriers, the following features of shipments forwarded by only one carrier have to be stressed.

Shipments forwarded by only one carrier are heavier than the average, and are heavier than the average weight of shipments forwarded by carriers who subcontract a part of the transport (namely 1.8 tonnes,1.3 tonnes and 0.6 tonne). As shown in Table 3, they are more often forwarded by small carriers, even if big companies are the most frequent. We have shown that shipping weight, and then the consolidation operations, determine a large part of the services provided for the shipment; and also strongly determine the carrier size.

This section examined the contract between the shipper and the carrier. The next section examines the contract between carriers, when some services are subcontracted by the first carrier.

SUBCONTRACTING BETWEEN CARRIERS.

OAT and integrators are still excluded from the analysis. Shipments without any subcontracting are also excluded. As the aim is to explain relationships between road hauliers, shipments commissioned by the shipper to forwarding agents are also excluded. The following analysis therefore concerns 14 % of shipments (see Figure 1), and 7 % of tonnes of the total ECHO field.

Six different kinds of subcontracting.

Six different kinds of subcontracting are distinguished. This is based on how the carriers define their role for the shipment in question (forwarder, road haulier, non-road carrier) and on whether or not the carrier and subcontractor belong to the same conglomerate. These six kinds of subcontracting are detailed below :

road haulage subcontracting : a road haulier subcontracts to another haulier, not a member of the same conglomerate, -road haulage co-contracting : a road haulier subcontracts to another haulier, a member of the same conglomerate, -subcontracting as a purchase : the company which subcontracts is a forwarding agent or a railway, air or maritime carrier, -logistics subcontracting : the subcontractor does not do road haulage nor freight forwarding, -subcontracting to a forwarding agent, -subcontracting to a non-road carrier (railway, air, maritime).

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. In the first "consolidation network" subcontracting case (big carriers subcontracting to small ones, shipments below 3 tonnes):

the subcontractor provides a low level of service two times out of three (67 % of cases), -the big and small carriers' agencies involved in the subcontracting are usually (87 % of cases) located in the same region.

This case fits the "low product complexity/low asset specificity" outsourcing case described by [START_REF] Vining | A conceptual Framework for Understanding the Outsourcing Decision[END_REF]. According to them, this combination provides the clearest case for outsourcing.

In the second "consolidation network" subcontracting case (big carriers subcontracting to big ones, shipment below 3 tonnes) :

the subcontractor provides a high level of service in 52 % of cases, and an intermediate level of service in 31 % of cases, -the carriers' agencies involved in the subcontracting are usually located in different regions( 71 % of cases).

When the subcontracting reason, given by the carrier who subcontracts, is examined, strong differences are observed :

in the first case described above, "transport plan application", "search for low costs" and "lack of vehicle" are quoted more often than in the second case of subcontracting (41 %, 31 % and 17 % of cases, to compare to 8 %, 21% and 8 %), -in the second subcontracting case, "unusual freight or destination", and "outsourcing of drayage" are more often quoted than in the first subcontracting case (53 % and 34 % of cases compared with 15 % and 18 %).

Other reasons appear at a similar rate for both subcontracting cases.

For the FTL segment, subcontractors provide a low level of service two times out of three, but also a high level of service one time out of four.

Analysis of subcontracting reasons for each market segment shows particular features for FTL : the "unusual cargo or destination" is quoted in one subcontracting out of two, whereas "search for low costs" is rarely quoted. The two carrier agencies involved in co-contracting are mainly located in the same region (73 % of co-contracting).

Road haulage co-contracting

Co-contracting has then the same features as subcontracting between two big companies.

CONCLUSION.

Road hauliers interact through a wide range of organizations : there is no absolute organization rule, and there are many cases which run counter to the main trends we observe.

The ECHO database gives us a better knowledge of subcontracting. First of all, subcontracting between road hauliers is not that frequent, since ECHO database analysis (excluding "own account transport" and "integrators") show that subcontracting is present in only 14 % of shipments (7 % of shipments in tonnes).

The various analyses performed enable a better understanding of road haulage organization.

A major phenomenon has taken place these last twenty years : a decrease in the shipping weight. This has required consolidation and deconsolidation facilities, key elements of asset demanding networks. These requirements have made the advent of big carriers easier; these big carriers are commissioned by shippers in more than one case out of two for shipments lighter than 300 kg, and are still strongly present for shipments up to 3 tonnes.

For three road haulage segments, having in common the use of consolidation networks (single parcel delivery service, parcel delivery service, less than truck load) , it is mainly big companies that subcontract. Two main kinds of subcontracting can be distinguished :

-Large carrier subcontracting to a small carrier located in the same region, who provides a low service level. This kind of subcontracting is more often motivated by application of a transport plan, costs, and a lack of means such as lorries and drivers than is the other kind of subcontracting.

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. -Large carrier subcontracting to another large carrier, the offices of the carriers involved located in two separate regions, and the subcontractor providing a high service level. This kind of subcontracting is more often motivated by the subcontractors' network possibilities than is the other kind of subcontracting, even if low costs remains a necessary condition.

For the full truck load segment, which requires lower assets than other segments discussed above, large carriers are less frequently commissioned by shippers : shipments are forwarded, with similar shares (around 25 %), taken by large carriers (more than 500 employees) and by smaller carriers (100 to 499 employees, and 20 to 49 employees) (Table 2). Subcontracting is mainly conducted by a fairly large carrier (100 to 499 employees), whereas small carriers (20 to 49 employees) are more often subcontractors. All FTL subcontracting is chiefly motivated by the ability of the subcontractor to deal with an usual cargo or destination.

Beyond the search for low costs, subcontracting is also strongly motivated by the will to use the subcontractor's specialized skills. In transport, these are 1) a particular destination or region, 2) a particular cargo, or 3) a particular service combining destination, departure timetable, and transit time.

Comparisons of subcontracting habits from different countries would be interesting, but unfortunately databases similar to ECHO, with the same accuracy, do not exist in other countries to our knowledge.

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick.

Figure 1 .

 1 Figure 1. -For each market segment, share of different kinds of organizations, in % of shipments.

Figure 2 -

 2 Figure 2 -Distributions of shipments weight, distance and value for each kind of organization. Percentage of shipments

Table 1 -

 1 Level of services provided to shipments, for each market segment.

	Level of	Share of	Share of	Shipping weight
	services	total shipments "ECHO" field.	total weight "ECHO" field.	Below 30 kg, in shipments.	Between 30 and 300 kg, in shipments	Between 300 kg and 3 tonnes, in shipments	Between 3 and 30 tonnes, in shipments
	Low	13 %	29 %	8 %	11 %	18 %	33 %
	Intermediate 33 %	24 %	45 %	29 %	23 %	17 %
	High	38 %	29 %	28 %	44 %	38 %	24 %
	Other cases 16 %	18 %	19 %	16 %	22 %	26 %
	Total	100 %	100 %	100 %	100 %	100 %	100 %
					OAT and integrators excluded.

Table 2 -

 2 answers this question for each market segment. For each market segment, size of the carrier commissioned by the shipper.

		Organization and subcontracting relationships in French road haulage.
		Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick.
	Size of	Shipping weight.
	carrier in	% of shipments.
	number of	Below 30 kg Between 30	Between 300	Between 3 and 30	All weight categories
	employees	and 300 kg	kg and 3	tonnes	(% of tonnes)
				tonnes
	Below 20	26 %	6 %	9 %	11 %	15 %
						(11%)
	Between	5 %	6 %	8 %	23 %	7 %
	20 and 49					(22%)
	Between	7 %	3 %	9 %	13 %	7 %
	50 and 99					(13 %)
	Between	11 %	16 %	32 %	29 %	18 %
	100 and					(25 %)
	499
	More than	51 %	69 %	42 %	24 %	53 %
	500					(29 %)
	Total	100 %	100 %	100 %	100 %	100 % (100 %)

12

th WCTR, July 11-15, 2010 -Lisbon, Portugal 12

Table 3 -

 3 Share of shipments carried by large and small carriers (commissioned by the shipper) for two cases : the carrier doesn't subcontract, and the carrier subcontracts.

	Size of carrier	No subcontracting	Subcontracting
	Below 20 employees	18 %	6 %
	Other sizes	32 %	30 %
	More than 500 employees	50 %	64 %
	Total	100%	100 %

Table 7 -

 7 Co-contracting and subcontracting distribution in each market segment.

	Table 7 shows that co-contracting is mainly present for single parcel delivery service or parcel
	delivery service.

12

th WCTR, July 11-15, 2010 -Lisbon, Portugal 18

It's important to stress that the ECHO database gives information on the shipment, on the subcontractors and along the trips chain. When the shipment is subcontracted to another carrier, the latter can consolidate this shipment with others going in the same direction or to the same consignee. The shipment forwarded by the subcontractor is then heavier than the initial shipment. The Echo database gives information only about the initial shipment. For example, when a carrier consolidates LTL shipments on its consolidation facility and subcontracts the haulage, a 500 kg shipment can be consolidated with 10 tonnes of other shipments; in this case, the ECHO database would continue consider the 500 kg shipment.

What kind of subcontracting is the most frequent ? Table 4 answers this question, giving the share of shipments concerned by each kind of subcontracting. For "two carriers" organizations, total is below 100 % because characteristics of some carriers have not been quoted in the ECHO database. For "more than two carriers" organizations, the total is above 100 % because there are at least two, and often more than two subcontracts in these organizations.

Table 4 shows that road haulage subcontracting is the main kind of subcontracting : this kind of subcontracting occurs in 56% of "two carriers organizations", and 65 % of "more than two carriers organizations". "Co-contracting" is also frequent : it occurs in 37 % of "two carriers organizations", and in 41 % of "more than two carriers organizations".

Logistic subcontracting is scarce, showing that, in 2004, logistic services were mainly provided in association with transport.

Subcontracting to a forwarding agent occurs one time out of four in "more than two carriers" organizations, showing that forwarding agents are commissioned not only to deal with a whole shipment, but also as subcontractors, to provide a particular service.

The next section deals with road haulage subcontracting. For the two main kinds of subcontracting, we will focus on several features (size of carriers involved, services provided by the subcontractor, reason of subcontracting) to describe relationships between the carriers. The analysis of the Table 5 "Total" column and row leads to the following conclusions :

Road haulage subcontracting : size of carriers involved.

-Carriers who subcontract are mainly big companies : carriers of more than 500 employees represent 61.5 % of subcontracting between two carriers not belonging to the same conglomerate. This corroborates that few carriers subcontract (half of subcontracting, measured in amount of money, is done by less than 5 % of carriers) , and subcontracting use, in terms of turnover share, increases with carrier size [START_REF] Podevin | La sous-traitance transport dans l'enquête annuelle d'entreprise 1998. Notes de synthèse du SES[END_REF]) -Large carriers are often also subcontractors of smaller carriers. This shows that the case of large carriers subcontracting to smaller ones is not the only case by far, even if it is the most frequent. The relationship between big and small companies is more tricky than simple "master and servant". Lionnel [START_REF] Grand | L'équilibre de la sous-traitance en transport routier de marchandises en question :analyse au travers des théories des organisations[END_REF] explains that a carrier may subcontract to fulfil his client's needs, concentrating his own means on strategic or profitable tasks : in this system, every carrier may subcontract, or be a subcontractor.

A further analysis of Table 5 shows that the two main cases of subcontracting can be isolated. These two cases, "large carrier subcontracting to small one" and "large carrier subcontracting to another large carrier" each represent roughly 20 % of the total.

Analysing each market segment (single parcel delivery service, parcel delivery service, LTL) leads to the same conclusion.

Analysis of the FTL segment gives different results (178 records in the database) : carriers between 100 and 499 employees subcontract the most : 71 % of subcontracting is generated by these carriers. This is quite striking because carriers between 100 and 499 employees deal with only 29 % of shippers' needs for FTL transport (see Table 2). Subcontractors are often carriers

Organization and subcontracting relationships in French road haulage. Gavaud, Olivier ; Brehier, Odile ; Guilbault, Michèle ; Niérat, Patrick. with between 20 and 49 employees (64 % of FTL subcontracting cases). The ECHO sample for FTL is not big enough to say more.

In the following chapter, we are looking to characterize these different kinds of subcontracting.

7.3. Road haulage subcontracting : Consolidation networks and FTL.

Here, we call organizations dealing with shipments of up to 3 tonnes "consolidation networks", because using consolidation facilities, where consolidation is performed, is the most frequent way to deal with shipments of up to 3 tonnes.

FTL, dealing with shipments above 3 tonnes, generally uses other systems of organization.

Either a single shipment is big enough to fill the lorry, or the shipments are collected via a round trip, without using a consolidation facility.


C Eyssartier

F Hamelin

Acceptance of automated enforcement in France

Keywords: Traffic enforcement, automated devices, acceptance, policy analysis, France

The introduction in 2003 of automated checking and sanctioning of traffic offences brought a major change to road safety policy in France. What is required now is an appraisal of how it has been "accepted". The first part looks at the need to deconstruct the notion of social acceptance within the framework of an analysis of public policy and points up the interest of the focus group method in understanding this acceptance. The paper draws on recorded discussions by focus groups in the city of Nantes, in western France, in the second half of 2009 and the first half of 2010. The second part shows that the instrument in question is perceived as destabilising for the identity of the professionals in charge of its functioning. The road users questioned seem less bothered by the automated system, this being explained by greater practical adaptability on their part.

Introduction

The appearance of automated speed checking devices in France in 2003 brought about a major change in road safety policy, one most often examined in terms of its effectiveness [START_REF] Carnis | Automated Speed Enforcement: What the French Experience Can Teach Us[END_REF]. However we also need to know how this innovation has been received -"accepted" being the term we shall use here -by those it is intended for. Controversy has arisen in all the countries where this kind of system has been adopted [START_REF] Delaney | Controversies and Speed Cameras: Lessons learnt Internationally[END_REF], and in those places where automated enforcement was first used the main aspects of acceptability were quickly identified [START_REF] Streff | Field test of automated speed enforcement in Michigan: effects on speed and public opinion[END_REF]. In France the approach is all the more relevant in that use of automation was extended to red-light violations in 2009, prior to the introduction of automated reading of licence plates and computerised issuing of tickets. Research in this area has been carried out by INRETS [START_REF] Hamelin | L'Harmattan[END_REF] in the wake of work by state specialists [START_REF] Onisr | Impact du contrôle sanction automatisé sur la sécurité routière[END_REF]. The work presented here continues this initial research, but takes a fresh methodological slant [START_REF] Eyssartier | Acceptabilité sociale, professionnelle et politique de l'automatisation du contrôle des infractions au Code de la Route: enquête en Loire-Atlantique: données préparatoires[END_REF] The aim of this paper is to underscore the scientific interest of recourse to the notion of acceptance: firstly by presenting the input provided by the methodology -but without excluding the problems encounteredand secondly by indicating the results obtained from the population groups questioned.

] involving recourse to focus groups. We carried out four such investigations in late 2009 and early 2010, in Nantes, a medium-sized city in western France. They covered road maintenance and safety operatives, law enforcement personnel, representatives of organised civil society and road-using professionals (see Table 1). This research programme is being jointly carried out by teams from INRETS and CETE de l'Ouest.

Methods

Recourse to the notions of acceptability and acceptance is scientifically relevant in terms of assessing a new road safety policy instrument [START_REF] Hamelin | Renewal of Public Policy via Instrumental Innovation. The Implementation of an Automated Speed Enforcement System in France[END_REF] The notions of acceptability and acceptance can be defined very easily. Acceptability has to do with an individual's attitudes and reactions towards the system or device under study without having any actual experience of it; while acceptance, on the contrary, has to do with reactions and attitudes regarding something he has experienced. In the context of this research the first notion applies to automated redlight checks, which were not yet in operation at the time the study was undertaken, and the second to automated speed checking as implemented since 2003. ], as long as the notions of "social acceptability/acceptance" are deconstructed and there is recognition of the strong points and limitations of the methods used for pinpointing them. The method adopted here is that of focus groups.

2010 Australasian Road Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory 2

The French political scientists who make use of these notions see them as the result or the product of a political and/or administrative process of legitimation of action by the authorities [START_REF] Hamelin | Les dimensions politiques de l'acceptabilité du contrôle automatisé de la vitesse[END_REF]. The notions then characterise the narrow limits within which the government can apply its measures with the likelihood of being obeyed [START_REF] Tyler | Why People Obey the Law[END_REF]. Research undertaken in this area is then perceived as intended to identify these limits and even to hypothesise about measures conducive to acceptance by certain user groups and by public opinion in the broader sense [START_REF] Delaney | The History and Development of Speed Camera Use[END_REF]. In response to our colleagues' mistrust of research into acceptance of change in public sector action, our approach initially consisted in establishing the preconditions for scientific use of these notions in analysis of public policy. In addition to the adoption of a rigorous investigative methodology, this solution also involved deconstructing the notions of social acceptability and acceptance, as can be seen in various English-language contributions to the literature [START_REF]Acceptability of Transport Pricing Strategies[END_REF].

Most research to date focuses on acceptance and acceptability in terms of the groups the policies are aimed at: motorists, citizens, inhabitants and so on -the mass of the population in other words. In this context acceptance and acceptability are the product of a specific instrument, the opinion poll, i.e. a quantitative measure of the reception given the new measure by a predefined public, as expressed in its answers to a questionnaire. The outcome is known as "public acceptance". However, while pertinent in that it allows for distinctions between groups according to age, sex and other variables, this approach is not adequate for analysis of public policy.

Development of an effective programme of action also requires motivating and involving both the actors in charge of such development and those at whom it is aimed. In respect of the public road safety action under study here, then, it is essential to be able to grasp acceptance of the system by the local political authorities ("political acceptance"), the professional groups directly concerned ("professional acceptance") and various organised actors at local level. The notion of "community acceptance" [START_REF] Freedman | Public Opinion Regarding photo Radar[END_REF] incorporates this last-mentioned dimension, involving an aspect of physical and social togetherness in the sense that the community shares not only the same territory, but also a set of values and interests. We use the term here, although it does not necessarily fit with a specific reality in France; "community" should doubtless be replaced by "local civil society", especially since the research devoted to it involves questioning representatives of local associations that may be of a civic, religious or educational nature [START_REF] Wissinger | Using focus groups to investigate issues of red light running[END_REF] In the literature the professionals questioned are most often road police officers [ ].

14], sometimes operatives -engineers, technicians -from relevant administrative bodies and [START_REF] Fontaine | Feasibility of Real-Time Remote Speed Enforcement for Work Zones[END_REF], more rarely, members of the judiciary [START_REF] Cunningham | Evaluating the use of red light photographic enforcement using collisions and red light running violations[END_REF]. Gendarmes and traffic police are included in our study, especially since research into the implementation of automated enforcement has highlighted their core role [17 France ]. has two national law enforcement agencies with similar goals and attributions, including road safety policing, but someone different zones of activity. Today, large conurbations are handled entirely by the Police. Rural and suburban areas, and some smaller cities with populations ranging from 5,000 to 16,000, are handled by the Gendarmerie. We added a group of road infrastructure operatives: their attitudes have been little studied in automation research, even though their work is essential to the installation and upkeep of fixed devices and thus to the quest for long-term effectiveness. The local community, one of the groups addressed by English-language research, is spoken for by representatives of residents and road users' associations. The fourth group comprises people whose profession entails considerable drivingtradesmen, commercial travellers and taxi drivers covering over 100,000 kilometres annually -and who run a greater risk of sanctions than members of the other three groups. This focus group method had not previously been applied to the subject in France, whereas it had been used elsewhere: in, for example, the UK [START_REF] Wells | The Fast and the Furious: Notions of unfairness and injustice in criticisms of speed enforcement technologies[END_REF], the United States [START_REF] Fontaine | Feasibility of Real-Time Remote Speed Enforcement for Work Zones[END_REF] and Australia [20 Creation of the focus group is no easy matter; and the major problem once the group is rolling is achieving an equitable sharing of discussion time. It can happen, for instance, that someone more charismatic or clearly of higher social status than the others, influences the direction of the discussion or monopolises it. Moreover it emerged from the group interviews that discussion of automation was often seen as "imposing an issue" on participants [ ]. A focus group is a group of individuals selected and brought together by researchers in a relaxed, non-threatening setting for interactive, experience-based discussion of their perception of a given subject. The method raised difficulties for our work, but was also useful in respect of opinion polls and in-depth interviews.

21

Participants spoke with each other and exchanged ideas on specific points. In this way the group interview enables identification of changes in individual opinions initially expressed regarding information and ways of thinking put forward by the others in the course of discussion. Further, it provides a better awareness of the consistency of the opinions expressed by the interviewees. "Group dynamics" also sets up conditions conducive to a honing of personal positions and arguments. The combination of group homogeneity and interviewer empathy generates a climate of confidence favourable to spontaneous discourse [ ], that is to say, forcing them into a field which did not necessarily interest them. In this case participants have a tendency to change the subject towards one they feel more at ease with. The duration of the interviews and the verbal exchanges that took place allowed us to spot this "imposition" and reorient the discussion in a way an opinion poll cannot. It goes without saying that the groups were not created as representative samples, but rather with the aim of providing access to a stock of information shared by a relatively homogeneous group of individuals.

22

Results

]. In addition, the potential for disagreement among interviewees and for reciprocal influence in the course of discussion is enriching in terms of discourse.

The discussions recorded have a lot to tell us about perceptions of road safety and official recourse to automation. They are very informative, too, about road users, as long as we are aware that what is to be found in interviewee discourse is an "indigenous categorisation of users" of the roads [START_REF] Boussard | Catégorisation des usagers et rhétorique professionnelle. Le cas des policiers sur la voie publique[END_REF].

2010 Australasian Road Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory 4

Perception of automation hinges firstly on the interviewees' framing of the road safety issue [START_REF] Chong | Framing Theory[END_REF] : whom do they hold responsible for dangers on the roads? The recorded interchanges fit with the dominant representation in France, which consists in reducing the act of driving to good or bad behaviour [START_REF] Gilbert | When the Act of driving amounts to behaving well: on the framing of the road safety problem[END_REF]. The road safety problem is seen as the outcome of inappropriate driver behaviour, and this enables a better understanding of why public action on the road safety front puts its initial stress on penalties, education and communication. Since 2002 the automated devices, clearly classified as instruments of coercion, have proved their effectiveness, as official figures show: The number of fatalities has diminished by over 40% since 2002, and the authorities are speaking of 12 000 lives saved. Interviewees also noted as an everyday matter the drop in recorded traffic speeds: The average speed of private cars dropped by over 11 km/h on freeways and almost 15 km/h on secondary roads [26 However this system is only one among the many available to the authorities for improving road safety. Among these the interviewees, including the highway policemen, markedly stressed the value of educational tools. Even more specifically, the focus on driver behaviour led a number of intervieweeswith the traffic police once again no exception -to deny that speed caused accidents. So with speed not the cause -or not the sole cause -of the problem, automated enforcement cannot logically offer a longterm solution to the road hazard problem! ].

At the same time automated checking of red light running did not necessarily find greater favour, despite the lessons to be drawn from the existing literature [27 Description of driving behaviour provides a profile of several types of road users for whom the use of automated detection and sanctioning was more or less appropriate. In their research into police work

Boussard et al. [

]. Naturally we recorded opinions on the dangerousness of this kind of behaviour, but the interviewees, like the community association representatives group, expressed the feeling that the system was relatively pointless, the running of red lights being perceived as an infrequent problem. In addition they dismissed the argument in favour of protection for vulnerable road users on the grounds that Nantes residents are respectful towards pedestrians. Thus for reasons both general and local they did not really see the interest of the new device.

28

Road toll victims are startlingly absent from both discussions. This can be explained by the fact that the "real customers" of the professionals questioned -even if both groups find themselves involved with accident victims -are, rather, ordinary road users and maybe the offender. The discussions do, however, take the victim into account via references to "vulnerable users", these being first and foremost children. Reaching the same conclusion, members of civil society would like to see automated speed checking devices set up at points considered dangerous in the urban setting -near schools, for instance. For them it is not red light cameras that seem most useful in cities, but speed cameras. Speed in the urban setting is presented as a problem in terms of both dangerousness and frequency. This result thus highlights views of automation clearly at variance with those underlying the placement strategy for automated devices in France.

] foreground three categories or types of road users drawn up by police in the course of their everyday duties: the ordinary citizen, the offender and the victim. This typology can be compared with the types of road user outlined in focus groups including traffic police on the one hand and operatives on the other.

The recorded discussions concentrate more on the "offender" and the "ordinary citizen", with the risk that in the interviews they become -and this is especially true of the latter -the "victims" of the system. Looking beyond the systematic nature of the sanction, it is the secondary or indirect effects of the system that are foregrounded: a loss of licence points leading to loss of one's licence and even one's job. This placing of ordinary users in the role of victims is backed up by the fact that "road criminals" are not seen as particularly affected by a system primarily designed to combat everyday low excess speed offences.

Lastly, automation must be looked at in the context of the identities and practices of the groups of professionals. Professional rhetoric recorded in the discussions lays down what the "real work" of operatives is, showing how this work is affected by use of the automated system and thus raising the issue of a professional identity.

The automated radar is a tool whose introduction is by its very nature "destabilising" for the professional practice and identity of traffic police, even if the authorities have been able to present it as a technological means of resolving the difficulties of the profession. Automation reduces the administrative workload involved in ticketing, and in France its adoption was a reaction against the "leniency" that took the form of discretionary dropping of legal action and had previously both characterised the checking-sanction 2010 Australasian Road Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory 5 chain and contributed to its ineffectiveness [START_REF] Pérez-Diaz | L'indulgence, pratique discrétionnaire et arrangement administratif[END_REF] The police cannot be considered solely as a tool for application of the law. In the course of the everyday interaction between professionals and users, the former are led to distinguish between the "real customer", the "minor customer" and the "fake customer", with automatic detection devices seen as instruments for combating the bad behaviour of the last two of these three groups. The use of mobile devices, which concerns professionals more particularly, thus lowers them in the moral hierarchy of their duties. What is more, the tool in question leaves no scope for "assessing" the gravity of the offence and "explaining" it to the road user, just as it leaves the user no chance to "explain himself". All this goes counter to the "practical autonomy" of the traffic policeman, in which resides a major part of the interest his work has for him.

]. Furthermore, in that it does away with direct police intervention, automation goes counter to the ideal embodied by the "cops and robbers" notion.

And so the instrument involves the policeman in activities and methods that take him away from what he regards as his real mission; whence both the determination to entrust implementation to others -Ministry of Transport operatives, for instance, or private enterprise -and the rhetoric expended on establishing the system's "interest". Its principal interest lies, of course, in its effectiveness, but other considerations arose in the course of the discussions. For the police hierarchy the system is first of all interesting in managerial terms -personnel can be freed up for other tasks -and for the traffic police it has the effect of "guaranteeing" their interventions. Even so, for traffic policemen their "real job" remains "interception", which alone enables them to "situate" the driving act in question, "assess" the offence and broaden their "enquiries".

Unlike law enforcement officers, the automated radar device is not a core element in the context of the work of road maintenance and safety operatives. Nonetheless the discussions revealed an impact on their professional practice: naturally enough they noted a reduction in traffic speed near their work points, even if their complaints were mainly aimed at heavy trucks, whose speeds sometimes seem to them excessive and are not targeted by the automated devices, and at young road users they tend to see as "defying" the rules [START_REF] Corbett | Road traffic offending and the introduction of speed cameras in England: the first self report survey[END_REF] The operatives also find it regrettable that radar maintenance constraints are not taken into account when the devices are installed, and suggest that "the procedures should call for validation by the managing body". Speed cameras set on the median strip are more difficult to service than those next to the emergency stopping lane, and at the time the discussions were taking place, radar maintenance was being made all the more difficult by a proposed European directive to the effect that a lane should be closed when work is taking place on the median strip. Should this become law, work would take place at night in the interests of smooth traffic flow, and this was seen as yet another constraint by the operatives we questioned. Furthermore, they said, there was a danger that this would provoke aggressive behaviour towards them by road users and represent an additional cost for the public purse. As maintenance operatives cover greater distances than ordinary citizens, another significant factor in the exchanges was the greater likelihood of being sanctioned. The result was a sense of injustice.

]. Moreover, while road safety and a constant awareness of the dangers of the road certainly appear central to their professional identity, they are not receptive to the idea of automated speed traps for work points. In addition to the concern with safety, their professional identity embodies that of facilitating traffic flow: the role of the road operative is not to "annoy" the user but, on the contrary, to enable him to make the best possible use of the infrastructure; and there is, too, a fear of violent reactions directed at them by road users who fall victim to these speed cameras.

In contrast with these groups of professionals, community representatives showed no visible concern with automated detection devices. At the same time they were surprised that the state bodies in charge of the placing and installation of the devices had not seen fit to consult them as representatives of local associations. This is an indicator both of the current legitimacy of the practices of consultation and deliberation and of the fact that this new segment of public road safety policy was designed and overseen by central government bodies. In terms of the different territories concerned it involved essentially, not to say exclusively, devolved state departments, in a break with the dynamic of decentralisation and civil society involvement which had been at the core of road safety policy construction in France between 1982-2002 [31 Discussions within this group also pointed up a dual assessment of the automated system, one based on a reading of the non-specialist and local press and on personal experience. There were few allusions to the discussions in the primary groups. Whatever the actual content of press articles on speed cameras -in which the cameras are considered simultaneously as an additional tax and a tool for making traffic safer - it is known that individual readings remain selective: information going counter to the individual's notions are either ignored or discredited. As a consequence, and disregarding the accompanying advertising campaigns, the "practical", "local" perception of the system seems decisive in any understanding of the reception given it. Thus the interviews are full of local examples and specific cases experienced by the interviewees. This tends to validate our initial hypothesis, according to which the reception given the new instrument depends on everyday, personal experience.

On the other hand, the members of the fourth group seemed much less worried by the automated system and hence less critical of it. There are several possible explanations here. Firstly, the members are selfemployed and enjoy a high degree of independence in planning and carrying out their movements. They present their social environment as involving few constraints. They do not have to react to pressure from a hierarchy, and the clients they call on do not push them to break the speed limit. Most importantly, however, they have succeeded in developing strategies of adaptation which they see as effective in reducing the possible constraints caused by the radars. These interviewees have equipped their cars with the technological wherewithal for coping with the restrictions inherent in automated detection -speed governors and limiters, GPS, radar detection devices -and see themselves as thus able to compensate for the risk inherent in greater exposure to automated speed cameras.

Another interesting piece of information to be drawn from this group interview, but also to be found in the others, is a sense of impotence regarding public sector power as embodied in this new system of surveillance and enforcement. Any challenge to a sanction seems particularly complicated and unlikely to succeed. At the same time, however, they cannot envisage, as has been the case in other countries [32

Conclusion

], the presence of radars giving rise to collective action against the extension of automation or to discussion with the authorities regarding modes of deployment and sanctions. On the contrary, they see the system as encouraging individual ways and means of circumvention, which may be legal but sometimes are not: false plates, licence points bought on the Internet and vandalising of speed cameras. In this context the system comes across as capable of generating new delinquents because it fails to generate new publicspirited citizens.

Although the method used does not aim at representativeness in terms of the groups selected, it provides elements for understanding acceptance of automatic detection systems which are less well or only minimally covered by exclusive resort to opinion polls. While our analysis of the group interviews carried out points to the major acceptance indicators -reliability, effectiveness, equity, etc. -to be found in what is now the classical literature, the discussions generated have also enabled identification of other indicators and elaboration of other lines of reasoning.

Despite the results attributed to the use of this instrument -reduction of the road toll and of driving speeds in France -and acknowledged by those interviewed, our research makes it clear that for those for whom speed is not (or not the only) problem, the automated checking and sanctions system does not offer a fully satisfactory answer to the road toll issue. Denial of speed as an accident factor and the low rate of red light running are mentioned in the recorded discussions, and in some cases by traffic policemen. Moreover, automation represents only one of the many instruments available to the authorities for improving road safety, with interviewees putting the primary emphasis on educational measures. Lastly, perceptions of the system are certainly fuelled by the print and audiovisual media, which makes it relevant to develop communication strategies in parallel with coercive tactics; but perceptions are fuelled, too, by the occasional and everyday experiences of the interviewees. And so, while the effectiveness of this kind of system can be assessed in overall terms, the same cannot be said of its acceptability, which remains closely tied to interviewees' territorial and social environments.

The most unexpected result is that this instrument is perceived as destabilising for the practice and the identity of the professionals who ensure its sound functioning and guarantee its long-term effectiveness. This is the factor which influences most strongly acceptance of the devices used and the acceptability, for the professionals who were questioned, of the new uses envisaged. By contrast the two user groups seem less worried by this system. Among the explanations for this is greater adaptability to the tool in question. In the final analysis, this research brings fresh clarification of the relatively high level of acceptability of the automated checking and sanctions system applied to traffic violations in France.

2010 3 Table 1 -

 31 Australasian Road Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory The four focus groups set up in from the road traffic safety division of the Direction Départementale de la Sécurité Publique (DDSP) FO2 -traffic policeman, DDSP FO3 -traffic policeman, DDSP FO4 -Commander freeway squad, Groupement Départemental de la Gendarmerie Nationale (GDGN) FO5 -Motorcycle gendarme, GDGN FO6 -Sergeant, Motorcycle squadand safety operative, Direction Interdépartementale des Routes de l'Ouest (DIRO) AE2 -head of maintenance centre, Loire-Atlantique département AE3 -Team leader, Loire-Atlantique département AE4 -maintenance and safety operative, tenants' association -stadium watchman RA2 -Auto club chairman -retired -engineer RA3 -President tenants' association -retired -ambulance man RA4 -Chairman public transport users association driver PR2 -Commercial traveller PR3 -Maintenance technician PR4 -Director import-export company (sole employee)

  Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory 6

2010 Australasian Road Safety Research, Policing and Education Conference 31 August -3 September 2010, Canberra, Australian Capital Territory


Bouhelal Mediouny
email: bouhelal_monsef@yahoo.fr

Zeglaoui Anis
email: zeglaoui2001@yahoo.fr

Salem Haj
email: haj-salem@inrets.fr

Habib

MOTORWAY TRAFFIC CRASH PREDICTION BASED ON THE NEURONAL NETWORK APPROACH: APPLICATION TO THE RING WAY OF PARIS

Keywords: Safety, Risk analysis, ANN, traffic state clustering, fundamental diagram, linear and non linear regression

The paper focuses on the development of a Risk index model for traffic crash prediction, based on the application of a mixed approach: artificial neural networks, statistical analysis approaches. The inputs of the developed risk index model are the traffic measurements (volume and occupancy rate) and the calculated temporal left gradient. A global database including accidents and traffic measurements are used to validate the risk index model approach. The obtained results are promising while in some traffic conditions, the estimated risk index model is able to detect crash occurrence about 6 to 7 minutes prior to the crash time. This Risk index could be used as off-line safety evaluation index (evaluation process, off-line simulation) or real-time safety index monitoring for user information.

INTRODUCTION

Safety can be defined in a number of ways, including the official World Health Organisation (WHO) safety definition 'freedom from unacceptable risk of harm'. When we speak about traffic safety we usually think about accidents. Accidents can be defined as [START_REF] Keller | Materialien -Verkehrsleitsysteme im Straßenverkehr -Methodik und Geräte zu Erfassung des Verkehrsablaufs[END_REF]: "Any event that due to moving traffic at opened roads and places resulted in fatalities, injuries or/and damages". Safe road traffic is characterised, in an ideal case, by the absence of crashes, injuries and fatalities.

Accidents have a great effect on the safety of responders and on the mobility of the travelling public. Over 40,000 people are killed and 1, 7 million people injured on roads in the EU every year (ETSC, 2001). In the USA studies reported 41,000 people killed and more than 5 million injured. It is estimated that 18% of fatalities on motorways is due to secondary accidents only. Representing human life in numbers is not a favourable practice, however, the following accident cost estimates could be found in literature. In the USA, in addition to the delay costs, there is close to $200 billion per year of direct economic loss due to accidents and fatalities (FHWA, 2004). In the EU the cost to society has been estimated at 160 billion Euros annually.

In order to increase the traffic safety, control measures are introduced to improve traffic performance in motorway traffic including speed limit control, ramp metering, user information aiming at homogenizing the practical speed along the motorway sections and at minimizing the number and the severity of accidents and consequently increasing safety [START_REF] Dilmore | Implementation strategies for Real-Time traffic safety Improvement on Urban Freeways[END_REF]. On the other hand, introduction of electronics and computerization systems in the vehicle technologies have significantly contributed to safety and comfort. However, the prediction of the crash in real time is still in investigation phase and some research efforts are dedicated in this area. During the last five years, there is an increasing focus on the development of real time ("potential crash") prediction algorithm on urban motorway traffic [START_REF] Abdel-Aty | Identifying crash propensity using specific traffic speed conditions[END_REF][START_REF] Lee | Evaluation of variable speed limits to improve traffic safety[END_REF][START_REF] Salem | Risk index modeling for real-time motorway traffic crash prediction[END_REF].

In the field of safety analysis, the classical traffic evaluation approaches consist in collecting incident/accidents traffic data during the experimented scenarios (traffic control strategies, modification of the infrastructure etc.), and in proceeding to traffic impact and statistical safety analysis of the number of accidents before and after the implementation of these scenarios. Generally, the collection of the accident numbers must get a statistical significance before undertaking an evaluation process. This remark imposes a long time of field data collection (3-5 years), which is the "price to pay" for having a statistical MOSIM'10 significance of accidents set and correct safety evalu tion.

This paper aims at developing a risk index based on real data measurements, which can be used either an evaluation index during the evaluation process lea ing to the dramatically reduction of the field test periods, or in real-time like: a safety monitoring tool (e.g. safety user warning system), a multi-criterion function to be optimized in real time (safety index combined with a traffic index) within several control strategies such as coordinated ramp metering, speed limit control, route guidance, etc.

The developed index is based on the collection of mea ured traffic data synchronized with incident/accidents data on two sites in France: the urban motorway A4/A86 and the ring way of Paris. In this paper, the used data concerns the Ring way of Paris only (accidents and tra fic data measurements).

AVAILABLE TRAFFIC DATA DESCRIPTIO

Ring way of Paris description

The Corridor Périphérique (CP) consists of two parallel beltways around the city of Paris (see figure 1 having a length of some 35 km in each direction, and of the connecting radial streets. The outer motorway belt is the Ring way including a total of 70 on off-ramps in both directions. Some of these ramps are the beginning or ending points of corresponding moto ways that start from or lead to the city of Paris. The inner, signal-controlled arterial belt is the Maréchaux (BM). This paper aims at developing a risk index based on realused either off-line as an evaluation index during the evaluation process leading to the dramatically reduction of the field test periods, like: a safety monitoring tool (e.g. safety criterion function to be ptimized in real time (safety index combined with a traffic index) within several control strategies such as coordinated ramp metering, speed limit control, route

The developed index is based on the collection of measronized with incident/accidents data on two sites in France: the urban motorway A4/A86

In this paper, the used data way of Paris only (accidents and traf-TA DESCRIPTION (CP) consists of two parallel he city of Paris (see figure 1), each having a length of some 35 km in each direction, and of

The outer motorway belt is including a total of 70 on-ramps and 70 Some of these ramps are the beginning or ending points of corresponding motorways that start from or lead to the city of Paris. The controlled arterial belt is the Boulevard des way of Paris.

The Corridor Périphérique is a central highway facility de-France. It carries a wide variety of traffic types, including daily commuters, holiday traffic and commercial vehicles, and offers connections from Paris to the suburbs and vice versa, between pairs of Paris locations, and between suburbs. Moreover, the CP is used by a non negligible number of through drivers when ch their far-distance trip. CP is managed by the Paris town ters are dedicated for rapid lanes traffic management and urban traffic management. The first control centre is located in the centre of Paris (LUTECE) and it function is the urban traffic management (intersections). The second control centre is located at Porte d'Ivry and only manages the traffic on the rapid lanes (Boulevard Périphérique). It is important to note that the Boulevards des Maréchaux management is ensured by the control centre LUTECE and that a data exchange in terms of traffic states is going to be implemented in order to co ordinate the control strategies between these two central control rooms.

The Ring way represents 40% of the Parisian traffic for a network surface equal to 2.5% of the overall motorway and urban network of Paris. Périphérique is the only complete ring considered as a motorway in Ile-de-France. Linked up to 6 motorways (A1, A3; A6a, A6B, A13, A86), it supports an important national and international traffic; it is the main access to the motorways from Paris and the near suburban area. The number of vehicles served per day is equal to 1.100.000 vehicles for an average trav kilometers. The tracks represent about 10% of the nu ber of vehicles.

Data base building

Traffic dataset and accident characteristics are collected from historical database stored in the system of the Ring way. The consid equipped with real traffic measuring sensors located at around every 500 meters apart. The incidents/accidents data characteristics are automatically and manually co lected and include: time of day, location of the accident, weather conditions and severity. versa, between pairs of Paris locations, and between suburbs. Moreover, the CP is used by a non negligible number of through drivers when changing motorways on CP is managed by the Paris town-hall. Two control cenare dedicated for rapid lanes traffic management and urban traffic management. The first control centre is located in the centre of Paris (LUTECE) and its main function is the urban traffic management (intersections). The second control centre is located at Porte d'Ivry and only manages the traffic on the rapid lanes (Boulevard Périphérique). It is important to note that the Boulevards ment is ensured by the control centre LUTECE and that a data exchange in terms of traffic states is going to be implemented in order to coordinate the control strategies between these two central represents 40% of the Parisian traffic for a network surface equal to 2.5% of the overall motorway and urban network of Paris. Today the Boulevard Périphérique is the only complete ring considered as a

France. Linked up to 6 motorways A1, A3; A6a, A6B, A13, A86), it supports an important national and international traffic; it is the main access to the motorways from Paris and the near suburban area. The number of vehicles served per day is equal to 1.100.000 vehicles for an average travel distance of 7

. The tracks represent about 10% of the numraffic dataset and accident characteristics are collected from historical database stored in the HYPER operating . The considered sites are fully equipped with real traffic measuring sensors located at around every 500 meters apart. The incidents/accidents are automatically and manually col-: time of day, location of the accident, severity.

Topology of the considered stretch measurefor each crash collected traffic data covers 2 hours (one before and one after the crash) at two upstream and two downstream measurement stations (figure 2), consisting of traffic volume, occupancy rate and speed (if exists). The time The final constituted database includes the overall accidents occurred and traffic data during 4 years (2001-2004) and (2002-2004). The total number of accidents collected is around 900 on the ring way of Paris.

In order to exclude the effect of several factors, the first investigation step is made on a selected number of accidents with the following criterion: same topology (4 lanes), sunny weather conditions and full luminosities (no night-time accidents considered). Among all collected accidents, the available accidents where dramatically reduced, leading to 90 accidents selected on the Ring way of Paris.

RISK MODEL DEVELOPPMENT

The aim is to develop a crash risk function model [START_REF] Abdel-Aty | Identifying crash propensity using specific traffic speed conditions[END_REF] which is able to decide on line and at the seen of two traffic variable measurements of volume and occupancy rate, whether the traffic state is crash prone or not. For a given traffic situation, more its potential of crash occurrence increases more it's deemed to be as crash prone. The proposed crash risk function model is based on the application of a supervised learning artificial neural networks (ANN) approach. To achieve this research investigation, a labeled data base is required. Unfortunately no human expert is able to decide whether a traffic situation is crash prone or not with a high confidence in view of the partial information at disposal. To overcome this deficiency, some mathematical techniques are used, among them clustering (Kmeans) and relationship between traffic volume and occupancy rate (Greenberg fundamental diagram) are the most relevant. This investigation is implemented through three steps:

1. The measured traffic data is splitted into two categories: fluid and congested based on the fundamental diagram relationship. Two sub data sets are generated. A temporal left gradient is incorporated in each data base example to enrich the information carried by the input. 2. For each sub data set, K-Means data clustering algorithm is applied. Several experiments using different clusters are achieved to find out the best cluster number. It will be shown later that two clusters is the best data partition. 3. A majority vote was proceeded to select the class which will be labeled as crash prone. The class containing the majority of traffic patterns associated to one minute prior to the crash minute time is the crash prone class and subsequently all its elements are labeled as crash prone.

Basic theoretical risk index model development

In order to alleviate this paper, only the main approach and summary of mathematical results are described in this section.

In this research, let ܺ refers to a random vector describing the traffic state and taking its values within ℝ ௗ . For each realization ݔ of ܺ, let )ݔ(ܴ denotes the crash occurrence potential of the traffic state .ݔ A traffic condition situation ݔ is deemed to be crash prone if the risk value )ݔ(ܴ exceeds a given level α.

The following classifier holds:

)ݔ(ܻ = ቄ 1 ݂݅ ݔ ݏ݅ ℎݏܽݎܿ ݁݊ݎ 0 ݁ݏ݅ݓݎ݁ℎݐܱ = ቄ 1 ݂݅ )ݔ(ܴ > ߙ 0 ݁ݏ݅ݓݎ݁ℎݐܱ (1)
It's known that the optimal classifier approaching ܻ is the Bayes function, say ݃ * [START_REF] Devroye | A probabilistic theory of pattern recognition[END_REF], [START_REF] Hastie | The elements of statistical learning[END_REF], [START_REF] Vapnik | The Nature of statistical learning theory[END_REF]. We showed ݃ * = ܻ almost surely. In other words the Bayes loss is zero, that is ܲ(݃ * (ܺ) ≠ Y) =0.

Of course only partial information is available for traffic flow observer. We proved that under this hypothesis, the corresponding Bayes function ݃ * ෪ is the optimal approximation of ݃ * in the ܮ ଶ sense. Based on the result established by [Cybenco, G., 1989], [START_REF] Funahashi | On the approximate realization of continuous mappings by neural networks[END_REF]], [START_REF] Hornik | Multi-layer feedfowad networks are universal approximators[END_REF] concerning the density of functions implemented by neural networks within the set of classifiers, we showed that multilayer perceptrons approach the conditional probability associated to the Bayes function ݃ * ෪ and subsequently the risk function .)ݔ(ܴ

DATA LABELLING AND CATEGORIZATION

As mentioned above, no human expert can replace an oracle in terms of labeling every traffic pattern as being crash prone or not. To imitate an oracle, each pattern is labeled through the following steps:

-Building accident data series and splitting them into fluid and congested sets. -Reducing the input dimensions.

-Incorporating the temporal left-gradient in each input. -Applying K-means clustering on both fluid and congested accident data series. -A majority vote decides which cluster is crash prone or not in each set (congested and fluid).

New data base building

In the following the building up of an accident data series is detailed. For each available accident in the data set, measurements of traffic variables (occupancy rate and traffic flow) are extracted for each minute during one hour prior to the crash minute. These measurements are taken for only two stations: one upstream and one downstream of the crash location. According to the selected accidents which include only four lanes, 16 dimensional traffic patterns are built up (4 lanes * 2 stations * 2 variables) at each minute for each considered station. The sequence of these patterns makes up the accident data series.

Fluid and congested accident data series

Recall that the aim of this section is labeling data after using the clustering statistical function (K-means) which is based on grouping sample examples belonging to an Euclidian state space according to a given distance function (criterion). Generally this distance function is taken as the Euclidian distance. However, crash prone patterns could be very disparate when they correspond to fluid or congested traffic situations, which complicates the task of such clustering methods leading to unsatisfactory results. To palliate this shortcoming, accident data series are categorized into fluid or congested series using the Greenberg fundamental diagram relationship [START_REF] Greenberg | An analysis of traffic flow[END_REF], [START_REF] Lighthill | On Kinematic waves, II. A theory of traffic flow on long crowded roads[END_REF].

For every accident data series, for each underlying station and for each dummy lane, pairs of (,

)
where k is the occupancy rate and q is the traffic volume are extracted. The Greenberg relationship is fitted to the data set of (, ) yielding an estimated fundamental diagram. Figures (,,,

K-means based data labeling

The accident data series are splitted into fluid and congested series. Each traffic pattern belonging to a series is an eight dimensional input. At this stage, a temporal left gradient is added to every sample example to take into account the time varying of the measurements and hence a 16 dimensional input is obtained. The gradient is computed using the values of ݇ and ݍ at minutes ݐ and ݐ( -1) for each dummy lane at each station. Recall that each input contains measurements associated to one upstream station and one downstream station with respect to the location of the crash for each lane. This structure can be considered as a spatial gradient. The injected temporal left gradient enriches the information carried by each input. At the end of this stage, two categories of data are created. The first one contains the whole 16 dimensional examples deriving from fluid accident data series and referred to as fluid category. In the same way, the congested category is created from the congested accident data series.

On each above category, a K-means clustering is applied. Experiments were led using different numbers of clusters ܭgoing from two to five. The best configuration is selected upon the mean and the standard deviation of silhouette patterns. The silhouette displays a measure of how close each point in one cluster is to points in the neighboring clusters. This measure ranges from -1 to +1. The +1value indicates points that are very distant from neighboring clusters. The 0 value indicates points for which no decision can be taken. The -1 value indicates points that are probably assigned to the wrong cluster. More the mean silhouette clustering is large and its standard deviation is small more the clustering is better. The Recall that the aim of K-means is to be able to label each example as crash prone or not. The main idea of this labeling is: if there are precursors to a crash they would be detected at least through the traffic measurements of one minute prior to the minute of accident occurrence. Therefore the cluster containing the majority of patterns related to 59 minute will be considered as crash prone.

All examples belonging to that cluster will be labeled so.

The remaining patterns are non crash prone. The next step is merging all crash prone examples deriving from fluid and congested categories in a unique crash prone class. Similarly, non-crash prone class is built up. Approximately two thirds of the overall examples are in the non crash prone class. The target of each pattern is either +1 or -1 according to whether it is crash prone or not.

ANN architecture investigation

The best architecture (the best number of hidden units ݇) is determined experimentally according to the available training and validation sets. Several configurations were tested with ݇ going from 5 to 50. To evaluate the efficiency of each MLP, the correlation coefficient ܴ is computed. This coefficient corresponds to the linear regression of the MLP outputs on their associated targets. Experiments show that the best architectures seem to be those with hidden unit number between 20 and 30.

Behavior of the risk index

This subsection is devoted to test the ability of the risk function implemented by the selected MLP to evaluate the crash proneness. Also, the behavior in time of this estimated risk function is studied during a period of ten minutes prior to the crash time. These experiments are achieved using the data series of the test set made up previously.

Due to the previous architecture investigations, an MLP with ݇ = 21 hidden nodes is chosen. Let ݔ denotes the input of the MLP and )ݔ(߮ its output. A traffic situation described by its input ݔ (measurements and temporal left gradient) is considered to be crash prone if )ݔ(߮ > 0 and non-crash prone if ߮ )ݔ( ≤ 0. This choice is based on both target labels ሼ-1,1ሽ and the theoretical risk index model development. On the other side, accident data series of each category (fluid and congested) are handled separately. For each data series belonging to the fluid category, the average of MLP outputs for the same minute is evaluated. This process is repeated for the ten minutes prior to the crash time. In the same way an average of MLP outputs is computed for the same period and for the data series belonging to the congested category. Figures (, ) In the congested case, the estimated mean risk function is positive for about 6 to 7 minutes prior to the crash occurrence. Also, one could see that is an increasing function of time attaining its maximum just before the accident moment. However in the fluid case, the MLP decides that the traffic situations are non-crash prone during all the considered period except the last minute for which the output of the MLP is slightly positive.

CONCLUSION AND NEXT STEPS

It appears from the above results that in the congested case, the estimated mean risk function developed in this paper is able to predict accident of each traffic situation using the measurements of the traffic volume and occupancy rate. The information carried by these two variables at two successive stations and the computation of the temporal left gradient at each of them contain enough information about the real traffic state. However in the fluid case, the information carried by the input measurements is not sufficiently pertinent. The estimated risk index model predicts the accident occurrence only one minute prior to the crash time. This seems to be acceptable because in the fluid case, traffic flow and occupancy rate measurements are probably not sufficient to explain the crash occurrence. Also the one minute interval time of measurements seems to be too large and the traffic measurements are much smoothed leading to the elimination of the traffic variability. However, additional information such as driver behavior, weather conditions and speed measurements could be useful to improve the Risk index model and the crash prediction mainly in the fluid case of traffic.

ACKNOWLEDGEMENT

Bouhelal M. and Zéglaoui A. gratefully acknowledge Professor M. Masmoudi from University Paul Sabatier of Toulouse (France) for helpful discussions. His critical insights were especially valuable.

Figure 1 :

 1 Figure 1: Ring way of Paris. The Corridor Périphérique is a central highway facility of the extended traffic network of Ile-de ries a wide variety of traffic types, including muters, holiday traffic and commercial vehicles, and offers connections from Paris to the suburbs and vice

Figure 2 :

 2 Figure 2: Topology of the considered stretch ments for each crashThe collected traffic data covers 2 hours (one before and one after the crash) at two upstream and two downstream measurement stations (figure2volume, occupancy rate and speed (if exists). The time

  traffic measurements are equal to one minute.

Further

  , the reduction of input dimension avoiding the loss of information improves the learning of the artificial neural networks. A data analysis results demonstrated that measurements related to lanes one and two are highly positively correlated and similarly for lanes three and four. Averaging the measurements of two lanes is preferred to select one of them. Then two dummy lanes are obtained and named as lane I and lane II. The previous accident data series is henceforth consisting of 8 dimensional patterns. The data base thus obtained consists of 90 data series each of them contains 60 patterns. Hence the overall examples are 5400.

  ) indicate the nonlinear parametric regression related to the accident number 7014. In each figure, squares and asterisks represent respectively accident data and the estimated Greenberg relationship. The diamond and the circle report (, ) pairs corresponding respectively to one minute and two minutes prior to the crash time. The (, ) pair's corresponding to one minute and two minutes prior the crash time are named as data 59 and data 58. The accident data series stands for fluid, if both data 58 and data 59 related to both dummy lanes I and II at the two stations are in the fluid part of the fundamental diagram. Otherwise, this data series is set to be congested. In figures (, , , ) the data of the accident number 7014 is reported. Using the previous definition one can conclude that the associated data series is congested.

Figure 3 :Figure 4 :

 34 Figure 3: Lane I at Station 2

Figure 7 :

 7 Figure 7: Congested case. Silhouette by cluster with K=2

  Figures (ૢ, ,) represent this linear regression related to ݇ = 5, ݇ = 21 ܽ݊݀ ݇ = 50 .

Figure 9 :

 9 Figure 9: MLP with 5 hidden nodes. ܴ = 0.736

  plot the obtained results. The first figure corresponds to the congested category while the second one to the fluid case.

Figure 12 :

 12 Figure 12: Accident prediction (Congested case)

Figure 13 :

 13 Figure 13: Accident prediction (Fluid case)

Table 1 :

 1 table 1 reports the summarized results concerning the silhouette mean and its standard deviation of each category (fluid and congested) and for each cluster number. Screening the table 1, one can observe that among the four cluster characteristics the best one is the number cluster ܭ = 2.Figures (ૠ, ૡ) indicate the silhouette plots for both categories (fluid and congested) with ܭ = 2. Mean and standard deviation of silhouettes

	Clusters	2	3	4	5
	Mean (fluid)	0.371	0.321	0.368 0.325
	Std (fluid)	0.205	0.188	0.189 0.184
	Mean (congested) 0.465	0.325	0.335 0.342
	Std (congested)	0.213	0.197	0.197 0.191