Final DRAFT Multimodal Transport -Univ. Of Tulane, 15 & 16 September 2011 Publishing references : 36 TUL. MAR. L.J. __ 2012.

RELATIONS BETWEEN THE ROTTERDAM RULES AND THE CMR 1

Pr. Cécile Legros International Private Law Professor at the University of Rouen (Normandy University)-France Scientific director of the Institute of International Transport Law (IDIT)

On the 11th of December 2008 the UN General Assembly adopted the "Convention ofnContracts for the International Carrying of Goods Wholly or Partly by Sea", known as the "Rotterdam Rules". This new Convention strives to extend and modernize the existing international rules relating to contract of maritime carriage of goods. This Convention is supposed to replace The Hague Rules, The Hague-Visby Rules and the Hamburg Rules, thus achieving uniformity of law in the field of maritime carriage.

The Rotterdam Rules have been prepared in intergovernmental negotiations that lasted for over 10 years by the United Nations Commission for International Trade Law (UNCITRAL). The preparatory work on the convention was conducted by the Comité Maritime International (CMI). The final text was signed in Rotterdam in September 2009. In the meantime 23 coutries have signed the Convention2 , all together representing 25% of the world's trade. Spain was the first nation to ratify the Rotterdam Rules. This new instrument has been greated by shipowner organizations who firmly believe that this will achieve greater global uniformity for cargo liability, facilitating e-commerce through use of electronic documentation. Moreover, 'door to door' contracts involving other modes of transportation in addition to the sea-leg are included by the instrument. The Convention will come into force one year after ratification by the 20th UN Member state. Although there is reported to the widespread support for the Convention, the expectation is that it may be some time before the Rotterdam Rules enter into force. A ratification process is indeed, a long range process as the text needs to be understood and clarified 3 .

In Europe, some voices raised to oppose to such a ratification by European member states. Different arguments have been outlined 4 . One of them specially drew our attention. It concerns the possible interference between this new convention and other unimodal existing conventions, notably the Geneva convention of 1956 on carriage of goods by road 5 . This paper contemplates to analyze these arguments in the light of the multimodal provisions included int The Rotterdam Rules.

I. The issue

The Rotterdam Rules6 is a maritime convention but contains some mutlimodal aspects. It was clearly drafted to provide for a unique regime for door-to-door transport including a maritime leg (« maritime + »), which stands out from article 5 of the convention defining its scope of application.

Art. 5 -General scope of application 1 . Subject to article 6, this Convention applies to contracts of carriage in which the place of receipt and the place of delivery are in different States, and the port of loading of a sea carriage and the port of discharge of the same sea carriage are in different States, if, according to the contract of carriage, any one of the following places is located in a Contracting State: (a) The place of receipt; (b) The port of loading; (c) The place of delivery; or (d) The port of discharge. 2 . This Convention applies without regard to the nationality of the vessel, the carrier, the performing parties, the shipper, the consignee, or any other interested parties .

At first sight, this provision seems to refer only to sea carriage. But, the article must be interpreted in consideration with the definition of « contract of carriage » provided for in article 1, which requires at least a sea leg, and possibly a non maritime leg. A contract concluded by a maritime carrier offering a complete transport from a seller's plant (shipper) to a buyer's wharehouse (consignee) including a sea voyage (generally called a « door-todoor » contract) may then be governed by an unique regime, the RR.

Article 1 -Definitions 1 . "Contract of carriage" means a contract in which a carrier, against the payment of freight, undertakes to carry goods from one place to another. The contract shall provide for carriage by sea and may provide for carriage by other modes of transport in addition to the sea carriage

In particular, the non maritime leg, before the loading of the goods on the ship, or after unloading may be governed by the Rules. The following interrogation thus raises : What will be the applicable regime for the inland leg : Rotterdam Rules, derogations authorized by article 80 for volume contracts, domestic law, or other international instruments7 ? Obviously, an overlap between the RR and former unimodal conventions is likely to happen. In Europe, rose a serious concern about the application or not of the CMR convention on carriage of goods by road for the inland road leg. Why ? A rapid view on this convention may be useful to understand the issue.

The CMR convention. This convention was adopted in 1956 and at the present time, is ratified by no less than 55 states. It is principally an European convention, but not only. Its geographical scope ranges from Atlantic ocean to Pacific ocean (from Ireland to Vladivostock in eastern Russia). So it is a real international convention, even if from the american point of view this convention may look rather regional. This instrument is rather old but has proved its efficiency and is applied daily by courts in Europe and northern Asia 8 . Is is defended by shippers as well as road carriers as it is generally Final DRAFT Multimodal Transport -Univ. Of Tulane, 15 & 16 September 2011 Publishing references : 36 TUL. MAR. L.J. __ 2012. considered as a balanced text. The potential precedence of the RR over the CMR began to upset some actors of the transport world in Europe. Indeed, Rotterdam Rules have been considered as less protective for shippers and road carriers9 . Such a situation was denounced by European organizations of shippers 10 , as well as the IRU 11 . Some of the arguments developped appear to be relevant but mostly, it seems that the fear came from a certain difficulty to analyze the relevant provisions of this new instrument, which are obviously somewhat complex.

The arguments against the Rotterdam Rules. Different kind of interrogations were presented. These arguments have been synthetisized in a paper wrote by former official representative of the states in the working group who drafted the convention 12 . The aim of this paper was to clarify certain concerns raised by several declarations issued by international organizations 13 . As for mutlimodal aspects, and in particular relations with the CMR, the general feeling was that there was a risk that Rotterdam Rules encroaches on the CMR, implementing provisions considered as less protective for both shippers and road carriers. It was also denounced that, in certain situations, none of them would be aware of the applicable regime which could led to serious problems, notably as regards insurance. As for provisions on multimodal transport, it was held that the Rotterdam Rules provided for a lower compensation 14 . Besides, such limit would apply for domestic legs included in a doorto-door contract. Some of theses critics seem, at first sight, relevant, even if comparison between the liability limits of both instruments may be diversified. To make one's opinion on this debate, the provisions of the Rotterdam Rules relating to mutlimodal transport need now to be analyzed.

II. Analysis of the Rotterdam Rules mutlimodal aspects

Potential conflicts between Rotterdam rules and CMR may arise in two situations, treated differently by the RR :

-a road transport preceding or following a maritime leg ; -a road mode of transportation using a maritime mode of transportation : i.e. :

roll on/roll off

The two situations are dealt with respectively by article 26 and article 82 of the RR:

-article 26 provides for a general solution to conflict of conventions when the sea voyage is preceded or followed by an inland leg ; -article 82 deals with, as far as road transport is concerned, a specific situation : combined transport.

Such provisions are based upon the well known « network system ». Let us anlyse these two provisions separately.

But previously we would like to consider one question raised by the revolutionary article 80 of the Rotterdam Rules which authorizes contractual freedom for volume contracts 15 . As for the relations between this future instrument and the road convention, some authors wondered if a road leg could be governed by contractual derogating provisions under article 80. The answer seems to be no 16 . As we will see through the analysis of article 26 of the RR, some provisions of the instruments governing other modes of transportation than sea transport, prevail upon the rules provided for in this convention : provisions related to liability, limitation of liability or delay for bringing an action 17 . As far as these subjects are concerned, no derogation can be admitted on the grounds of article 41 of the CMR stating the mandatory regime of this convention 18 . As for other provisions of the RR, derogations should be valid provided that the non maritime instrument applicable authorizes such derogations. But this is not the case of the CMR convention which forbids any derogation 19 .

As a consequence, it must be concluded that no contractual freedom will be admitted for road legs, at least if the competent court is one of a state party to this convention.

Let us now examine the two relevant articles of the RR which have been drafted complementarily, article 26 and article 82.

A. Article 26 of the Rotterdam Rules 20

This provision relates to non maritime stage of transport and obviously includes road legs preceding of following a maritime transport, as indicated in the title of the article. It solves potential conflicts of conventions when a door-to-door contract has been concluded. But if separate contracts were decided for non maritime legs, the RR will not govern them. Thus, article 26 only concerns door-to-door contracts including a maritime leg.

15 Article 1 §2. "Volume contract" means a contract of carriage that provides for the car-riage of a specified quantity of goods in a series of shipments during an agreed period of time. The specification of the quantity may include a minimum, a maximum or a certain range.

Article 26 Carriage preceding or subsequent to sea carriage

When loss of or damage to goods, or an event or circumstance causing a delay in their delivery, occurs during the carrier's period of responsibility but solely before their loading onto the ship or solely after their discharge from the ship, the provisions of this Convention do not prevail over those provisions of another international instrument that, at the time of such loss, damage or event or circumstance causing delay: (a) Pursuant to the provisions of such international instrument would have applied to all or any of the carrier's activities if the shipper had made a separate and direct contract with the carrier in respect of the particular stage of carriage where the loss of, or damage to goods, or an event or circumstance causing delay in their delivery occurred; (b) Specifically provide for the carrier's liability, limitation of liability, or time for suit; and (c) Cannot be departed from by contract either at all or to the detriment of the shipper under that instrument .

Legal nature

The legal nature of article 26 has been discussed. Is it or not a provision on conflicts of conventions ? Indeed, it provides that " the provisions of this Convention do not prevail over those provisions of another international instrument …". Such wording seems to indicate that the article can be considered as a provision on conflicts of convention. The doubt raises from the fact that it refers to an hypothetical contract ("separate and direct contract with the carrier in respect of the particular stage of carriage") 21 . However, in practice, such a discussion, in spite of its theorical interest, seems useless as the effect of article 26 is the same of a real provision on conflicts of conventions : precedence of the unimodal convention over the RR. But we will see afterwards that such precedence is sometimes only partial.

Scope of application

According to this text, Rotterdam rules provisions will be ousted as far as they relate to « loss, damage or delay ». It must be deduced from such a precision that RR provisions relating to other subjects will remain applicable. The network system provided for by the convention is then rather limited 22 . But we will see later that even provisions concerning other subjects than loss, damage or delay may be ousted out by the CMR due to its mandatory character.

Conditions of application

Three conditions are required for the ousting of RR:

The first condition concerns the moment of the incident : the incident must have taken place before loading on the ship or after unloading, meaning that the maritime leg will always be governed by the Rules. during the maritime voyage, it will not fall under the scope of article 26, being considered as a maritime incident 23 .

The second condition is based upon a theoretical contract, i.e. a contract that could have been concluded for non maritime stage of transport. The international instrument governing the concerned mode of transportation (for instance, CMR for road transport) will thus be applicable provided that the situation falls within its scope of application. Cleary the incident shoud have taken place during a period covered by the other international convention. As far as road transport is concerned, it means that Rotterdam rules will be ousted by the CMR only if the road leg is international. However, application of article 26 should not depend on the interpretation of the scope provisions of other unimodal conventions. The purpose of the fiction provided for by article 26 § (b) was precisely to ensure that this article take place independently of other conventions. Thus, all domestic previous or former road transport (for instance, from Genoa to Milan24 for a sea transport coming from Houston) will remain under the scope of application of the Rotterdam Rules. More than anything, some countries have adopted the CMR for domestic law. The precedence of the RR would then ruin achievement of the unity of road transport regime 25 . Such a situation has been denounced 26 as the national law normally applicable to such a situation may have been more favourable to the parties of the contract of carriage by road.

The third condition subordinates the primacy of the other instrument to its mandatory character. As far as the CMR convention is concerned, such a requirement is obviously fulfilled as article 41 of the same convention precisely underlines its wholly mandatory character 27 .

On the basis of such conditions, we can conclude that the provisions of the CMR convention on damage, loss and delay will prevail on the RR's for the road leg as far as this leg is international. Some authors denounced the risk for a road carrier, subcontractor of a door-todoor contract, to accept nevertheless to be submitted to the Rotterdam rules 28 . But even if such a situation is surely likely to happen, I do not think this choice of law (sort of paramount clause) would be valid, at least in front of courts of states party to the CMR convention 29 . Of course, the risk is evident because, on the one hand all incident are not solved in courts, and, on the other hand, if the court is one of a state party to the Rotterdam rules and not to the CMR, such court will be likely to make the Rotterdam rules provisions prevail.

To benefit from the CMR provisions, and contrary to article 17 §1 of the Rotterdam rules which only requires the shipper to establish the loss, damage or delay, the party whishing to rely on the CMR provisions will have to establish that the event took place during the road leg. We all know, especially for container transport, that it is very hard to establish the moment when the incident occured. If it cannot be proved that the incident occured during the road leg, it seems that article 26 will not be applicable. All unlocalized loss will then always be governed by the RR.

Thus in certain situations, the CMR will be partially applicable and completed by certain provisions of the RR. On the basis of such principles a list of Rotterdam rules provisions, applicable or not to a road leg, can be made.

Classification of provisions under article 26

On the basis of the interpretation of this article, a classification of the Rotterdam rules provisions can be made, distinguishing those of the provisions overruled by the CMR provisions, and those which should remain to be applicable 30 .

Prevaling CMR provisions

The applicable CMR provisions concern first loss, damage or delay, but other provisions could however be applicable due to the mandatory character of this convention.

• Provisions on loss, delay or damage a. Dangerous goods : articles 15 (Goods that may become a danger) and 32 (Special rules on dangerous goods) will be replaced by article 22 CMR; b.

Grounds for liability : article 17 (Basis of liability) will be replaced by articles 17 and 18 CMR; c.

Delay : article 21 (Delay) will be overruled by articles 19 and 20 CMR; d.

Calculation of compensation : article 22 (calculation of compensation) will be replaced by article 23 CMR; e.

Notice in case of loss, damage or delay : art. 23 (Notice in case of loss, damage or delay) replaced by art. 30 CMR; f. Limit of liability : articles 59 to 61 (Chapter 12 -Limits of liability) replaced by articles 23 to 27 CMR.

• Other provisions

Other provisions of the Rotterdam Rules, which do not concern loss, damage or delay, should thus be applicable to road leg. However, it will not always be the case, as again, the CMR convention is wholly mandatory. For example it seems that provisions on shippers obligations 31 , on transport documents 32 , on delivery 33 or related to the right of control 34 will not be applicable the subcontractors, i.e. road carriers.

As for provisions on jurisdiction and arbitration, the situation is more complex. Chapter 14 on jurisdiction will only be applicable in relations between the maritime carrier and the shipper or consignee. In case the shipper or consignee sues directly the subcontractor, the action will be non contractual as no contractual link exist between them 35 . In such case, provisions of chapter 14 should be applicable, leading to a risk for the road carrier of pleading very far from its country36 . But if the action is brought against the road carrier on the basis of an assignment of rights from the maritime carrier to the shipper (or consignee), the action will be contractual, based upon the subcontract and then the CMR rules on jurisdiction could apply 37 . On the contrary, Chapter 15 on arbitration may not seem to be applicable as the road contract is not a contract governed by the Rotterdam Rules 38 .

Remaining Rotterdam Rules applicable provisions

Several other articles of the Rotterdam Rules will not be affected by article 26 for two differents reasons. Some provisions have no equivalent in the CMR : Articles of Chapter 4 (Obligations of the carrier) : article 11 (Carriage and delivery of the goods), 12 (Period of responsibility of the carrier), 13 (Specific obligations) ; as well as articles 18 (Basis of liability), 19 (Liability of the carrier for other persons). Others will remain efficient as they only relate to maritime stage : 14 (Specific obligations « of the maritime carrier »), 16 (Sacrifice of the goods during the voyage by sea), 24 (Deviation) and 25 (Deck cargo on ships).

Conclusion about article 26.

A rapid sight on this provision shows the complexity of this limited network system. Legal uncertainty is obvious because even if, in principle, the CMR should prevail in some situations, it seems very hard to identify such situations. Besides, though contracts of carriage of goods by road should not fall within the scope of the RR, they may be applicable to certain road legs.

Let's illustrate this complexity by a few examples :

1. A door-to-door transport from Jakarta (Indonesia) to Paris (France) including a road leg from Le Havre to Paris will be totally governed by the RR ;

2. A similar transport from Jakarta to Cologne (Germany) via le Havre, will be partially governed by the CMR for the road leg (loss, damage, delay) and partially by the RR ;

3. A transport by sea from Shangaï (China) to Hamburg (Germany), final destination Lund (Sweden), the truck being loaded on a ferry Hamburg-Malmö (Sweden), and article 66 § 1 (ii), gives jurisdiction to « The place of receipt agreed in the contract of carriage », i.e. Jakarta. The consignee may then intend to sue the carriers in front of this Court. 37 Article 31.

38 Article 75 §1.

The analysis of the paragraph concerning road transport shows its limited scope of application.

Analysis of the provision

Chapter 17 -Matters not governed by this Convention Article 82 -International conventions governing the carriage of goods by other modes of transport Nothing in this Convention affects the application of any of the following international conventions in force at the time this Convention enters into force, including any future amendment to such conventions, that regulate the liability of the carrier for loss of or damage to the goods : (a) Any convention governing the carriage of goods by air to the extent that such convention according to its provisions applies to any part of the contract of carriage; (b) Any convention governing the carriage of goods by road to the extent that such convention according to its provisions applies to the carriage of goods that remain loaded on a road cargo vehicle carried on board a ship; (c) Any convention governing the carriage of goods by rail to the extent that such convention according to its provisions applies to carriage of goods by sea as a supplement to the carriage by rail; or (d) Any convention governing the carriage of goods by inland waterways to the extent that such convention according to its provisions applies to a carriage of goods without transhipment both by inland waterways and sea .

Article 82 is included in a chapter entiltled « Matters not governed by this convention ». Thus, it clearly announces that some situations will not be governed by the Rotterdam Rules.

The very title of the article is « International conventions governing the carriage of goods by other modes of transport », which shows that this provision is clearly a conflict of convention provision, setting asite the Rotterdam Rules when another international instrument is applicable.

However, it must be noted that the precedence of other international conventions on the Rotterdam Rules are submitted to several conditions.

First, the sole conventions in force at the moment of the entry into force of the Rotterdam Rules 44 will be taken into account 45 . Possible new conventions on contract of transport of goods will then have to be compatible with the Rotterdam Rules. Such a wording is however classical for conflict of conventions provisions 46 . What is more annoying is that the article only focuses on international conventions, thus excluding other international or regional instruments. This concern is particularly pregnant as regards the European Union where transport policy is the subject of many harmonization instruments (regulations or directives), which cannot be qualified as international conventions. The adoption of the Rotterdam Rules by all European member states, or, by the European Union itself, would undoubtedly have an impact on the future European Rules on transport. Indeed, the EU White paper of 2011 entitled « Roadmap to a Single European Transport Area -Towards a competitive and resource efficient transport system » clearly quotes several times mutlimodal transport 47 . 44 Is is doubful that a new instrument would be adopted till this date, but who knows ? 45 A special reference to future amendments to such conventions however enables to extend the scope of Thus, there could be a risk that European measures could not be taken, even for exclusively intra-european relations, because of the precedence of the RR.

Second, the only conventions who will prevail on Rotterdam Rules are those « that regulate the liability of the carrier for loss of or damage to the goods ». This expression seems to exclude conventions on another subject, which is quite logical. An authorized author 48 however declared that the only purpose of the formula was to identify the pertinent conventions, but not to restrict the scope of application of article 82 49 .

I will now analyze the specific paragraph dedicated to road conventions, paragraph (b).

(b) Any convention governing the carriage of goods by road to the extent that such convention according to its provisions applies to the carriage of goods that remain loaded on a road cargo vehicle carried on board a ship;

This provision is not a general provision on conflicts of conventions which would provide for a general primacy of road conventions over Rotterdam Rules. Indeed, it focuses on specific situations, those of « goods that remain loaded on a road cargo vehicle carried on board a ship », which clearly refers to roll on/roll off transport. Article 82 then states that the road convention will be applicable, if the incident relates to liability (regime ; limitation) or time for bringning an action. As far as the CMR is concerned, it implies an international road leg. If not, the Rotterdam rules will remain applicable 50 .

This formulation is inspired by article 2, paragraph 1, of the CMR convention, which is the only provision on multimodal transport in this convention and is also limited to such situations [START_REF] Czapski | La responsabilité du transporteur routier lors du transroulage et du ferroutage[END_REF] . When the conditions are fulfilled (i.e. a truck loaded on a ship), the applicable regime will then be determined by article 2 of the CMR.

Article 2 CMR 1. Where the vehicle containing the goods is carried over part of the journey by sea, rail, inland waterways or air, and, except where the provisions of article 14 are applicable, the goods are not unloaded from the vehicle, this Convention shall nevertheless apply to the whole of the carriage. Provided that to the extent it is proved that any loss, damage or delay in delivery of the goods which occurs during the carriage by the other mode of transportation was not caused by act or omission of the carrier by road, but by some event which could only occurred in the course of and by reason of the carriage by that other mode of transportation, the liability of the carrier by road shall be determined not by this convention but in the manner in which the liability of the carrier by the other mode of transportation would have been determined if a contract for the carriage the goods alone had been made by the sender with the carrier by the other mode of transportation in accordance with the conditions prescribed by law for the carriage of goods by that mode of transportation. If, however, there are no such prescribed conditions, the liability of the carrier by road shall be determined by this convention.

The conditions of application of article 2 of the CMR are the following. First, there must be no « rupture de charge » (seemless transport), meaning unloading and reloading of the goods. Clearly, it does not apply to all mutlimodal transports, but only to cours du transport par l'un des modes de transport autre que la route n'a pas été causé par un acte ou une omission du transporteur routier et qu'il provient d'un fait qui n'a pu se produire qu'au cours et en raison du transport non routier, la responsabilité du transporteur routier est déterminée non par la présente Convention, mais de la façon dont la responsabilité du transporteur non routier eût été déterminée si un contrat de transport avait été conclu entre l'expéditeur et le transporteur non routier pour le seul transport de la marchandise, conformément aux dispositions impératives de la loi concernant le transport de marchandises par le mode de transport autre que la route. Toutefois, en l'absence de telles dispositions, la responsabilité du transporteur par route sera déterminée par la présente Convention.

The article provides that the theoretical maritime contract will be governed by « dispositions impératives de la loi concernant le transport de marchandises par le mode de transport autre que la route ». The text clearly refers to « dispositions impératives » of the law (in our case, maritime), « impératif/tive » meaning in French, mandatory. It infers that not all provisions of the law or maritime convention will be applicable, but only mandatory provisions [START_REF]For instance, a french Court of appeal decided that prescription will continue to be ruled by the CMR (art. 32) and[END_REF] . The end of the article clearly states that « If, however, there are no such prescribed conditions, the liability of the carrier by road shall be determined by this convention», i.e. CMR. Such an interpretation of the French text raises several questions. First, as maritime conventions are not in general wholly mandatory, it may be difficult to identify the provisions who can be qualified as so. Are the Hague-Visby Rules compuslory for relations issued apart from a bill of lading? [START_REF] Putzeys | Liber amicorum M. Huybrecht[END_REF] As for Rotterdam Rules, there is at he present time no official list of mandatory provisions.

But there is an hesitation relating such interpretation as the english version of article two, which is also an official version, does not seem to limit the application of maritime law to its mandatory provisions. Indeed, the english version only quotes « conditions prescribed by law » with no mention of mandatory character. This contradiction in the wording of the text is quite annoying. French case-law is rather rare ont this article but the few decisions issued always focused on mandatory provisions. Failing an official interpretation of the text 57 , it is thus generally admitted that maritime law can prevail on the CMR only if mandatory [START_REF] Putzeys | Quand la mer devient route, Liber amicorum L. Tricot[END_REF] . Even, english authors and courts adopt the interpretation of the french text [START_REF] Hill | Lloyd's of London press[END_REF] . In such conditions, it seems however that maritime conventions will not generally be considered as compulsory, especially if applicable through a paramount clause [START_REF][END_REF] . The only situation identified of a mandatory application of a maritime convention to a door-to-door road transport including a maritime leg would be the situation when a bill of lading, with no reference to a charterparty, would have been issued but not transferred, a maritime convention governing rightfully the maritime stage 61 .

Conclusion on article 82

To conclude about article 82 of the Rotterdam Rules, combined road-sea transports will continue to be governed by article 2 of the CMR, if the situation copes with the conditions of application of this provision, specially localization of the damage. But even under such article, maritime conventions are most unlikely to apply in practice. Such a conclusion may reassure European defenders of the CMR convention but I am not sure that it removes all ambiguity as even in Europe, this provision is considered as rather complex and source of legal uncertainty for the road carrier as well as the shipper, who will not be easily aware of the applicable regime 62 .

It is now time to conclude.

Conclusion

The question was, what will be the applicable regime to a road leg preceding of following a maritime transport ? Will the RR reach their multimodal ambition?

Unfortunaltely, the answer to these questions is clearly "No". Except for domestic preloading or post-loading stages of maritime door-to-door contracts, it seems to me that the aim of Rotterdam Rules, to provide for a unique regime for door-to-door contracts, has partly failed. The complexity of the relevant provisions jeopardizes legal certainty.

It so remains necessary to continue to think about a real mutlimodal instrument 63 . This is why, in a certain way, I understand the concerns expressed by European actors because within the Europen union, the adoption of such an instrument could be easier. Nevertheless, we must not forget that maritime world is much larger than Europe. If such an instrument were to be adopted, It should take into account the Rotterdam Rules if ever they enter into force.

  30 F.Berlingeri, op. cit. 31 Chapter 7 -Obligations of the shipper to the carrier : art. 27 to 34. 32 Chapter 8 -Transport documents and electronic transport records : art. 35 to 42. 33 Chapter 9 -Delivery of the goods : art. 43 to 56. 34 Chapter 10 -Rights of the controlling party : art. 50 to 56.

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  If the event occured during theses stages but lasts and is aggravated

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21

D. Glass, Meddling in the Multimodal

Muddle ? A network conflict in the UNCITRAL Draft Convention on the carriage of Goods, L.M.C.L.Q. 307, 309 (2006) ; M. Hoeks Lim, Mutlimodal carriage with a pitch of sea salt : door-to-door under the UNICTRAL Draft instrument, European Transport Law (E.T.L.) 2008, p. 270 ; J. Putzeys, op. cit. ; F. Berlingeri, D.M.F. op. cit. 22 M. Hoeks Lim, op. cit., p. 257 ; L. Rasmussen, Multimodal Aspects of the Rotterdam Rules, IRU Seminar on the Rotterdam Rules, Geneva, 3 Nov. 2010, p. 3.

  application of the article. 46 V. C. Brière : « Les conflits de conventions internationales en droit privé », Préf. P. Courbe, Bibl. de Dr. Priv., Tome 347, LGDJ, 2001. Adde, P. Reuter : « Introduction au droit des traités », Publications de l'Institut Universitaire des Hautes Etudes Internationales, Genève -PUF, 3e éd. 1995.

47

http://ec.europa.eu/transport/strategies/2011_white_paper_en.htm.

The CMR, Convention on carriage of goods by road, signed in Geneva, May 15th 1956.

Armenia, Cameroon, Congo, Democratic Republic of the Congo, Denmark, France, Gabon, Ghana, Greece,

Set forth below as "the RR".

For instance the CMR, or other conventions on air, rail or waterway transport.

See the UNIDROIT website, aiming at collecting the whole case law on the CMR issued by states party to the convention : www.unilaw.org. The website would however need to be completed and improved.

A rapid comparison on definition of loss, damage or delay, time for suit, jurisdiction can be found in W.

For instance a damage caused to a good transported under controlled temperature.

Both cities being located in Italy.

For instance see the Belgian domestic law (July 10th 1999) integrating partially CMR provisions ; Article 1 of

J. Putzeys, op. cit., spec. p. 483.

For instance, if the shipment is from Koln (Germany) to Jakarta (Indonesia) via the port of Le Havre (France),

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continuing is way to Lund by road, the Hamburg-Lund leg will by governed by the CMR.

4. But if the truck does not take the ferry but the bridge between Copenhagen (Denmark)

and Malmö, the road leg will be will be partially submitted to the CMR and partially to the RR ; 5. A transport from Jakarta to Le Havre by sea, final destination Newcastle (England) where the truck is loaded on the Channel rail shuttle between Calais and Dover, the whole carriage from Le Havre to Newcastle will also be partially submitted to the CMR and the RR ;

These examples show that the application of a single regime is a lure. Moreover, comparable situations are nevertheless ruled by different instruments. Complexity and legal uncertainty authorize to doubt about the efficiency of the RR in multimodal situations.

Let us now move to the second provision of the Rules concerning mutlimodal aspects, article 82.

B. Article 82 of the Rotterdam Rules 39

During the preparatory works of the convention, it appeared that the article 26 was unable to prevent all conflicts of conventions. A second provision was then lately drafted to complete article 26 40 .

Origin of the provision 41

In particular, article 26 was considered unlikely to avoid the risk of a possible conflict with the Montreal and Warwshaw conventions on air transport 42 , as these instruments also contain provisions on multimodal transport. First, the draft only adressed the relations between the Rotterdam Rules and the Montreal convention 43 . But later, other possible conflicts with unimodal conventions were identified, which lead to a final text tackling with all other modes of transportation. However, except for air transport where paragraph (a) provides for a general conflict rule, the final article is not general as the other instruments will not prevail as a whole on the Rotterdam Rules. The other paragraphs deal only with a specific circumstance : multimodal seemless transport (i.e. : without unloading and reloading goods). Ro/Ro transport. The CMR convention will then be applicable to international contracts concluded between a shipper and a road haulier, including a maritime (or rail : truck-on-train) transport of the vehicule (Ro/Ro traffic though the Channel sea or Mediterranean sea). Some authors consider that this provision only apply for road-sea transport (pre-carriage) and not for sea-road transport (post-carriage) 52 . I do not agree with this position because if the road haulier has concluded a door-to-door contract, I believe this provision also governs the road leg after the maritime voyage. But this assertion could be right if we imagine that no precarriage by road was performed, goods being loaded on a truck directly in the loading port. However this situation seems to me very unlikely to happen.

Second, the article is also based upon the « network system », which consists in applying to the road carrier theoretical contract provisions governing the other mode of transportation, a maritime convention in our example.

At this stage, it must be noticed that, unlike article 26 of Rotterdam rules 53 , the text mentions « the law » applicable to the other mode of transportation and not « the international instrument ». In my opinion, it means that if an international convention is not rightfully applicable to the maritime leg, the situation will be governed by the domestic maritime law designated by a conflict of laws rule [START_REF] Czapski | La responsabilité du transporteur routier lors du transroulage et du ferroutage[END_REF] .

Besides, such application of maritime law supposes on the one hand, that the origin of the incident can be identified, and, on the other hand, that the damage resulted from the maritime transport : « Provided that to the extent it is proved that any loss, damage or delay in delivery of the goods which occurs during the carriage by the other mode of transportation was not caused by act or omission of the carrier by road, but by some event which could only occurred in the course of and by reason of the carriage by that other mode of transportation ». We must at this stage notice again that these provision modifies the burden of proof. Under article 2 of the CMR, this convention will be automatically applicable except if established that the incident was exclusively linked with the maritime transport. The burden of proof will then be born by the person invoking the application of the Rotterdam Rules.

Let's take an example. If a fire occurs due to a failure of the electrical system of the truck during the maritime voyage, there is no special link between this incident an the maritime leg. But if the fire has been caused by an external event to the truck (failure of the electrical system of the holds), then the origin of the incident is linked to the maritime leg and the Rotterdam Rules will apply. Actually Rotterdam Rules should be applicable if the event occurs on board and has not been caused by the road carrier.

Moreover, there is another condition to the application of maritime conventions. Not all the provisions of these conventions will be applicable, at least if we refer to the French version of the CMR.


Paolo ; Crosetto
email: paolo.crosetto@grenoble.inra.fr

Laurent Muller
email: laurent.muller@grenoble.inra.fr

Ruffieux Bernard
email: bernard.ruffieux@grenoble-inp.fr

Bernard Ruffieux

OF-PACK LABEL: NUMBERS OR COLOURS? EXPERIMENTAL COMPARISON BETWEEN GUIDELINE DAILY AMOUNT AND TRAFFIC LIGHT IN A DIET-BUILDING EXERCICE

Keywords: JEL Classifications: D12, D18, C91, C93 PsycINFO Classifications: 3920 Nutritional labels, Food choice, Experimental Economics, Guideline Daily Amount, Traffic Lights

This paper contributes to the debate on front-of-pack nutritional labels. Because of their dissimilar formats, Guideline Daily Amount (GDA) and Traffic Light (TL) may trigger different responses among consumers. While GDA is comprehensive and cognitively demanding, information is coarser and more salient in TL. We implement an incentivized laboratory experiment to assess the relative performance of GDA and TL labelling schemes in assisting consumers to build a healthy daily diet. Participants must compose a daily diet, choosing from a finite set of products, and are paid a fixed cash amount only if the diet satisfies pre-determined nutritional goals. Goals correspond to the guideline daily amount values for different nutritional attributes, whose number varies from 1 (kcal) to 7 (kcal, fat, sugar, salt, fibre, vitamin C and calcium). Three different labels, GDA, TL and a combined GDATL are provided. Results

show that GDA performs better than TL when subjects do not face time constraints. When time is limited however, TL and GDA have identical efficacy with 4 nutritional goals, and TL even outperforms GDA with 7 nutritional goals.

Introduction

The growing awareness about the ill effects of unhealthy diets has led to the development of normative front-of-pack labels, to be added to the existing descriptive back-of-pack nutrition panels. Front-of-pack labels aim to help consumers make healthier choices. While several dozens of label formats are already in use [START_REF] Drichoutis | Nutritional Labeling, chapter 20[END_REF], the debate over their relative efficacy mainly focuses on two widespread labelling schemes: Guideline Daily Amounts (GDA) and Traffic Lights (TL). Both labels give information about the approximate amount of calories, fat, saturated fat, total sugars and salt 1 . While GDA expresses the information as percentage of a recommended daily value, TL display color-coded information using a 3-color scale (green, amber, red) derived from road lights. GDA and TL can be combined; we will refer such label in the following as GDATL. Originally called Daily Guideline Intakes by the British Food Standards Agency (1996), GDA has been recently replaced by Reference Intake 2 in the UK. The GDA system has been adopted by the Australian food and beverage industry in 2006 (Daily Intake Guide), by the European Union in 2009 as an industry standard and has been introduced in the US following Michelle Obama's initiative in 2012 (Facts Up Front). Although widespread, the GDA system may be difficult to understand for many and does not lend to quick comparisons. TL have been proposed by the British Food Standard Agency in order to make the information easily and rapidly understood. While TL are supported by the British Medical Association and welcomed by consumers, the food industry worries that foods marked red would be shunned and qualifies this system as too simplistic, misleading, patronising and unscientific.

We focus here on the mere efficiency of the label, abstracting away from exposure, perception, taste, understanding, preferences, and actual use (for recent reviews about existing research on several aspects of the relationship between consumers and labels see [START_REF] Grunert | A review of european research on consumer response to nutrition information on food labels[END_REF][START_REF] Vyth | Methodological quality of front-of-pack labeling studies: a review plus identification of research challenges[END_REF]. We implement an incentivized laboratory experiment to assess the relative performance of GDA, TL or GDATL in helping consumers build a healthy daily diet. We give the subjects clear and unambiguous nutritional goals in order to test, in a controlled environment, which label, if any, leads to the most efficient behaviour.

Many studies have fueled the debate about what format between GDA and TL should be favoured (see [START_REF] Kelly | Consumer testing of the acceptability and effectiveness of front-of-pack food labelling systems for the australian grocery market[END_REF]; [START_REF] Moeser | Simplified nutrient labelling: consumers' perceptions in germany and belgium[END_REF]; [START_REF] Grunert | Nutrition knowledge, and use and understanding of nutrition information on food labels among consumers in the uk[END_REF] for experimental studies and [START_REF] Grunert | A review of european research on consumer response to nutrition information on food labels[END_REF]; [START_REF] Hawley | The science on front-ofpackage food labels[END_REF] for reviews of the literature). While these studies are highly valuable to assess how consumers perceive, understand and use GDA and TL, they suffer from two shortcomings when it comes to the question of the labels' performance in assisting the consumer to make healthy food choices.

First, evaluations of performance are based on products rather than diet. The proclaimed objective of GDA and TL is to get consumers' overall balance right. Most experimental studies, though, implement simplified choice environments, in which consumers have to rank two or maximum three products ac-1 GDA and TL also both provide the absolute amount per serving of these categories. 2 Although the principles behind both are the same, the major difference is that GDA existed for men, women and children; there is only one set of Reference Intakes for an average adult.

2 cording to their perceived healthiness. These exercises are informative, since the aggregation of healthy products results in a healthy diet (the converse is not necessarily true, though). Nonetheless, constructing a healthy diet is a different task than facing binary choices: on a daily basis, consumers must select dozens of food items so that the sum of their nutrients meet predetermined targets. In fact, consumers are asked to perform a sort of algebraic exercise.

Second, a thorough survey of the literature reveals that the question asked determines the relative performance of the labelling schemes. Questions seem to favour TL when they are ordinal and involve small choice sets. For instance, when the subjects are asked to rank the products' relative healthiness, or to classify them into three-level scales as healthy/medium/unhealthy, TL wins (see, for instance, [START_REF] Kelly | Consumer testing of the acceptability and effectiveness of front-of-pack food labelling systems for the australian grocery market[END_REF][START_REF] Borgmeier | Impact of different food label formats on healthiness evaluation and food choice of consumers: a randomized-controlled study[END_REF]. On the other hand, questions seem to favour GDA when they are cardinal and involve large choice sets. When the subjects are asked to provide absolute assessments, i.e. to evaluate how much of a nutrient is present in each product, GDA wins (see [START_REF] Synovate | behalf of the Central Office of Information[END_REF]. This is not surprising: as already noted by [START_REF] Grunert | A review of european research on consumer response to nutrition information on food labels[END_REF] labels perform best when the question asked is the one they have been designed to answer.

Our experimental setting directly relates to the labels' primary objective: Subjects were asked to build daily menus by choosing from a large set of products and within a predetermined meal structure.

Subjects were paid if and only if the chosen menu satisfied a known and well-defined set of nutritional criteria. To guide subjects in their choices, GDA, TL or GDATL were provided. We also varied, within subjects, the number of nutritional goals. The participants faced easy, 1-dimensional tasks, in which the daily menus had to satisfy only an energy constraint; medium, 4-dimensional tasks, in which goals included energy but also limits on the amount of bad nutrients (saturated fat, sugar and salt); and difficult 7-dimensional tasks, in which on top of the above participants had also to maximise the amount of good nutrients, namely vitamin C, calcium and fibre.

The experiment was designed so that GDA and TL are only assessed on their efficacy to help consumers build a healthy daily diet. We abstract away from consideration about the salience and use of the labels in a real shopping environment. In order to observe decisions that are independent of personal taste and preferences, subjects were asked to act as hired nutritionists of a refectory that catered to all sorts of people for the whole day and earned money for each menu created that satisfied the given constraints.

The experimental task was also a simplification of the actual consumer problem. Supermarket shelves comprise thousands of products that are competing for the consumers' limited attention. Furthermore, consumers must keep a running memory of what they have bought, in order to fully take into account the overall nutritional balance of their shopping. In the laboratory, subjects are not distracted and are fully dedicated to the assigned task. Besides, we presented all information and all food choices for the whole day in one compact and intuitive screen, in order to limit the effects of working memory constraints (see a vast literature on the subject started by [START_REF] Miller | The magical number seven, plus or minus two: some limits on our capacity for processing information[END_REF]. These design choices limit the external validity of our results, but allow for a tightly controlled and neutral testing environment.

What should be expected from this experiment? The experimental setting clearly favours GDA.

Thanks to numerical information in the form of percentages, GDA is best suited to compute daily amounts. With a three-color scheme, TL gives coarser information, and is hence strictly inferior from a computing point of view since it provides three intervals rather than continuous values. Furthermore, the relative appeal of TL compared to GDA fades away in our laboratory context: subjects' attention is captured per se and monetary incentives are conducive to hard reasoning. Should GDA fail in such an environment, we could hence conclude that its application in the real world would be fragile at best. In order to be effective, GDA requires high computational skills, especially when the nutritional goals are multiple. While GDA would fit well to homo oeconomicus, TL may be more beneficial to less careful and unskilled decisions makers: TL arguably requires lower cognitive skills as it appeals to the intuitive side of human decision making. It has also been observed that too much information can lead to bad choices [START_REF] Greifeneder | Less may be more when choosing is difficult: Choice complexity and too much choice[END_REF][START_REF] Malhotra | Information load and consumer decision making[END_REF], especially if the information is multidimensional. TL labels could hence generate better results when used by cognitively constrained consumers.

We ran two different experiments with the same overall structure. In a first experiment, we give subjects unlimited time and paper and pencil to perform calculations. We recruited two different samples of subjects: highly skilled and math-oriented engineering students and a representative sample of the general population. We proposed 15 different daily diet tasks to both sets of subjects, spanning 1, 4 and 7 dimensions, and measured their performance with respect to the given task and the time spent.

Results of both the student and general population samples show that GDA performs better than both TL and the combined GDATL, on both 4-and 7-dimensional tasks. Time spent on each task is high (3 minutes on average). TL leads to slightly faster decisions than GDA, while GDATL leads to slower decisions. Both samples performed extensive computations, the main difference being that engineering students are, not surprisingly, better at constrained optimization than subjects taken from the population at large. Experiment 1 shows that GDA performs hands down better than TL. This is more the case with highly-skilled, rational engineer students than for the general population.

In a second experiment we test the robustness of these findings, and make two steps towards external validity: we imposed a time limit of 2 minutes per task and did not give the subjects paper and pencil or any other tool to perform computations. We recruited subjects from the population at large. We also added two sets of controls: two image-only tasks in which no nutritional information was given in order to examine the distance between the recommended healthy diet with diets based on subjects' (i) preference and (ii) beliefs, and two pure mathematical tasks in order to assess technical skills in simple arithmetic computations.

In Experiment 2, with 4 nutritional goals GDATL performs better than both TL and GDA, who perform equally. With 7 nutritional goals, both GDATL and TL outperform GDA. The effect is robust to controlling for subject's preferences and performance in the mathematical and preference-based tasks.

Experiment 2 shows that introducing some minor constraints to the subjects, in a setting still largely biased towards GDA, suffices to weaken the performance of GDA to the point that GDATL performs uniformly better, and TL performs equally or better depending on task complexity.

The combined results of our two experiments seem to suggest that while GDA is the right tool in the hands of unconstrained, highly-trained individuals with time, focus, and incentives, it falls short to the theoretically inferior TL as soon as some limited constraints are imposed on the subjects. While we cannot claim that our results generalize outside of the lab, we see them as a strong hint to the fact that, if GDA fails in a setting strongly biased in its favour, then it might only do worse in the case of real purchases, in which consumers are severely bounded in time, attention, focus, and budget.

Experiment 1 -Benchmark

Methods

Experimental design and treatments

The aim of the first experiment was to build a controlled environment to test the relative efficacy of three different labelling schemes (GDA, TL, GDATL) combined with three different levels of complexity (1,4, and 7 nutritional goals).

We told subjects to act as hired nutritionist of a refectory, that catered for all sorts of people for the whole day. Subjects had to compose daily diets that satisfied a set of pre-determined nutritional criteria.

They had to choose among the finite set of food items that the refectory had in store. A daily diet was made up of twelve food items laid out in a fixed French-style meal structure: breakfast, three-course lunch, afternoon snack, three-course dinner. For each component, subjects had to pick one food item out of four available alternatives. A treatment-specific nutritional label was provided for each food item.

Subjects knew from the outset that they had to repeat this task 15 times, with different products on each repetition, and that they would be paid e1.50 for each successfully completed task (i.e., if the composed daily diet satisfied all nutritional goals).

The number of nutritional goals varied from 1 to 7. In one-dimensional tasks (1D) subjects had to keep the caloric content within bounds. In four-dimensional tasks (4D), bad nutrients had to be kept below a pre-determined limit. In seven-dimensional tasks (7D), good nutrients had to be provided in sufficient amount. All constraints were set and communicated to the subjects as percentages of a daily recommended amount; their details are given in Table 1.

Dimensions Nutrient

Threshold (as % of recommended daily amount)

1D Kcal 90 ≤ ∑ Kcal ≤ 110 4D Sugar ∑ Sugar ≤ 100 Saturated fat ∑ Fat ≤ 100 Salt ∑ Salt ≤ 100 7D Fiber ∑ Fiber ≥ 100 Vitamin C ∑ Vitamin C ≥ 100 Calcium ∑ Calcium ≥ 100
Table 1: Constraints given to subjects for daily diets, by dimension Each task was displayed on a single screen. One screen contains 4 food items for each of the 12 components of the daily diet. We used 5 different screens that included different products. Each screen was repeated three times, once in 1D, once in 4D and once in 7D. The position of the food items was scrambled across repetitions to reduce the likelihood that subject recognized to be in the same screen

again. An example of nutrition screen with 4D and combined GDATL label is given in Figure 1.

Subjects had unlimited time on each screen, and were provided with paper and pencil, to allow them to take notes and/or perform computations if they wished to do so. We chose a mixed between-within design. Labels varied between subjects, while the number of nutritional goals varied within-subjects: Each subject faced only one label format, over three degrees of complexity.

Procedures and materials

We gathered full nutritional data for 346 widely consumed general food items. The nutritional data came from the Su-Vi-Max project (INSERM, 2006) 3 complemented with data from the Darmon et al.

(2009) study. We coded each food item as belonging to a food family (meat, fish, fruits, vegetables...),

and assigned it to one or more daily meals (breakfast, lunch, afternoon snack, dinner) following French eating habits. Each food item is represented by its ready-to-eat picture, centered on a neutral white background. 4Recommended daily amounts were generated from the raw nutritional data following European Union (2011) official tables, with reference to an average adult. 5 The Traffic Lights color thresholds were in turn computed from the recommended daily amount, applying a simplified version of those in force in the UK (FSA, 2013). For bad nutrients, such as salt, sugar and saturated fat, the traffic light would be green for contents lower or equal to 5% of the recommended daily amount, red for a content of more than 25%, and amber otherwise. For good nutrients such as vitamins, fiber and calcium we inverted the thresholds, assigning green to food containing more than 25% of the recommended daily amount, and red if less than 5%. This simplification was needed to give a simple and clear message to our participants, with no substantial differences with reality6 . The used threshold are summarised in Table 2.

% of recommended daily amount

5% 25% Salt Green | Amber | Red Sugar Green | Amber | Red Fat Green | Amber | Red Vitamin C Red | Amber | Green Fiber Red | Amber | Green Calcium Red | Amber | Green
Table 2: TL threshold employed in the experiment for all nutrients

We used our product database to build possible daily diets, i.e., lists of food items that make up for a full day of consumption. The daily diets were built with reference to traditional French eating habits, and were composed of a light continental breakfast, lunch (starter, main course, dessert), afternoon snack, and dinner (starter, main course, side and dessert). To balance the diet with commonly used items such as bread, oil or butter, we added to the diet a daily base composed of 120 grams of white bread, 20 grams of oil and 10 of butter. A daily diet was hence overall composed of 11 food items and a common base.

Examples of which food items were assigned to each meal are given in We randomly generated several thousand daily diets, and then checked them against nutritional criteria, with the aim of singling out both healthy and unhealthy diets. We considered a daily diet healthy if it simultaneously satisfied all 7 nutritional goals. That is, a daily diet was deemed healthy if it contained, over the 12 components, between 90% and 110% of the daily recommended amount of calories, weakly less than 100% of the daily recommended amount of salt, sugar and saturated fat, and weakly more than 100% of the daily recommended amount of vitamin C, calcium and fiber. We considered diets Unhealthy if they failed all seven criteria. After checking the diets for abnormal food items (i.e., items that would seem out of place for French eating habits), we selected 12 healthy and 12 unhealthy diets. Participants faced decision screens made of four daily diets, 2 healthy and 2 unhealthy. This generated screens made up of four columns (the four daily diets) and 12 rows (the components of a daily diet).

The information content of the screens varied across treatments. In the GDA treatment, all information was displayed as a % of the recommended daily amount of the relevant nutrient. In the TL treatment, the information appeared as color-code only. In the combined GDATL label, numerical information was shown alongside with the TL color-coding. The energy content was always expressed as % of the recommended daily amount and never as colour codes (even with TL and GDATL: As people need to take in a minimum of calories to survive, meeting the caloric constraint would not be guaranteed, unlike for bad and good nutrients, by collecting only green-patched items (see Figure 2).

We generated all the possible screens from our 24 starting daily diets, and then selected the best among them as our final decision screens. We followed two rules in this selection process. First, screens had to avoid giving the subjects "odd" choices, given the average French eating habits. An example of an "odd choice" would be to have 4 too close substitutes in the same row (4 types of bread, for example), or to have a clearly dominant option (croissants faced with three obscure substitutes). We checked the screens manually, and in all "odd" situations we dropped the screen from consideration.

Second, we checked via numeric simulation if the screens were "too easy" or "too hard" given the 1, 4 or 7 constraints. To do so, we simulated random play on the screens, and we checked the probability that a random player would satisfy the 1, 4, or 7 constraints, screen by screen. We kept only those screens that had a middle range of probability of success.

The end result of all these procedures were five final decision screens, for a total of 20 (5 × 4) daily diets and 240 (20 × 12) products. Products were not allowed to appear twice on the same screen, but could be repeated across screens. The scores of the random-play simulations on these 5 screens are given in

Incentives

Participants received a show-up fee of 10 e. On top of this amount, participants could earn additional money by correctly performing the tasks. Participants were faced with 15 choice screens: five each for 1D, 4D and 7D tasks. For each task that they completed successfully, subjects earned 1.5e. Theoretical final earnings could range from 10 to 32.5 euro, for an experiment that lasted on average one hour and a half. Participants were given no feedback about the success or failure of their tasks. The screens followed one another, and participants knew their total earnings only at the end of the experiment.

Measures

We exposed the subject to the main task described above and to a questionnaire. Our key experimental measures in the main tasks were success rate, distance, and time.

Success rate . We measure if the subject successfully created a daily diet satisfying the given constraints or not. This is a binary measure, taking values 0 or 1 for each repetition of the task for each subject.

Distance . We computed the absolute distance, in percentage points, of the subject from each target.

Any result within the target was noted as a distance of zero; farther away results were translated into positive distances. For instance, in 1D tasks, this means the distance from the 90% -110% interval set as target, and reaching both 80% and 120% means a distance of 10. Euclidean distances were used to aggregate multi-dimensional tasks.

Time . We measured the time spent on each task by each subject, in milliseconds.

Questionnaire . The final questionnaire included questions about age, gender, income, education, and a set of questions about eating habits, including snacking, the amount of money spent weekly on food, the time allocated to cooking for each meal of the day.

Results

The average results of our measures by subject pool, label and dimensions are displayed in Students are extremely good at the task. Task complexity affects the results, but in a slight way, at least for GDA tasks. Not only students diverge significantly from random play, but they get very close to submitting 100% of correct decisions in 1D tasks. The performance on 1D task is similar across and 7D tasks. TL performs significantly worse than GDA for both subpopulations. GDATL, surprisingly, performs worse than GDA, even if this difference is not significant according to a Mann-Whitney test.

Success rate is a rather poor indicator of subject's behavior, since it summarises all of the subject choices in a binary variable. We get a clearer picture analyzing the distance from the target. Figure 3, middle, reports the euclidean distance from the target for each level of complexity. Results confirm by and large the previous analysis. GDATL and GDA are not significantly different. TL performs significantly worse than GDA and GDATL in both 4D and 7D tasks and over both samples. TL performs worse by a factor of roughly 6 for students, but just of 1.5 to 2.5 for the general population.

TL leads to worse performances and to less balanced diets, but it results in faster decisions, as already highlighted by the existing literature. The results in terms of time spent on each screen are summarised by Figure 3, bottom. The amount of time spent on each task is large, up to more than six minutes on average for GDATL, 7D, and increasing in task complexity. Its magnitude is comparable across the two different samples, even though students are significantly faster. TL leads to significantly faster decisions than GDATL for students, and than both GDATL and GDA for the general population.

This analysis is confirmed by a fixed effects panel regression (Table 6) that can control for unobservable heterogeneity across subjects, and includes socio-demographic characteristics and other variables from the questionnaire.7

Table 6 shows the results of a fixed effect logit estimation for the performance and of a linear regression model for distance.

The success rate regression shows that the effect of TL is negative for both students and the general population, though with a lower coefficient for the latter. Increasing the complexity of the tasks leads to worse performances across the board. Time spent on the task slightly increases the chances of submitting a correct answer. Among the general population, females and older subjects tend to perform worse, and higher income is correlated, with a very low coefficient, with better performance. Both indicators of heating habits -the Body Mass Index (BMI) and the question about snacking -have a positive and significant coefficient, indicating that subject having worse eating habits and being overweight perform better than average in our tasks.

The distance linear probability model results are consistent with those of success rate. In this case, though, a positive distance is a bad result, so coefficient should be interpreted in the opposite way with respect to those of the performance regression. TL has increases the distance from target, as does increasing the task complexity. Income and being female have weakly significant effects. Experiment 2 -Time constraint

Methods

Experimental design

The aim of Experiment 2 was to gauge how time constraints affect the performance of labels. We introduced only three changes compared to Experiment 1. First, subjects were not provided with paper and pencil, and all scribbling and calculating on the side was forbidden. This constrained subjects to only use their working memory to perform computations. Second, subjects were given just 2 minutes to complete each task. This introduced stress, and the necessity to switch to fast heuristics rather than slow and time-consuming computations. Third, we introduced controls that were not present in Experiment 1 about preference, nutrition beliefs, and computing and cognitive skills. These changes allowed us to move in the direction of higher external validity -food shopping decisions are taken in the matter of seconds and do not usually involve large calculations -and to test the effect of cognitive limits on the efficiency of labels.

Procedures and materials

For the main diet-building task, we used exactly the same data and screens used in Experiment 1. We added one screen for two control tasks (one preference task and one health task) and two for the mathematical tasks.

Experiment 2 started with the two control tasks. Both tasks used image-only screens; that is a screen with the picture of the 4 food items for each of the components and no nutritional information (see Figure 4, top). In the preference task, subjects were asked to compose one daily diet based on their personal taste. In the following health task, subjects were asked with the exact same screen to compose a daily diet irrespective of their personal taste an that had to be 'as healthy as possible'. At the end of Experiment 2, we controlled for mathematical skills using two number-only screens, with no food name, no picture, but just numbers. These screens, introduced to the subjects as 'calculation exercises', where created using the same data and procedures of our standard diet screens (see Figure 4, bottom). In the 1D mathematical task subjects faced a screen displaying 12 rows of 4 numbers. Their task was to choose one number per row with the aim of keeping the sum of all the chosen numbers between 90 and 110. In the 4D math task, subjects faced for each cell of the table 4 numbers, labeled from A to D. They had to choose in order to make the sum of all numbers A lay between 90 and 110, and the sum of all numbers B, C, and D individually lower than 100. Finally, in between these controlling task, subjects went through 9 standard task screens, based on the same principles as in Experiment 1

Participants

A total of 174 participants took part to Experiment 2, over 14 experimental sessions. Participants were recruited from the general population using the same newspaper ads and from the existing database of potential participants as in Experiment 1. We made sure that no subject could take part in both Experiments 1 and 2, and that no INP student participated.

The experimental sessions were run in the GAEL laboratory. The experimental software and instructions introduced only slight modifications to the ones of Experiment 1, and are available upon request.

Incentives

The preference task and the health task were not incentivized. As for the main and mathematical task, incentives were the same as in Experiment 1. The only difference was that, since the number of paid screens was reduced from 15 to 11 (9 for the main and 2 for the mathematical task), we increased the payment for each successful screen to 2.5 euro. This was done also to account for the higher opportunity cost of time of the general population with respect to the earlier student sample, and to compensate the average subject for the fact that having a reduced allotted time and no pencil and paper could result in lower overall gains. With this new incentive levels, theoretical gains could vary from 10 to 37.5 euro, for an experiment that lasted on average 1 hour and fifteen minutes. As in Experiment 1, participants were given no feedback about the success or failure of their tasks. The screens followed one another, and participants knew their performance and total earnings only at the end of the experiment.

Measures

We collected the same measures of Experiment 1. On top of those, we also recorded the success rate, distance and time spent in the added mathematical and image-only tasks.

Results

Control tasks are isomorphic with the main tasks and, hence, are directly comparable. For each task, we are able to compute the average level of each nutrient and express it in percentage of the recommended daily values. We can hence assess the distance from the recommended values when (i) subjects chose according to their personal taste (in the preference task), (ii) subjects chose according to their health beliefs (in the health task), and (iii) subjects were assisted with food labeling schemes (in the main task).

Results are displayed in Figure 5, in which the shaded rectangles indicate the recommended zones.

Results show that when choosing based on their preferences (darker bars), subjects composed menus with a correct amount of calories on average, but with excessive amounts of salt (+7% with respect to the recommended daily amount), sugar (+13%) and enormous amounts of fat (+37%). The diets had enough vitamins and calcium, but lacked in fiber (-6% with respect to recommended daily amount). Simply asking the subjects to choose the healthiest possible menu (grey bars) succeeds in correcting most of the nutritional problems of the preferred diets, but only to a point. Saturated fats stayed at a level 18% higher than recommended. By and large, then, subjects could identify the healthier options in the given screen. In the following we will replicate the same analysis carried out for Experiment 1. to subjects decreases correct answers dramatically with respect to Experiment 1, and it also changes the results in terms of the best performing labels. The point estimates of the combined GDATL label are the best in both 4-and 7-dimensional tasks, even if this difference is not significant across the board, whereas its results were indistinguishable from GDA in Experiment 1. GDA and color-only TL show no difference in terms of performance, whereas TL performed much worse than GDA in Experiment 1.

Similar results are obtained in terms of distance (Figure 6, middle). The combined GDATL label performs best in both 4D and 7D tasks. In 4D tasks GDATL is the best, while in 7D it is not statistically different from TL but still significantly better than GDA.

Finally, the time spent on each screen by treatment and complexity of the task is detailed in Figure 6, bottom. The differences across treatments are much smaller than in Experiment 1, because the time limit Table 8 reports the result of the regression analysis. We replicate the same specifications and models of Experiment 1, running a fixed effect logit for performance and linear probability model for distance.

In these regressions we include also the performance in the controls, and its interactions with the label treatments. The controls are introduced via the variables maths, maths:time, preferences and health.

The variable maths is computed by summing the distance from target of both 1D and 4D mathematical tasks. The distribution of this variable is rather skewed, with a large number of zeroes since many subjects did both tasks correctly, and a large variance. maths:time simply records the sum of the time spent on both mathematical tasks. preferences measures the euclidean distance from the seven targets of subjects choices in the image-only preferences task, while health is the exact same measure for the image-only health task. Having low scores in preferences means that the subject's preferences describe a healthy diet; low scores in health means that subjects have correct nutritional beliefs about the food items, irrespective of their preferences. The two variables have a very low correlation (0.05, not significantly different from zero), meaning that subjects' preferences are not driven by health concerns, and that subjects usually change their choices when asked to chose healthy food.

The results of the fixed effect logit on success rate confirm results from point estimates and statistical testing: scaling up dimensions decreases performance, but there is no statistical difference between labels. The strong result of Experiment 1 does not exist in Experiment 2. The math control shows the expected sign -being worse in the mathematical tasks reduces the likelihood of submitting correct answer, but, interestingly, not so for TL or GDATL tasks. Individual preferences have no significant impact on success rate or distance -a result that confirms that our incentives might have crowded out preferences completely. No demographic variable has a significant impact on distance in Experiment 2.

Discussion and conclusion

The research presented in this paper stems from a basic question: which labelling scheme between Guideline Daily Amounts (GDA) and Traffic Lights (TL) is the better tool to assist consumers willing to consume healthy diets? By providing all the necessary information to compute the recommended daily amount, GDA seems better equipped than the coarser TL. Nevertheless, such computations require effort and skill, in particular when the nutritional goals are multiple. On the other hand, TL are salient and intuitive, allowing the use of simpler heuristics.

In order to address this research question, we built an artificial experimental setting that abstracts away from exposure, preference and actual choice (i.e. purchase). With aligned incentives, and full focus, subjects are asked to build daily diets that satisfy pre-determined nutritional goals. We provide an objective and controlled benchmark to test the efficacy of GDA, TL and the combined GDATL with respect to their stated goal of helping consumers build a healthy diet.

With no time constraint, Experiment 1 shows that GDA and GDATL outperform TL, irrespective of the number of nutritional goals that are simultaneously set to the subjects. Nonetheless, this result is fragile. Experiment 2 shows that setting a reasonable time constraint is enough to invalidate the previous result: TL and GDA have identical performance with 4 nutritional goals and TL even outperforms GDA with 7 nutritional goals.

Computations are key to understand these results. GDA is the right tool for decision makers that decide to compute their way out of the given task. With unlimited time and computational tools (i.e. pen and paper), the setting of Experiment 1 was ideal for GDA. The most widespread strategy in Experiment 1 was indeed to take as much time as possible, and run through all the computations. Engineering students, highly skilled in mathematics, performed about twice as good as the general population. In Experiment 2, the mathematical skills as recorded in the additional control tasks were correlated with higher success rates in GDA screens. The absence of correlation with TL and GDATL screens shows that subjects switched to heuristics other than plain computation in the presence of colour-codes in Experiment 2.

This paper contributes to the GDA and TL debate from a different perspective than the one usually adopted in the existing literature. Most studies assessing the efficacy of GDA and TL rely on choice experiments based on a very limited set of products (2 or 3 items). We instead focus on the ability of consumers to build healthy diet irrespective of their personal taste in the cleanest possible environment.

This rather artificial setting very possibly limits the direct applicability of our results to the real world. First, our environment, unlike the real world, is highly favourable to computations and, therefore, arguably best suited for GDA. Nonetheless, this choice has the advantage of enabling us to identify the upper limit of efficacy for GDA and at the same time observe how the cognitive and skill limitations of consumers might affect its performance. If GDA fails in our biased environment, with incentives and focalised attention, it cannot excel in the noisier, fuzzier, complicated real world. Second, we do not address the question of the labels' impact on consumers' preferences. In our experiments there is no actual food choice, since consumers do not buy nor will eat any of the products. One may speculate, for instance, that in real food purchases, more salient labels like TL would be better equipped to change consumers' behaviours. But such assertions will remain intuitions as far as they are not properly tested.

By providing strong evidence on the functioning of the labels in vitro, our paper sets the ground for further research on the integration of label information in actual consumer decision processes.

Figure 1 :

 1 Figure 1: Screenshot of a 4D, GDATL decision screen

Figure 2 :

 2 Figure 2: Toast & Jam: different formats for the nutritional information. 7-d not shown.

  reported in Figure3, top. The figure reports on the vertical axis the percentage of tasks correctly carried out; the error bars represent the standard error of the mean. The dotted lines in the plot represent the average expected performance of a random agent.

Figure 3 :

 3 Figure 3: Performance, distance and time, by treatment, dimensions, and subject pool

  Figure 4: The mathematical control task screens

Figure 5 :

 5 Figure 5: Mean distance from target by nutrient and task type

Figure 6 :

 6 Figure 6: Average % of correct tasks, by treatment and dimensions

Table 3

 3

	Daily base	-	120g bread, 10g butter, 20g oil
		Dessert	Fruit, sweets...
	Afternoon snack -	Sweets
		Starter	Light dishes, ham, paté...
	Dinner	Main course Meat or fish Side Vegetables, rice, potatoes...
		Dessert	Fruit, sweets...

Breakfast

Drink

Tea, coffee, milk, hot chocolate, juice...

Main course

Bread, sweets, viennoiseries... Fruit Fruit, jam... Lunch Starter Light dishes, ham, paté... Main course Sandwich, pizza, pasta...

Table 3 :

 3 The chosen structure of a daily diet, with example food items

Table 4 .

 4 Passing a single constraint (Kcal) is rather easy for a random player, but random agents have just about a chance in 30 of simultaneously satisfying 4 constraints, and one in 250 for 7 constraints (last two columns of Table4).

			Probability (%) of satisfying the constraint when playing randomly
		Kcal	Fat	Sugar	Salt	Fibre Vitamin C Calcium	4D	7D
	Screen 1 29.68 48.18 68.71 72.98 51.70	58.57	47.91	4.61 0.57
	Screen 2 32.78 57.84 70.27 58.76 51.00	48.29	40.03	4.78 0.49
	Screen 3 30.64 53.75 56.36 67.23 52.50	64.91	45.11	2.54 0.49
	Screen 4 31.87 49.03 60.71 67.56 42.14	61.39	43.69	2.98 0.30
	Screen 5 29.98 25.85 65.66 49.40 35.98	58.36	24.94	0.86 0.08
	Average	30.99 46.93 64.34 63.19 46.66	58.30	40.34	3.15 0.39

Table 4 :

 4 Performance of random players on the final screens

	Participants

We recruited participants from two distinct subject pools: engineering students from the National Polytechnic Institute of Grenoble (INP), and individuals from the general population. The INP students belong to the top-tier engineer students in France and are at ease with mathematics. Students were recruited via ads on campus and communication at economics courses at the INP. Subjects from the general population were recruited with ads on local newspapers as well as from an existing database of potential subjects in and around Grenoble.

A total of 86 subjects took part to 6 experimental sessions: 47 INP students over 3 sessions and 39 participants from the general population over 3 further sessions.

The experimental sessions were ran in the GAEL laboratory of experimental economics, located within the INP engineering school in the centre of Grenoble, France. The experimental software was programmed in PHP, and access to the source code is available upon request. The English translation of the original French experimental instructions is available upon request.

Table 5

 5

				Students		General Population
	Dimensions Treatment Success rate Distance Time (sec)	Success rate Distance Time (sec)
		GDA	0.95	0.49	82.77	0.71	3.49	118.85
	1	GDATL	0.94	0.70	85.19	0.74	3.09	172.46
		TL	0.93	0.56	89.77	0.78	3.27	120.55
		GDA	0.91	1.08	180.76	0.56	7.60	223.54
	4	GDATL	0.84	1.28	213.91	0.48	7.52	243.22
		TL	0.55	13.21	168.74	0.35	19.09	167.55
		GDA	0.86	3.23	251.81	0.41	13.06	310.47
	7	GDATL	0.78	3.01	346.44	0.29	19.54	319.77
		TL	0.36	22.28	225.10	0.12	32.52	190.78

. The formal statistical test of hypotheses, carried out using the Mann-Whitney non-parametric test, is reported in detail for all pairs of treatments in Appendix AppendixB, in Table

B

.11 for INP students and in Table

B

.12 for the general population. Differences between students and general population are significant across the board (not reported).

Table 5 :

 5 Experiment 1 main variables -treatment averagesResults are also reported in graphical form. The treatment means of the performance in the task is

  Table 7 reports the averages over treatments and dimensions of our measures: success rate, distance from target and time. The formal statistical tests over all pairwise treatment combinations for all variables are reported in Appendix AppendixB, Table B.13. Figure 6, top, reports the average success rate by dimension and treatment. Reducing the time allotted

Table 8 :

 8 As in Experiment 1, females tend to submit worse diets and age and education show similar patterns. Regression analysis of Experiment 2 -Success rate and distance form target subjects relied on other decision heuristics than outright computation when faced with color codes. According to intuition, worse performance in the health task is correlated to worse distance in the main task.

		Success rate	distance
		fixed effect logit	linear prob. model
	Constant	0.309	(0.22)	-3.549	(-0.46)
	TL	0.536	(0.98)	-5.643	(-1.85)
	GDATL	0.911	(1.57)	-6.409 *	(-1.97)
	4 dimensions	-1.990 * * *	(-12.31)	7.536 * * *	(5.98)
	7 dimensions	-3.757 * * *	(-17.56)	29.74 * * *	(22.93)
	Time	-0.00132	(-0.43)	0.0841 * * *	(4.70)
	Performance in control tasks
	maths	-0.0458 * * *	(-3.70)	0.144 *	(2.47)
	maths×TL	0.0109	(0.61)	-0.0214	(-0.29)
	maths×GDATL	0.00604	(0.36)	0.0660	(0.80)
	maths:time	0.00127	(0.39)	-0.0228	(-1.27)
	preferences	0.00665	(1.21)	0.0396	(1.30)
	preferences×TL	-0.00738	(-0.96)	0.0669	(1.55)
	preferences×GDATL	-0.00591	(-0.76)	0.0405	(0.93)
	health	-0.000796	(-0.25)	0.0962 * * *	(5.30)
	Controls
	Female	-0.623 * *	(-3.11)	0.819	(0.73)
	Age	-0.0177 *	(-2.00)	0.0464	(0.94)
	Yearedu	0.108 *	(2.25)	-0.418	(-1.57)
	Income	0.00000592	(0.06)	-0.000447 (-0.76)
	BMI	0.0149	(0.78)	0.0270	(0.26)
	Foodbudget	-0.00144	(-0.84)	-0.00142	(-0.15)
	Snacking	-0.0417	(-0.18)	1.711	(1.31)
	ln(σ 2 u )	-0.783 *	(-2.50)
	N	1846		1802
	t statistics in parentheses

The results of the distance linear probability model show a very similar pattern. When taking into account distance, though, GDATL results in significantly reduced distance with respect to the base GDA case. math is significant, but only for GDA and not for TL and GDATL treatments, indicating that * p < 0.05, * * p < 0.01, * * * p < 0.001

The Su-Vi-Max database gives the nutritional content (39 components) of 923 food items commonly eaten by French adults.

We decided to display ready-to-eat rather than packaged products to avoid trademarks and the nutritional beliefs, habits, information on prices and social desirability, that go along with them.

The full conversion table is available in Appendix AppendixA.

The actual thresholds in use in the United Kingdom (see Appendix AppendixA) slightly vary by nutrient but are by and large around the chosen 5 and 25% thresholds.

Due to a software failure, questionnaire data for students of the TL session were not recorded. As a result, the student regressions lack the demographic controls. This is a minor nuisance since the INP students are a rather homogeneous population with respect to age, revenue and eating habits.

$ We wish to thank Marie Cronfalt-Godet for excellent research support, Jean-Loup Dupuis for invaluable logistic and IT help in running the experimental sessions, and Mariane Damois for the recruitment campaign. We gratefully acknowledge the financial support of the INRA Metaprogramme DID'IT -project FOODPOL. The paper benefited from