Gilles Dufrenot

Valerie Mignon

Anne Peguin-Feissolle

Testing the finance-growth link: is there a difference between developed and developing countries?

Keywords: growth, developing countries, financial intermediation

We revisit the evidence of the existence of a long -run link between financial intermediation and economic growth, by testing of cointegration between the growth rate of real GDP, control variables and three series reflecting financial intermediation. We consider a model with a factor structure that allows us to determine whether the finance-growth link is due to cross countries dependence and/or whether it characterizes countries with strong heterogeneities. We employ techniques recently proposed in the panel data literature, such as PANIC analysis and cointegration in common factor models. Our results show differences between the developed and developing countries. We run a comparative regression analysis on the 1980-2006 period and find that financial intermediation is a positive determinant of growth in developed countries, while it acts negatively on the economic growth of developing countries.

Introduction

How much does financial development spur economic growth? Does financial intermediation affect positively the growth rate of the real GDP? Does the finance-growth link work whatever the level of development of countries? A vast empirical literature aims at providing an answer to these questions. [START_REF] Leeper | In search of the liquidity effect[END_REF], [START_REF] Roubini | Financial repression and economic growth[END_REF], King andLevine (1993a, 1993b) constitute early attempts to tackle empirically these issues. Using cross-section data, the authors conclude in favour of a positive correlation between financial intermediation and productivity growth, as well as between financial development and capital accumulation. Focusing on the issue of causality, other papers find that developed financial markets induce a strong growth and conclude in favour of bilateral causality (see, among others, [START_REF] Jung | Financial development and economic growth: international evidence[END_REF][START_REF] Rajan | Financial dependence and growth[END_REF][START_REF] Beck | Finance and sources of growth[END_REF][START_REF] Calderon | The direction of causality between financial development and economic growth[END_REF]. The possibility that financial intermediation may be beneficial to growth is also evidenced in papers using panel data. Two influential papers are [START_REF] Levine | Financial intermediation and growth: causality and causes[END_REF]'s and [START_REF] Beck | Stock markets, banks and growth: Panel evidence[END_REF]'s who report general method of moments (GMM) and dynamic panel estimates.

The significant link between finance and growth or the level of economic development is widely accepted, but the statistical evidence is based on the assumption of a uniform financegrowth nexus across countries. This hypothesis may be criticised, since there are several channels through which financial development affects economic growth. These channels have been extensively examined in the theoretical literature and include liquidity effects, financial depth, the role of financial intermediaries, and the reduced cost of information (for a survey of theoretical arguments, see [START_REF] Levine | Finance and growth: theory and evidence[END_REF]. Thus, in uncovering the effect of financial intermediation or development on the real sector, we should consider the possibility that the finance-growth nexus varies across nations. If we control for slope heterogeneity in a regression that links financial variables to growth, do we find results that confirm the wellestablished significant and positive finance-growth nexus? [START_REF] Favara | An empirical reassessment of the relationship between finance and growth[END_REF] uses dynamic specifications allowing for slope heterogeneity across countries and find results that are in contradiction with the vast literature suggesting that finance and growth are positively linked. Not only does financial development have a small effect on growth, but also the impact is negative for some combination of variables and sample periods. The variables and model used by the author are very similar to [START_REF] Levine | Financial intermediation and growth: causality and causes[END_REF]'s, but his sample is slightly larger and includes more developing countries over a longer time period. These contradictions can be due to several reasons, such as a questionable use of econometric methodologies. What is at stake here is the robustness of the tests and estimators applied when one uses panel data.

In this paper, we revisit the evidence of the existence of a long-run link between financial intermediation and economic growth, as regards these methodological problems. To this end, we focus on the issue of cointegration between the growth rate of GDP, control variables and three series reflecting financial intermediation. Using panel data, we investigate the financegrowth link in heterogeneous panels, under the assumption of cross-sectional dependence. Our methodology builds on models with an unobserved common factor structure proposed in the econometric literature to test for unit root and cointegration in panel data (see [START_REF] Bai | On the estimation and inference of a panel cointegration model with cross-sectional dependence[END_REF][START_REF] Bai | A PANIC attack on unit roots and cointegration[END_REF][START_REF] Banerjee | Breaking panel cointegration[END_REF][START_REF] Gengenbach | Cointegration testing in panel with common factors[END_REF][START_REF] Edgerton | Simple tests for cointegration in dependent panels with structural breaks[END_REF][START_REF] Hanck | Cross-sectional correlation robust tests for panel cointegration[END_REF]. The basic idea is that non-stationarity in a variable, or a combination of variables, originates from two sources: the presence of crosssectional common stochastic trends and non-stationary idiosyncratic components. The proposed methodology allows extracting the common factors and idiosyncratic components in the raw data and applying residual-based tests on the defactored data.

The remainder of the paper is organized as follows. Section 2 briefly sketches out the principles of the econometric approach to test for no-cointegration when a panel is characterized by cross-member dependence. In Section 3, we present the data, while Section 4 contains our comments of the results. Section 5 presents comparative estimations of the longrun finance-growth relationship. Section 6 concludes.

The econometric methodology

The framework considered in this paper builds on [START_REF] Bai | A PANIC attack on unit roots and cointegration[END_REF] and [START_REF] Gengenbach | Cointegration testing in panel with common factors[END_REF]. We consider a regression with a dependent variable it Y and an explanatory variable it X :

it it it X Y ε β α + + =
.

(1)

The indices i and t refer to cross-section and time-series observations, with i=1,…,N and t=1,..,T. Though we assume a bivariate system (with only one explanatory variable) for ease of exposition, the arguments can be extended to a multivariate regression. it ε is an error term that is iid. Both the dependent and explanatory variables have a factor structure: Both the common factor and idiosyncratic components are assumed to follow autoregressive processes:

X it X t X i X it it Y it Y t Y i Y it it e F D X e F D Y + + = + + = ' ' , λ λ (2)
, , , 1 , , 1 1 T t V F F V F F X t X t X X t Y t Y t Y Y t L = + Γ = + Γ = - - (3) , , , 1 , , 1 , , 1 1 T t and N i w e e w e e X it X it X X it Y it Y it Y Y it K K = = + = + = - - γ γ (4) where Y Γ , X Γ are matrices of coefficients and Y γ , X γ are coefficients. Y t V , X t V , Y it w , X it
w are respectively matrices and vectors of stationary components. Suppose that some of the autoregressive coefficients equal 1. In this case, some of the common factors and/or idiosyncratic components have a unit root. The common factors, the idiosyncratic components or both may drive the non-stationarity in the data. This implies several cases of cointegration: 1/ cointegration between the common stochastic trends of Y and X alone (that is cross-member cointegration), 2/ cointegration between the I(1) idiosyncratic components, 3/ both types of cointegration.

Standard panel unit root and cointegration tests, when applied to series with a factor structure, suffer from severe distortions and theoretical problems (see [START_REF] Banerjee | Some cautious on the use of panel methods for integrated series of macroeconomic data[END_REF][START_REF] Urbain | Spurious regression in nonstationary panels with cross-member cointegration[END_REF][START_REF] Gengenbach | Cointegration testing in panel with common factors[END_REF][START_REF] Urbain | Spurious regression in nonstationary panels with cross-unit cointegration[END_REF]. A major caveat is that the distributions of the test statistics are 'contaminated' by the presence of unit root in the factors. Recent papers on panel unit root and cointegration tests suggest working with de-factored series, which are original series from which the common factors have been removed. The procedure we employ here involves two steps.

Step 1. We first apply a PANIC analysis (panel data analysis to the idiosyncratic and common components) as proposed by [START_REF] Bai | A PANIC attack on unit roots and cointegration[END_REF]. The approach consists in testing for the presence of a unit root in the common factors and idiosyncratic components separately instead of considering the observations it X and it Y directly. Indeed, if one component is I( 1) and the other I(0), it could be very difficult to establish that a unit root exists from the original observations, especially if the stationary component is large. In this case, unit root tests on the series it X and it Y can be expected to be oversized while stationarity tests will have no power.

Step 2. ( 2a). If we detect stochastic trends among the common factors and if all the idiosyncratic components are I(0), then cointegration between it X and it Y occurs only if the I( 1) common factors of it X cointegrate with the I( 1) common factors of it Y . In this case, we have cross-member cointegration. The null of no-cointegration is tested using a Johansen type test. (2b). Suppose that both I(1) common factors and I(1) idiosyncratic components are detected. Then cointegration tests are applied separately on the common and idiosyncratic components. We conclude that it X and it Y are cointegrated if the null of no-cointegration is rejected for both the factors and the idiosyncratic components. Tests on the de-factored series (i.e. on the idiosyncratic components) are performed using [START_REF] Pedroni | Critical values for cointegration tests in heterogeneous panels with multiple regressors[END_REF][START_REF] Pedroni | Panel cointegration, asymptotic and finite sample properties of pooled time series with an application to PPP hypothesis[END_REF])'s procedures.

The data

We consider 89 countries annually observed from 1980 to 2006: 26 OECD, 21 Latin America and Caribbean (LAC), 17 Middle East and Asia (MEA) and 27 Africa. The countries are listed in Table A1, and the sources and definitions of the data are given in Table A2 in Appendix.

Financial intermediation variables. We use four measures of financial intermediation. We first consider real credit by financial intermediaries to private sector as a ratio of real GDP (CREDIT). This variable is used in [START_REF] Levine | Financial intermediation and growth: causality and causes[END_REF]. We further consider the real domestic credit by the banking sector in percentage of the real GDP (CREDBANK). The main difference with the former indicator comes from the fact that it does not isolate credit issued to the private sector. We also consider a measure of banking intermediation (BANKING) as the ratio of deposit money bank domestic assets to the sum of domestic assets from deposit money banks and central bank. The use of such an indicator was first suggested by King andLevine (1993a, 1993b) and captures the ability of commercial banks to find profitable loans more easily than central banks. As in King and Levine (1993a), we finally consider a variable of financial depth (FIDEPTH), which is the ratio of liquid asset of the financial system to real GDP.

Control variables.

The set of control variables includes a proxy for initial conditions, that is the lag real GDP per-capita (GDP(-1)), trade openness (OPEN) measured as the sum of exports and imports over GDP, a proxy of relative productivity (PROD) that is the ratio of GDP per worker for a country to the GDP per worker in the group of G7 and finally the ratio of gross domestic investment to GDP (GDI). The choice of these variables is common in the literature that explores the finance-growth nexus. Relative productivity summarizes the contribution of the quality of the factors of production to the long-run growth, while the rate of investment variable is motivated by the fact that a deeper financial intermediation leads to higher factor accumulation.

Testing for cointegration between financial intermediation and growth

Regarding the OECD countries, the application of our two-step procedure shows the existence of cointegrating relationships between financial integration and economic growth. 1 This conclusion is valid for the common components, but also when considering the idiosyncratic components. Turning to the developing countries, the main difference with the OECD countries is that we cannot find a long-run relationship between the financial intermediation and growth when considering the idiosyncratic components. This occurs because, either the idiosyncratic component of the endogenous variable is I(0) (the case of MEA and African countries), or the idiosyncratic components of the financial variables are themselves I(0) (the case of LAC countries). One can consider that common factors refer to the intra-individual dynamics, since they reflect the behaviour of something common to the countries over time. Idiosyncratic components capture the inter-individual differences. According to the above results, the developing countries are not heterogeneous enough-in terms of the financial intermediation channels that are conducive to growth-so that the time series properties of the finance-growth link may be very different from those of disaggregated data if the countries were considered individually. Considering the countries' specificities does not provide any information on the existence of a long-run relationship. Conversely, in the developed countries, there are several elements that distinguish the countries from each other. Some of these elements are of a microeconomic nature. For instance, the success of the link between financial intermediation and growth depends upon the capacities of individual firms to mobilize the available funds and transform them into profitable and innovative projects that promote growth (see, for instance, [START_REF] Rajan | Financial dependence and growth[END_REF]. Other differences among the countries come from differences in technology, profit rates, investment and demand opportunities. These create differences in the amount of financial need needed by the firms (see [START_REF] Demirgüç-Kunt | Law, finance and firm growth[END_REF]. In the developing countries, such differences are not acute since, for some of them, they rely on loans by foreign donors (the domestic banking markets are characterized by severe market frictions).

Comparing the estimates of the developed and developing countries

We now estimate the long-run relationships. We split the countries into two groups on the basis of our findings. We cannot apply the same estimators to the groups of developed and developing countries. Indeed, for the OECD countries we find cointegration relationships between both the common factors and idiosyncratic components, while cointegration is only found in the common factors for the group of MEA, LAC and African countries. In light of our discussion in the previous paragraph, for the OECD countries, we thus need an estimator involving aspects of both homogeneous behaviours (due to common factors) and heterogeneous behaviours (due to idiosyncratic components). In this respect, for OECD countries, we apply the pooled mean group (PMG) method proposed by [START_REF] Pesaran | Pooled mean group estimation of dynamic heterogeneous panels[END_REF]. It restricts the long-run coefficients to be equal across countries, but allows for short-run coefficients and variances to differ across groups. This amounts to assuming that, though the level of financial intermediation has similar effects in the long run, there are heterogeneous adjustments across countries to changes in the level of financial intermediation. For the MEA, African and LAC countries, as a consequence of our previous discussion, pooling the data yields enough information about the link between growth and financial intermediation. We thus apply the generalized method of moments (GMM) usually employed in dynamic panel models.

Let us first comment the results relating to OECD countries. Estimates of the long-run coefficients based on the PMG estimator are displayed in Table 1. Note that, although we consider short-run coefficients in the regressions, our main interest is on the long-run relationships. The short-run coefficients are considered here since they influence the estimates of the long-run coefficients. We control for the cross-sectional dependence by demeaning the data, taking each variable in deviation from its cross sectional mean. The estimates suggest that in three models out of four, the relationship between financial intermediation and growth is positive, though the elasticities seem small in magnitude. Private credit is significant only at the 10% level of confidence in model 2, but insignificant in model 4. The impact of financial depth is increased when other macroeconomic variables are appropriately controlled for. We, however, find a negative impact of banking intermediation in model 1. [START_REF] Favara | An empirical reassessment of the relationship between finance and growth[END_REF] also finds that, when using panel estimators with heterogeneous slope coefficients, the relationship between finance and growth can sometimes be puzzlingly negative. One explanation of the negative sign of the variable BANKING may be that, the size of the banking system inadequately captures the beneficial effect of financial intermediary development on growth. The financial depth seems more appropriate to measure the channels through which finance positively affects growth in the developed countries, namely the amelioration of information frictions and the reduction of transaction costs. Another explanation of the negative sign may be that the OECD sample is composed of a majority of countries with a market-based financial development. So, BANKING is not the appropriate variable.

Comparing the usual estimates found in the literature to ours, we observe that the latter are much smaller in magnitude. For instance, using a GMM estimator, [START_REF] Levine | Financial intermediation and growth: causality and causes[END_REF] obtain an elasticity of 1.52 for private credit, 2.95 for liquid liabilities and 2.43 for banking intermediation. We checked that our findings are not due to misspecifications. The models pass the h-test. Indeed a p-value greater than 0.05 indicates no significant differences between the PMG and mean group estimator, thereby suggesting that our assumption of long-run homogenous coefficient is valid. Also, the lags in our models were appropriately selected in an ADRL model using Akaike criterion. The higher magnitude of the elasticities of the financial variables obtained in the literature may come from the fact that, assuming homogeneous impact of finance on growth across countries in a dynamic model where units are heterogeneous, yields upward biased estimated. This is not to say that those results are false, but the estimates are not robust to the estimators used and the presence of idiosyncratic components can lead to misleading conclusions.

The non-financial variables, when significant, have the expected signs. We find a positive impact of the degree of openness on growth, a positive impact of productivity and of the investment rate. The lagged real GDP shows a convergence phenomenon between the OECD countries.

We now turn to the non-OECD countries. Tables 2 and3 contain the results for the developing countries. We apply a GMM system estimation by combining the regressions in differences with the regressions in levels, as suggested in [START_REF] Arellano | Another look at the instrumental variable estimation of error-components models[END_REF] and [START_REF] Blundell | Initial conditions and moment restrictions in dynamic panel data models[END_REF]. The instruments for the regressions in levels are the lagged differences of the endogenous and explanatory variables, while the instruments in the regressions in differences are the lagged values of the variables in levels. The validity of the instruments is tested using the Sargan test for over-identifying restrictions. We use a heteroskedasticity and autocorrelation consistent covariance matrix. As is seen in the Tables all the regressions pass the Sargan test, meaning that our instruments are valid. A striking difference of these regressions compared to those of the developed countries is the negative impact of the financial intermediation variables on growth in many regressions, whether or not the elasticities are statistically significant. The negative influence of the financial variables on the real economy in the developing countries is frequent in the empirical literature. This finding has received different interpretations. For instance, De Gregorio and Guidotti (1995) find a long-run negative correlation between financial development and growth in a panel data for Latin America and interpret their result as the effects of liberalization experience of the financial markets in these countries. Indeed, as noticed by the authors, during the 1970s and 1980s, Latin American financial markets were exposed to extreme conditions. In this context, according to De [START_REF] De Gregorio | Financial development and economic growth[END_REF], their results "may reflect the effects of experiments of extreme liberalization of financial markets followed by their subsequent collapse". [START_REF] Berthelemy | Développement financier, réformes financières et croissance: une approche en données de panel[END_REF] find a similar negative correlation on a panel of 82 countries over the period from 1960 to 1990. They proposed an interpretation in terms of threshold effects in the finance-growth relationship, the threshold being associated with the existence of multiple equilibria. More specifically, two stable equilibria exist: a low equilibrium such that slow growth is coupled with a weak-banking sector, and a high equilibrium such that strong growth is associated with developed financial intermediation. Between these two equilibria, an unstable equilibrium exists which determines the threshold effect of financial intermediation on economic growth. Finally, our results highlight differences among the developing countries. The financial variables are very often significant for the LAC and MEA countries (in three regressions out of four), but quite never significant for the African countries (only one regression). The financial depth seems to be the most determinant financial variable that explains the link between financial intermediation and growth.

Conclusion

In this paper, we have re-examined the question of the impact of financial intermediation on economic growth by considering the implications of cross sectional dependence in panel data. We found that this impact is explained by cross-country cointegration in the developing countries, while specific country effects also matter for the developed ones. This finding has some implications in terms of estimation. For the former, pooled-based panel data methods are indicated, while for the latter estimators allowing for possible heterogeneities among the countries are more appropriate. A comparative analysis of the regressions shows a major difference between both categories of countries. While financial intermediation variables positively influence growth in the OECD countries, they enter negatively in the financegrowth relationship for the developing countries. This calls for caution when considering panel data studies where all the countries are included in a same sample.

The present analysis can be extended in several ways. It would be interesting to consider the implications of the common-idiosyncratic decomposition in terms of regression analysis and not only in terms of cointegration testing procedures as we did here. Also, examining the issue of causality in the framework of common factor models would seem a promising approach.

Table A2. Definition of variables and sources

Financial variables

Financial depth. Ratio of liquid asset of the financial system to GDP. As in King and Levine (1993), we choose M3 or M2 if M3 is not available. The ratio is computed as follows:

( )

a

Control variables

Degree of openness. Sum of real exports and real imports as share of real per-capita GDP. Sources: WDI and OECD. Gross domestic investment (as share of GDP). Source: IFS and WDI. Relative productivity. Ratio of GDP per worker for a country to the GDP per worker in Group of Seven (G-7). Source: we collect data on labour force and GDP for each country from the Global Development Finance. We compute the ratio of GDP to labour force to obtain the GDP per worker. Real per-capita GDP. To obtain the per-capita GDP, we use a population series from the World Bank Development Indicators. To compute the real value, we use the GDP deflator and the CPI if the GDP deflator is not available. Source: WDI.

Dependent variable

Growth. First-difference of log of the real GDP.

λ

  are vectors of factor loadings. The common factors describe the behaviour of a 'representative' member of the panel, while the factor loadings capture the distance of an individual from the representative member. Y it e and X it e are idiosyncratic components reflecting the specific behaviour of an individual that is independent of the remainder of the panel.

  -of-period and average CPI and GDP is nominal GDP in local currency. Sources : -CRED = line 22D (IFS). -CPI end of period: WDI and IFS. -Average CPI: computed from the series of end of period CPI. -Nominal GDP: World Development Indicators (WDI) and International Financial Statistics (IFS).

1

  To save space, results relating to the application of the PANIC analysis, Johansen-type test and panel

	cointegration	tests	are	not	reported	but	are	available	at:	http://economix.u-
	paris10.fr/docs/302/Cointegration_tests_results.pdf.

  WDI for the developing countries. For UK and the European countries, we use M3 from Eurostat statistics until 1998 (M3 from 1998 to 2006 is based upon authors' calculation). -CPI end of period: WDI and IFS. -Average CPI: computed from the series of end of period CPI. Banking intermediation. Ratio of deposit money bank domestic assets to deposit money bank domestic assets plus central bank domestic assets. Source: IFS. Numerator = line 22 and denominator = sum of lines 22 and 12.Credit to private sector (as a ratio of GDP). Domestic credit to private sector in percentage of GDP. Source: WDI. Domestic credit by banking sector in % of GDP. The ratio is computed as follows:

			5 . 0	×	M	3	t	/	CPI	e t	+	M	3	t	1 -	/	CPI	e t -1
								t GDP	/	CPI	t
	where	e CPI and	a CPI are end-of-period and average CPI and GDP is nominal GDP in local
	currency.
	Sources :
	-Nominal GDP: World Development Indicators (WDI) and International Financial
	Statistics (IFS).
	-M2: ( CRED 5 . 0 ×	t	/	CPI	e t		+	CRED	t	-	1	/	CPI	e t -	1	)
											t GDP	/	CPI	a t
	where CRED is credit by banking sector,

Table 1. PMG estimator -Long-run coefficients

Sample 1: OECD countries Note: * Statistically significant at the 5% level of significance. ** Statistically significant at the 10% level of significance. Estimation is on demeaned data. The h-test is constructed as equivalence between the pooled mean group and the mean group estimates (see [START_REF] Pesaran | Pooled mean group estimation of dynamic heterogeneous panels[END_REF]. Probability values are provided for this test. A value less than 0.05 leads to reject homogeneity of cross-section's long-run coefficients.


Introduction

Amid the deep transformations that cities have known in the last decades, the increase of mobility practices has played a central role [START_REF] Amin | Cities. Reimagining the urban[END_REF]. As a main feature of contemporary capitalism, it notably contributes to the emergence of new forms of exchange [START_REF] Kellerman | Personal Mobilities[END_REF][START_REF] Urry | Mobilities[END_REF], which strongly articulate spatial configurations and informational devices [START_REF] Lash | Economies of Signs and Space[END_REF]. In modern urban spaces there is no distinction between, on the one hand, the ʻvirtual' world of information and the circulation of a so-called immaterial knowledge, and on the other hand, the ʻreal' world in which bodies move and material constraints are plenty. New information and communication technologies take a great part in the day-to-day organization of cities.

Actually, the articulation between places and information is not new. As [START_REF] Latour | Paris ville invisible[END_REF] showed about Paris, urban spaces are both material and informational. The city is ʻintellectual' [START_REF] Simmel | La ville[END_REF], it holds plenty of signs and inscriptions among which some were in place long before the emergence of the new technologies of information and communication [START_REF] Petrucci | Public Lettering. Script, Power, and Culture[END_REF]. The public display of signs is inherent to the organizing process of urban settings: cities are made of semiotic landscapes.

Numerous urban signs are notably a matter of wayfinding. They provide a whole graphical layer for the accountability of places and the everyday organization of public settings. Street nameplates, traffic lights or signboards inform the passerby of its own location in the city (ʻthis' neighborhood, ʻthis' street) and give indications about the suitable behavior she had to adopt (ʻstop here', ʻturn left'). By marking sites, giving places a name, designating directions, these signs are what H. [START_REF] Garfinkel | Ethnomethodology's program[END_REF] terms ʻterritorial organizational things'. They produce an ordering of the city within which ʻpractitioners are required to read descriptive accounts alternately as instructions. They do so occupationally, and as skilled matter of course, as vulgarly competent, specifically ordinary, and unremarkable worksite-specific practices. These are chained bodily and chiasmically to places, spaces, architectures, equipment, instruments, and timing'. (Garfinkel 1996: 19) In this chapter, we will study such an ordering process from an actor-network theory perspective. The strength of ANT is to enlarge ethnomethodology's program, and its definition of social order as situated accomplishments, to non-humans (Latour 2005b). Agency is always distributed between people, artifacts, and other entities such as principles or rules [START_REF] Cooren | Textual agency: how texts do things in organizational settings[END_REF]. According to this model, collectives as nations or organizations arise from heterogeneous assemblages (Latour and Weibel 2005), and cities are not organized ʻupstream', nor ordered by invisible forces. Urban spaces are the result of a continuous process carried out by day-to-day practices and mundane objects [START_REF] Farias | Urban assemblages. How Actor-Network Theory changes urban studies[END_REF]. Performation, as Latour (2005b) puts it, is a useful notion to describe such a process. It insists on the dynamic of organizing and the necessity for collective entities to be maintained day after day. Furthermore, the notion offers a multilateral view: performation processes concern sites as well as their inhabitants whose practices and attitudes are constantly shaped by their environment. The signboards or the street nameplates can thus be seen as utter components of the performation of modern public spaces. Urban signs both order physical spaces and configure the action of their dwellers.

The role of signs in the ordering process of places has already been stressed in two kinds of settings: airports and supermarkets. For the first ones, G. Fuller showed that the standardization of displayed arrows and names produces a hybrid setting within which ʻthe distinction between the building and its signs, between the text and the territory, becomes indistinct' (Fuller 2002: 236). With the airport's signage, travelers are no more explorers: invited to follow the directions of a ʻfamiliar authority', they are transformed into navigators. Within supermarkets, F. [START_REF] Cochoy | Publicizing Goldilocks' choice at the supermarket: the political work of product packaging, shopping carts, and shopping talk[END_REF] showed how things such as logos, price labels, and nutrition facts tables are key features of the consumers' choice conditions of felicity. Both the spatial configuration of shelves and these various signs displayed on products' packagings have transformed the modern customers into homo oeconomicus.

Airports and supermarkets are ʻnon-places' [START_REF] Augé | Non-Places: Introduction to an Anthropology of Supermodernity[END_REF]: they are mainly auto-referential and their organization is focused on very specific concerns. On the contrary, urban spaces are highly heterogeneous. Their graphical ordering deals with issues that largely overflow flux management or choice improvement. In this chapter, we tackle such a complexity and try to understand the way urban signs confer specific positions to the dwellers in public spaces.

Subway signs in Paris

We will focus on the case of subway signs, using the results of an ethnographical fieldwork within the Régie Autonome des Transports Parisiens (RATP). In Paris, subway signs became a central issue in the beginning of the 1990s. At that time, a team of specialists (designers, cartographers and architects) was gathered to reconsider the whole subway signs organization. Surveys, field studies and experiments were conducted. That resulted in the creation of a complete wayfinding system (a 'signage', signalétique in French) and the redaction of a particularly ambitious policy. For the first time, the content, the shape, the size, the colors and the emplacement of subway signs have been standardized and detailed in extremely precise guidelines.

In doing so, the RATP established a real ʻwriting policy' [START_REF] Foucault | Discipline and Punish[END_REF]) that deeply transformed subway spaces. Its main idea was to provide to riders as many on-the-spot instructions as they need to successfully ʻuse' the transportation network:

An electric iron, if there's nothing written on it, if there are no instructions on it, well... one does not know how it works. Here, it is the same: there are people who are moving, there are all these different spaces, one does not see what is happening behind, so our choice was to include instructions within each station. (L.T., Responsible for Signage Normalization, RATP)

There is of course an important issue here about what riders ʻneed', and more generally about who they are. Our aim is to discover which figures of users such a project conveys, that is, to identify the kind of riders this new graphical organization of subway space supposes. To understand how signage performs a specific public space, we will study it as a technology in which users' representations are inscribed. Thus, we follow S. [START_REF] Woolgar | Configuring the user: The case of usability trials, in A Sociology of Monsters: Essays on Power, Technology and Domination[END_REF] when he writes that innovation processes are ʻconfiguring the user' as much as the technology. Moreover, we adopt the position of M. [START_REF] Akrich | The de-scription of technical objects[END_REF] who showed that the innovation process could be compared to the writing of a ʻscript' that attributes tasks and positions to people and things, and organizes relations between them. As Akrich puts it, ʻtechnical objects define actors, the space in which they move, and the ways in which they interact' (p. 216). This approach is extremely useful to analyze mundane graphical devices such as wayfinding systems because, for once, it allows to go backstage and surface the work carried out behind signboards. By studying the riders' representations inscribed within signage, we can identify the behaviors supposed to take place in subway spaces, and shed the light on the ʻframework of action' (Akrich 1992: 208) that the Parisian policy of subway signs supports.

We developed a twofold methodological approach. First, we focused on internal narratives that accompany the signage policy. We conducted thorough interviews with RATP employees from the signage design and normalization department, and we systematically gathered documents that present the signage policy: the guidelines themselves, but also information leaflets, the slides of a presentation performed within the organization to announce the new signage, and articles of internal journals. If this set of data gives us access to the vocabulary used both to describe the great principles of the policy and to detail the subway signs' new organization, it also contains numerous assertions about the riders, their ʻneeds' and the ways they are supposed to use the new wayfinding system. Second, we tried to understand what it takes to follow the signage scripts in practical terms, that is, to adopt specific positions within subway spaces. In order to fully experience the scripts as frameworks of action, we had to reduce wayfinding to the sole use of subway signs, whereas ordinary riders always mobilize heterogeneous resources to find their way [START_REF] Lacoste | L'information à visage humain: la place des agents dans un système d'information-voyageurs, in Les traversées de la gare. Une méthode des trajets pour analyser l'information-voyageurs[END_REF][START_REF] Ingold | The Perception of the Environment[END_REF]. Therefore, we elaborated a phenomenological experimentation that consisted in the accomplishment of real rides within the Parisian subway system, during which we systematically gathered a picture and our comments for each board, sticker and poster we relied on to reach our destination. Since the use and the signification of the signage components were sometimes at the center of on-the-spot debates, we regularly confronted our own interpretations to take decisions and pursue our trip. This experiment offers two advantages. First, photographs are particularly useful to study visible materials [START_REF] Wagner | Visible materials, visualised theory and images of social research[END_REF]). In the case of signage, the strict ʻshooting script' we followed [START_REF] Suchar | Grounding visual sociology research in shooting scripts[END_REF] offered a means to put all the signs mobilized during a ride on the same level and to force us, as researchers, to question each of them. Second, noting our comments and debates was a rich way to surface interpretation processes, which might have remained tacit if we conducted such experiences alone. Thus, following the trail of their scripts, we studied the Parisian subway signs as organizational artifacts: we both gathered the narratives about the riders' needs and attitudes that are inscribed in them, and discovered the practical tasks their situated uses require. We identified four distinct scripts that we will detail in the next sections: information, planification, problem solving and reaction. For each one of them, we will precise the riders' definition it relies on, the type of signs that are supposed to carry it, and what it really takes in situation to follow it, that is, what one has to do to effectively become an informed rider, a planner, a problem solver or a reactive entity.

Information

In the first script we identified, the signage is conceived of as a set of tools that inform the riders. The informed rider is a familiar figure within the RATP, which has been striving for long to provide a convenient amount of information to its users. Yet, for years, the issue of information and the figure of the informed rider used to refer almost exclusively to perturbed situations. It was a crucial dimension for the service's quality that riders had to be informed each time the normal conditions of network were disturbed. In other terms, people were supposed to become informed riders only when things went wrong in the transportation network.

With the new signage policy, the informational script has been noticeably enlarged. The figure of the rider who seeks help during perturbations has been gradually completed with another one who needs to be informed continuously. Within the internal documents and during the interviews such an ordinary informed rider is omnipresent and the need for information appears as an essential dimension in the designers' definitions of subway users. But information is not mobilized as an abstract notion to describe all kinds of situations and everything subway signs have to provide. It is tightly attached to the notion of control. The informed rider is a person who tries to gain more control on the mundane circumstances of her rides.

We also have to provide riders a control of time in the course of their rides, by informing them […] about waiting time according to real traffic conditions. (RATP 1993: 14) Such a script clearly takes part in the larger historical trend of the formation of technological societies. Signage here goes with the numerous devices that transform the modes of government from surveillance to communication, where government itself ʻrelies on the existence of the informed citizen' (Barry 2001: 48). Providing information within subway spaces is a way to perform an informed rider who can fully control her displacements.

Signboards that provide information are specific ones. They are discursive, that is, they are designed to provide ʻmessages' to the riders. For example, in certain halls posters can be found that list the names of stations currently concerned by renovation works and unaccessible during a particular period. Recently, electronic real-time devices have also been put up on platforms in order to display the time remaining until the next two trains. Here, signs are mainly texts. They perform a discursive ordering of riders' environment by letting them know that ʻthis station is unavailable', ʻthe next train will be here in 8 minutes'.

Within subway spaces, to be informed, the rider has to read. This sounds obvious, but is not so: the circulation of information is never a straight and transparent operation. To read a poster's text is one thing; to make up a piece of information (and thus a resource for action) from what it is written is another. To become an informed user, not only the rider has to decipher the linguistic content of a signboard or a poster, but she also has to match this content with the actual situation (dates, places, etc.). For example, if a board displays the schedule of first and last trains according to weekdays, weekends and holidays, one has to align two things to really be informed: what the board reads and the current day and time.

Furthermore, because all information does not appear in a sole board, to become informed, the rider generally has to forge a chain of multiple readings in the course of her ride, from one discursive sign to another. In other terms, the rider does not have to simply grasp information, as it would be ʻnaturally' displayed in the surroundings. As we did several times during our rides, she has to articulate different texts and messages with her own situation, in order to produce a comprehensive informational resource.

Planification

The second script draws the figure of a pretty different rider. Here, she is staged as a person who needs to prepare her ride: she's a planner. The figure points to two distinctive dimensions. The first one is anticipation. As a planner, the rider is considered a strategic human being who makes rational projections for her future actions. The second dimension is calculation. In the documents or interviews which mention such a rider, she is conceived of as someone who collects different kind of facts (station names, lines number, connections…) and computes all these data to produce an operative scenario. The planner translates her displacement (ʻto go to this particular place') into a point-by-point itinerary, using several calculative operations.

At home or at work, riders have a lot of tools at their disposal to plan their trips before they enter into a subway station. But the RATP signage policy aims to provide specific devices that can be consulted in situ. These devices, such as maps or timetables, display abstract representations. They offer a simplified panoramic view of the network that makes its spatial characteristics (stations geographical position, trains route) and its temporal ones (timetables and frequency of trains) commensurable. These signage components perform a calculable setting. For example, timetables support the organization of a trip by anticipating the time of departure and the potential connections to reach the final destination.

Although one could think so, such devices are not identifiable to ʻcognitive artifacts' [START_REF] Norman | Cognitive artifacts, in Designing Interaction: Psychology at the Human-Computer Interface[END_REF]: they do not produce calculation themselves, contrary to the altitude alert system that E. Hutchins (1995b) described for example. The planification work largely remains on the rider's side.

A map is still an information system that forces the person to work. […] The map tells you everything and nothing at the same time, that is: you have to find the map's instructions, you have to find your departure point, you have to find your arrival point and then manage to understand everything that we put in the map… to see the connections, and this and that... (Q.W., Responsible for Cartography Department, RATP)

During our phenomenological experimentation, we decided to do unusual rides in regard to our regular experience of the Parisian subway network. These cases always began in front of a map by struggling with the multitude of signs in order to anticipate the lines and connections that would be relevant to reach the final destination we chose. Such a script puts the rider in the same position that the person L. Suchman imagined for her well-known example of rapids' run, who ʻsits for a while above the falls and plans [her] descent' (Suchman 2007: 72). The location of the specific signage components, supposed to equip the rider planner, plays an important role to perform such an anticipatory operation. Timetables and maps are essentially displayed within halls and not corridors or staircases.

However, subway stations are not rapids. First, planning cannot be done from a geographical position that overhangs the entire landscape. In subway systems, the rider is never ʻabove the falls', she can never watch the whole settings of her future displacements. For planning, she faces graphical representations from which she gathers specific kinds of instructions. As opposed to the canoe driver, she has no means to plan ʻI'll get as far over to the left as possible, try to make it between those two large rocks' (Suchman 2007: 72). The rider only knows that she has to ʻtake line 2 towards Nation, change at Saint-Lazare for line 3 towards Pont de Levallois, and stop at Wagram'. Second, because of the semiotic nature of planning devices, the rider cannot completely ʻabandon the plan and fall back on whatever embodied skills' (Suchman 2007: 72). When in corridors, she will no longer have access to the rich representation of maps and timetables. In a way, the signage radicalizes the frontier between places (and times) where riders can plan and places where they have to move. The success of their rides depends then both on the memorization of the instructions that compose their plans and on their ability to locally understand the indexicality of each sign.

Problem solving

The third script involves a rider who has problems to solve. Here, the figure is drawn from a micro-level perspective and refers to the description of each ride as a series of choices to be made. But these choices are more like dilemmas than options. The rides are not peaceful and the problem solver figure is mainly a worried person. Subway spaces are presented as real labyrinths that put the riders in a state of maximal uncertainty. The problem solver, as she moves, is assailed with questions:

Where can I make a phone call? Where can I buy a ticket? Which bus should I Take? On her path, at each moment, the rider wonders. (RATP 1997: 2) The aim of signage here is to give to the rider every possible means to get out of what is presented as her ʻnatural' state of indecision. Thus, if the figure of problem solver is imported from the cognitive sciences where it is central [START_REF] Simon | Foundations of Cognitive Science[END_REF], it is actually far from their mentalist perspective. For the signage designers, the graphical objects put in the environment are conceived of as external resources that should help the rider in search for a solution. Here, the problem-solving operations are then inscribed within a large cognitive system. Cognitive tasks are distributed between humans and artifacts (Hutchins 1995a) and do not depend on a sole individual engaged in a self-reflexive deliberation. As the responsible for signage normalization told us, within subway stations, the signage and the riders are supposed to ʻwork hand in hand'. If we focus on the figure of the rider, that means that she is performed as an equipped person: confronted to a multitude of choices, she is supposed to take a significant advantage by delegating some solutions to signboards, instead of thinking by herself.

The signs that support this figure are mainly the directional ones. They display both places' identifications (lines' numbers, destinations, streets' names) and arrows. They play a crucial role in the ordering of spaces by marking the links between sites. Their presence performs a hybrid environment [START_REF] Fuller | The arrow-directional semiotics: wayfinding in transit[END_REF] that is as well architectural as cognitive: a setting that supports decision-making. In a way, associated to the figure of problem solver, what the signage does to the subway spaces can be compared to what F. [START_REF] Cochoy | Is the modern consumer a Buridan's donkey ? Product packaging and consumer choice[END_REF] showed about the packaging in grocery stores: not only it provides the resources to decide but it performs the conditions for the choice itself.

[With signage], at any time one is confronted to a choice that divides the universe in two parts: what can be reached by turning left and what can be reached by turning right. Then, one direction of our system applies to half of the space and the other direction applies to the other half. (L.C., Information Systems & Telecommunications Department, RATP) But the felicity of such an ʻequipped choice' setting cannot be understood with the sole vocabulary of the distributed cognition model. If signboards are clearly designed to become cognitive resources, they are, in the same time, constituted as constraints. In the performation process we try to describe here, both the environment and the riders are shaped. Not only is the rider invited to rely on various signs during her displacement; she is also invited to mobilize them in a certain manner. This is extremely clear for the problem solver figure for which some signs are designed in order to bypass any deciphering operation at a certain distance. Words that appear on them are made to be spot, not read:

The important thing is that a destination is a shape that I spot. That is: it is clear that ʻNeuilly' and ʻChateau de Vincennes' cannot have the same shape. And to do this, we need to write in capital letters and lower-case letters on the one hand, and to reduce the letters height on the other hand, in order to obtain what's absolutely necessary to be seen, to be read when one stands from a certain distance and beyond the shape of words becomes imperative. (L.C., Systems & Telecommunications Department, RATP) This last point stresses an important feature of the problem solving script. During some parts of our rides, our choices have to be made not in deciphering messages but in spotting specific signs and recognizing ʻoutlines of drawn words' (RATP 2002: 15 [slides]). In order to become an equipped rider, one then has to leave some habits behind, which is a real competency. Here, one has to accept not to read.

Reaction

The last script defines the rider as a reactive entity. Neither in a position of control, nor in a situation of uncertainty, she is staged as a person who goes smoothly through corridors, halls and platforms, almost without thinking. She does not have any imperative for organizing her trip in advance and does not engage in self-reflexive deliberations. Intensely aware of the surroundings, she is mostly reactive. The rider is here driven by basic automatic reflexes:

No sooner seen than glimpsed… […] All the signs that compose the new signage are taken at first glance. The repertoire is mostly constituted of signs that have existed for a long time within the RATP signage policy and that, modernized, provoke immediate user reflexes. (RATP 1997: 2) Specific features of subway signs, such as materials and colors, are designed to support this reactive attitude. Some of them are generally inherited from a longer history than subway systems themselves. It is the case of certain colors, or shapes, that are used to operate a real ʻsemiotization' of the signboards. B. [START_REF] Fraenkel | Actes écrits, actes oraux: la performativité à l'épreuve de l'écriture[END_REF] constituted this kind of conventional work as a key issue of her theory of writing acts: some actions can be fully inscribed in the material support. Here, colors and shapes support the differentiation between the boards and the identification of the distinct functions that are attributed to them. Such a semiotic investment relies on a standardization process. In order to accompany reactive movements, colors and shapes have to remain strictly the same all over the subway network. Because they perform a strongly ordered setting, they are key components of the stabilization of the space itself.

To become a reactive entity, the rider has to adopt an almost animalistic attitude within this stabilized surrounding. She has to restrict her way finding operations to sheer ʻperceptive procedures' (Hutchins 1995b). By walking on corridors or platforms, she has to identify signs at first glance and at a great distance. For example, she can easily follow the ʻexit' boards thanks to their glossy dark blue in Paris. In a way, she has to stop thinking and to use only her eyes, in order to delegate the control of her ride to the artifacts installed in the surroundings. In the course of our rides, we regularly adopted this reactive position, notably when we followed the color of the relevant line for the next connection. We only had to glimpse the color while moving and mainly focusing our attention on one of our stimulating theoretical debates.

In such a framework of action, each sign has to be grasped as a clue to go on and movement is performed in a series of perception/action sequences.

During the whole trip, signage should be followed as the best of guides. Signs take over one from another; one has simply to follow them in order to get to the city and to reach closer to her destination. (RATP, 1997: 2)

Thus, the rider must be able to engage in a step-by-step process, following one lower-level instruction after another, what the designers called an ʻAriadne's thread' (Wiart, Le Roux and Lomazzi 1998).

This form of engagement between the rider and her environment is close to what C. [START_REF] Bessy | Experts et faussaires : pour une sociologie de la perception[END_REF] termed the ʻrégime d'emprise', where people and things are tightly bounded, which cancels any human pretension to objectivization. To become a reactive entity, the rider has to accept this dependency to the surroundings. She then reaches a particular state that ʻis characterized by the absence of rupture between entities [… and] leads to the impossibility of any kind of detachment' (Bessy and Chateauraynaud 1995: 263).

What is performed here is the seamless circulation of bodies through the network. The riders are configured as entities moved by the fluidity of traffic. From this point of view, the script is pretty different from the previous one where people are supposed to stop at each junction, even briefly, and make choices between options clearly exposed by the signage components. Even if both scripts involve a similar process of delegation to the environment, they perform two distinct rhythms of movement.

Conclusion

What have we learned from the details of Parisian signage scripts and from the analysis of the embodied practices they require? Above all, we showed that the accountability performed by subway signs is plural. We identified four different figures of riders: the informed one, who wants to control her trip and has to read messages; the planner, who anticipates the conditions of her ride and has to use calculation devices; the problem solver, who calms down her anxiety by finding clear options exposed on recognizable signboards; the reactive entity, who circulates smoothly by responding automatically to specific graphical features of the surroundings.

In the Parisian subway spaces, the rider is never performed only as a reader who would catch some meaning from various texts. Sometimes she is more ʻactive' (when she has to compute data to plan her trip), and sometimes more ʻpassive' (when she has to react automatically after perceiving the shape or the color of a signboard). Signage displays neither a text, nor a discourse. It is made of the ʻa-signifying elements of time, space, rhythm, movement, bodies and so on' (Fuller 2002: 241).

Such a plurality strongly contrasts with the metaphor of reading that still has great resonance in the analysis of urban settings and where streets, squares, buildings, and cities themselves are supposed to be legible [START_REF] Stierle | La Capitale des signes[END_REF]. This metaphor invites to study cities as texts and implicitly promotes a literate accountability. In contrast, we saw that designers strive to fit out a graphical accountability that relies on a wide range of actions.

Interestingly, in designers' discourses, the riders' figures are never reduced to ʻtypes' of riders or marketing targets. They neither mobilize ontological definitions of individual users, nor pretend to describe any kind of diversity within the population. The pluralistic accountability that the signage provides concerns each single rider. The same person may go throughout various frameworks in the course of a single trip. Generally, she actually has to do so.

Thanks to signage, plurality is a feature of the surroundings. However, it does not mean that every figure is supported anytime and everywhere. Precisely, the graphical ordering aimed to support the ʻsuccess' of rides is performed by the spatial and temporal distribution of the signs, and the riders' states they are intended to generate. Subway spaces are designed as pathways where the available resources for orientation change according to the section one goes through. Successful rides should be performed by the successive encounters between the riders' adequate states and the standardized signboards, that is, the progressive actualization of different scripts.

That is how the signage performs a public space: it ascribes states and positions to people according to the sites they cross. Such a performation process accomplishes a configuration, that is, an articulation between particular figurations of spaces and certain figures of riders. But while the first ones are in the hand of the designers and the placement workers (Denis and Pontille forthcoming), the second ones remain virtual. To be actualized, they have to be enacted on the spot by disciplined riders who, as the pedestrian in Paris described by [START_REF] Latour | Paris ville invisible[END_REF], go through one device to another, through one user's figure to another:

I'm not simply passing through Paris: the ʻI' also passes through forms of action, regimes of intelligence that are virtually unrelated to one another.

[…] From one second to the next different regimes of action relayed one another, leading me from one competence to the next. I'm neither in control nor without control: I'm formatted. I'm afforded possibilities for my existence, based on teeming devices scattered throughout the city. I go from one offer to the next. To progress a little further I grasp the small bit of program that others have stuck onto each device for me. (Latour and Hermant 1998, p. 68) But, unlike to the various devices present in the streets that address different senses (hearing, sight, touch…), the signage confronts the riders to a sole kind of artifacts. Its plurality remains within the world of signs, and the regimes of action that it supposes are always a matter of gazes and visibility. In other terms, the graphical accountability provided by signage inscribes a politics of attention in public settings.

E. [START_REF] Goffman | The Presentation of Self in Everyday Life[END_REF] insisted on the human side of public spaces. He showed the importance of ʻcivil inattention' that occurs within cities, that is, the ability of people to be aware of others without conspicuously focusing on their movements and attitudes. The case of signage shows that non-humans can also become a crucial matter of concern in the organizing of public settings (Latour 2005a). To properly use the Parisian subway system, the riders have to be aware of numerous graphical artifacts. Dwelling in subway spaces requires, besides a civil attention, a graphic attention, which, as we showed, demands several specific cognitive skills. And not only have the riders to dispose of these skills: they also need to juggle with them, from one site to another, from one moment to another.

This politics of attention rests on the designers' desire to build an omnipresent graphical apparatus, meant to encompass all kinds of uses. Largely inspired by social theories that took part in Design Research and Human Computer Interaction Studies (such as ʻsituated action' and ʻdistributed cognition'), it performs a user-centric world. It is then highly individualistic. Even if signage is a form of public lettering, devoted to several people in the same time [START_REF] Petrucci | Public Lettering. Script, Power, and Culture[END_REF], it actually provides an interface that each isolated person can use to navigate the world. The four scripts of the Parisian subway signs, which inscribe various ways to distribute some features of the human cognition within the surroundings, all require a ʻface-to-face' relationship between a rider and the signage components. They clearly rely on an individual cognitive availability. In other terms, the Parisian signage is meant to equip a rider who could be all alone. By following the sole signboards directions she could still manage to find her way within the transportation network.

The Parisian signage thus performs a very specific public setting. In order to more precisely understand it, one can ask one of the favorite questions of the Actor-Network Theory: what is delegated in this artifact? We saw that signage is not representational. It then has nothing to do with the public display of matters of concern, that is, things we collectively consider (Latour 2005a). Actually, the signage operates a twofold delegation. Signs are meant to replace and, above all, expand the presence of employees of the carrier who could verbally help the riders. But they also replace the collective of co-present riders. From the designers' view, the fact that a rider asks for her way to another rider is considered as a failure. What is at stake with the omnipresence and the standardization of signboards is not public consciousness, but strictly personal guidance. It seems that this kind of individual gears are currently growing, with the success of numerous Global Positioning System (GPS) devices on the one hand and real-time information urban displays on the other. This twofold equipment, of people and places, perform public settings that are augmented with an informational layer, a whole interface, and that are evaluated in the sole terms of operability and efficiency. It sets the basis for public spaces where dwelling together counts less than successfully navigating side by side.

Primary sources

  RATP 1993, Politique de l'information des voyageurs. Point sur la mise en oeuvre, Annexe au Conseil d'Administration du 29 Octobre 1993. RATP 1997, Signalétique multimodale. La RATP fait signe aux voyageurs, Document de présentation interne, Département des projets, Conception de l'information. RATP 2002, La signalétique multimodale. Code des espaces voyageurs, Document de présentation interne. Wiart, A., Le Roux, A. and Lomazzi, M. 1998, 'Signalétique, le nouveau fil d'Ariane', La vie du rail et des transports, no. 57, pp. 30-5.

* This research is part of a collective project entitled ʻEcologies and Politics of Writing' (and supported by the Agence Nationale de la Recherche, Grant n°ANR-05-BLAN-0272-02. We gratefully acknowledge the people from the Régie Autonome des Transports Parisiens (RATP) for their active cooperation and the time they devoted to this study.