Scholarly article on topic 'Towards a Sustainable Development Approach in Transport Assessment'

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Abstract of research paper on Civil engineering, author of scientific article — David Meunier

Abstract Transport project assessment, starting from a classical socio-economic approach using cost benefit analysis, has progressively taken into account environmental concerns, both through external cost estimates used in socio-economic indicators and through environmental studies, which havebecome compulsory in many countries as is the case in the European Union. The purpose of this paper is to analyse in what directions the transport assessment system could go in order to be more in line with a sustainable development (SD) approach. After a discussion on selected key characteristics of SD as guides for the analysis, we analyse the existing situation and its current developments as illustrated by a French case, and try to see what would be missing with regard to the key characteristics identified. Finally, ideas for a new approach in project assessment are discussed, covering the assessment process, its contents, and its links with project design, from a SD point of view.

Academic research paper on topic "Towards a Sustainable Development Approach in Transport Assessment"

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Procedia - Social and Behavioral Sciences 48 (2012) 3065 - 3077

Transport Research Arena- Europe 2012

Towards a sustainable development approach in transport assessment

David Meunier1*

°Université Paris-Est, LMT, UMR T940S Ecoles des Ponts ParisTechIFSTTAR UPEMLV

Abstract

Transport project assessment, starting from a classical socio-economic approach using cost benefit analysis, has progressively taken into account environmental concerns, both through external cost estimates used in socio-economic indicators and through environmental studies, which have become compulsory in many countries as is the case in the European Union.

The purpose of this paper is to analyse in what directions the transport assessment system could go in order to be more in line with a sustainable development (SD) approach. After a discussion on selected key characteristics of SD as guides for the analysis, we analyse the existing situation and its current developments as illustrated by a French case, and try to see what would be missing with regard to the key characteristics identified.

Finally, ideas for a new approach in project assessment are discussed, covering the assessment process, its contents, and its links with project design, from a SD point of view.

© 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of the Programme Committee of the Transport Research Arena 2012

Sustainable development, evaluation, assessment process, transport project, governance, impact study

1. Introduction

Transport infrastructure has for a long time been one of the few fields where public project assessment has been intensively put in practice. Historically starting from a classical socio-economic approach using cost benefit analysis, transport assessment has progressively taken into account environmental concerns. This has been obtained both through external cost estimates used in socio-economic indicators and

* E-mail address-, david.meunier@enpc.fr

1877-0428 © 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of the Programme Committee of the Transport Research Arena 2012

doi:10.1016/j.sbspro.2012.06.1273

through environmental studies, which have become compulsory in many countries as is the case in the European Union.

Still, though they now have some intersections, cost-benefit analysis (CBA) and environmental assessment are mostly developed in parallel. Other kinds of assessment (financial analysis, multi-criteria analysis) cast some light on some complementary issues; but social aspects and other sustainable development (SD) topics such as risks and uncertainties, or project governance, are often not considered specifically, even though some countries have developed methodological frameworks to cope with some these topics. The purpose of this paper is to analyse in what directions the transport assessment system could go in order to be more in line with a sustainable development (SD) approach. After a discussion on selected key characteristics of SD as guides for the analysis, we analyse the existing situation and its current developments as illustrated by a French case, and try to see what would be missing with regard to the key characteristics identified. We will focus on big infrastructure projects. The principle of proportionality leads to adjust the assessment effort to the size of the projects; in a SD approach, though, the size of the project is not only a question of physical size or construction costs, it includes the potential magnitude of economic, social or environmental impacts.

The reader may have heard of initiatives aiming at obtaining a sustainability index or other kinds of sustainability estimation. Most of them are technical and focussed on methods for combining and aggregating indicators from the 3 pillars. We will not discuss them here since our purpose is at the scale of the transport assessment system; but in the view developed here, even if they were perfect, they would cover only a part of the SD issues. Other initiatives have a broader scope, such as sustainability impact assessment (SIA) processes, promoted by OECD (OECD 2010) or the European Union. These initiatives focus in fact mainly on regulatory issues (RIA) and are policy-oriented. Again, our purpose is not the same, SIAs give a general framework for policy-makers, whereas here we focus on the transport assessment system and start from the existing system rather than trying to build from scratch.

To begin with, we could try to start from the definition of "sustainable development". Unfortunately, it has many meanings (Williams § Millington, 2004), and even the well-known Bruntland definition (United Nations, 1987) is sometimes given several interpretations. Therefore we will not go into deep discussion in order to choose between "weak" or "strong" SD nor discuss the difference between green growth or green economy or question mixed concepts such as environmental sustainability (Ekins, 1999). Instead, the focus will be put on some main characteristics of what could be called the SD philosophy.

First of all, the unavoidable three pillars of SD may be interpreted for transport assessment as estimation of economic, environmental and social impacts, through diverse criteria and indicators. But besides this basic approach, we will retain as key issues of SDt the time dimension - not limited to taking account of next generations -, the issue of governance - which is linked to the social dimension but goes far beyond -, and the issue of uncertainty which is present in many different forms. But furthermore, sustainable development implies also not only observation and analysis. It is also a philosophy of action. This last characteristic is somewhat difficult to cope with for transport assessment, since assessment exercises do focus on organized data gathering, interpretation with the help of methodologies, and presentation of results. There seems to be no room for action, since assessment stops where decision begins, the main challenge being to give to decision-makers the most adequate processed information on the consequences of their possible decisions. We will see that, while retaining the clear limit between assessment and decision, the SD philosophy of action can be transposed to transport assessment.

+ Some authors (see Gibson 2006) go much further and propose to design sustainability assessment as a fully integrative process and accordingly to redefine evaluation criteria which would avoid the three conventional pillars. We propose here a medium way, because our starting point is the existing transport assessment system, because we feel that this system can evolve on the key SD issues selected, and because progress on these issues appears to be a pre-requisite on the way to ideal SD assessment.

2. Sustainable development concerns and transport evaluation

2.1. Thethreepillars

Let us begin with a first rapid overview of the most well-known characteristic of SD, the "three pillars issue". In transport assessment, the economic pillar was the first one to be treated, with the development of CBA methods1. Thus, both data sources and methodologies have available to take care of the economic dimension, at least for conventional economic questions addressed to transport assessment. CBA and financial assessment are dedicated to the economic pillar, even though CBA has enlarged its scope so as to capture in monetised terms some of the environmental (or, rarely, social) impacts. Both need, at least, the results of the traffic studies and monetary information extracted from the project (especially construction and operation costs).

The environmental pillar appeared more precisely in the field of assessment in the seventies and eighties, with legal obligations to produce environmental impact assessments. The official recognition of these pillars may be measured through the existence and extent of the legislative obligations to perform assessment studies. In France, the « LOTI » law in 1982 introduced such an obligation of economic and social assessment for big transport infrastructure projects, but CBA was already used for major transport projects more than 20 years before. Environmental impact assessment was mandatory from a law issued in 1974, more than 10 years before the EU directive 1985/337. More recent environmental obligations have appeared (e.g. directive 2001/42) that aimed toward a larger scope and systematic application, whereas CBA stays obligatory only for at the project level on national bases, for « big projects" even though the practice and regulatory obligations for State projects have much enlarged the scope of these projects. Many countries have this type of obligation in their national law, and in the other countries, the need to get international financing (from European Investment Bank, World Bank, European Commission,...) leads in practice to similar assessment obligations imposed by the international financing bodies. The Aarhus convention is another international obligation applicable to all countries that endorsed the convention. It imposes transparency and public participation principles for environmental studies; this is one of the reasons why European directives impose that environmental studies' results be communicated to the public. EIA is dedicated to the environmental pillar; it relies on more technical studies such as biodiversity data gathering, noise measures and modelling, but also needs as input the results of traffic studies and other technical studies (project alignment, sometimes also geologic studies).

The social pillar was for a long time considered at the scale of the collective entity concerned (country level for a State): think about such terms as "social surplus" which indicate that the concern was focussed on the overall impact. But the evolution of societies has given more and more importance to individuals, and the driving force of equity concerns has led to give a completely different meaning to the social pillar, focussing it on distributional effects or attention given to the worse off - poorer, more isolated, ...(explored more in depth in many works, such as the Stiglitz-Sen-Fitoussi report, 2009). For a long time, project assessment could write down in the "social impacts" column not much more than the project's impact onjobs, and the impacts on safety, because it was not asked more. No specific assessment analysis is dedicated to the social pillar. It would need detailed information on the distribution (in terms of geography, population group, income level, economic actors,....) of many parameters, indeed of main technical, economic and environmental impacts (for instance, distribution of the degree of exposure to noise, of the final share in construction costs, of time savings).

* for a more detailed presentation of CBA evolution, the reader may see Quinet,/Meunier (2012).

This rapid overview, and the present contents of transport assessment studies, indicates that assessment in the transport field is not an exception5: among the 3 pillars, the social one is here also the less developed. It would deserve much effort to reach the other 2 pillars' level in terms of data gathering and methodologies.

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Figure 1: Transport Infrastructure Assessment (Present)

2.2. Other key characteristics ofsustainable development

We will now review other key characteristics of SD, in relation to the main types of assessment analyses which are usually produced for big transport investments.

2.2.1. Time and geographic scales

The time dimension is essential for transport assessment, due to the long lifetime of infrastructures. In CBA, the assessment period is about 30 to 50 years, sometimes more, and discounting is used for representing trade-offs along the time dimension. Environmental studies take account of the time dimension rather as a comparison between "before" and "after" project implementation for direct construction impacts, and deals with cumulative impacts when the infrastructure is in operation, there is no discounting of cumulative impacts over time, but account is sometimes taken of natural reaction cycles that may absorb or on the contrary amplify the infrastructure's impacts. The surge of life-cycle analysis is an interesting evolution which aims at encompassing the time dimension at the level of physical products. It may enrich assessment with more pertinent costs and environmental (possibly social, too) impacts. Also, both environmental assessment and advanced CBA consider mid and long term impacts linking transportation issues with other issues such as land use or GDP. All this increases the need for new dynamic modelling tools that would be able to represent complex interactions. The surge of LUTI or SGCE models may be seen as preliminary answers to these growing needs. In the assessment process

5 See for instance Lehtonen (2004).

itself, the time dimension appears in CBA only through the identification of key stages of the project where CBA is required (there are usually one or two such steps, plus, rarely, an ex-post evaluation) but environmental studies do also integrate the time dimension in relation to a feed-back process on project design (we will come back to this in part 2.2.4.).

The geographical dimension is key for getting a comprehensive view that is required for SD assessment. Environmental assessment does integrate such a dimension in its techniques (ex: ratio of valuable natural surfaces impacted, scarcity of species at diverse geographic scales), but usual CBA does not pay interest to geography, since monetary flows are equivalent wherever they are observed. The only mention of geographical scale is, rarely, when CBA is performed at diverse geographical scales (eg regional, national, European union). Whether for CBA or environmental assessment, an SD approach would lead to pay attention to combined impacts, i.e. to perform transport assessment not only at the project's level but also at a higher level when several projects (transport projects or other) may interfere. Such a need for upper-level assessment could derive from diverse approaches: functional (infrastructure programme or plan), geographical (territorial level), ecological, economical or social. Indeed, for all kinds of aggregation, the projects' impacts may combine in a non-additive way (network effects, synergies, cumulated effects on eco-systems, ...) and this kind of phenomenon is important in a SD view."

The geographic and time dimensions may also be considered as axes for distributive analyses, as social or economic axes may be used (low income population, small and medium firms, ...). They cover not only economy but all the 3 SD pillars. Thus, even if usual assessment analyses have to evolve as regards these SD characteristics, the need appears for transverse analyses, such as trans-generational analyses covering all 3 pillars. Also, the distributive issues increase the need for more diversified and more precise (disaggregated) databases and GIS.

2.2.2. Governance

Even though the governance issue may seem to be ignored by conventional CBA, there remains an influence of the evolution of project governance. This leads CBA, would it be only through its participation in public debates on the project, to exchange information with stakeholders (the CBA analyst can hardly stay always in his office). Besides, the development of co-financing schemes also led to use economic information in the dialogue between financing partnerstt. As another result of project governance's evolution, specific economic questions are increasingly being addressed to economic analysis in answer to issues stemming from public debates.

Opposite to CBA, environmental assessment is the assessment analysis which has most included governance in its concerns, one could even say in its genes, both with public communication rules and with the "avoid, reduce, remedy/compensate" logics that we will talk more about later.

Multi-Criteria Analysis (MCA) methods are also applied by some authorities, and the MCA approach is gaining audience also for big projects, mainly for the reason that it may help to understand stakeholders' attitudes and to discuss with them. It is then used as a help for project governance. But it may interfere with local governance, especially when MCA results go beyond a comprehensive presentation of the project's impacts, and reduce the multidimensional information they convey to a

Anyone may think, for instance, of underpriviledged suburbs which have progressively been disfigured and cut by several motorways, rail links or polluting plants.

+t For instance, analyses of the repartition of user surplus among regions or local territories have been used for the discussions on recent high speed lines' financing schemes

single indicator, whatever this composite indicator be. Then, the "black-box" syndrome may cause governance problems^.

Still, all these three types of analyses, even if they interact with the project's governance, do not consider it as an object of their screening.

2.2.3. Risks and uncertainty

Increased perception of risks in the economic field has led financial analysis, and also CBA, to pay more attention to risk and uncertainty. As public-private schemes appeared, and co-financing schemes with multiple partners developed, the need for a correct representation of consequences of contracts /risk sharing rules became stronger.

And ex post studies show clearly that risk sources are very varied: not only usual economic factors (GDP growth, petrol prices,..) but also environmental ones (knowledge on the presence or scarcity of rare species, on pollution sources). Social risks usually refer more to acceptability risks (potential social unbalances reveal only in special conditions, but evaluation should help in detecting the level of risk ex ante, not only observing its occurrence ex post. And risks originating in one dimension may transfer into another: typically, environmental risks can transfer to acceptability risks and then to economic or financial risks. A good example here is the TEO highway project in Lyon: in order to reduce financial risks, pricing and network management measures where taken that caused great unbalances in the repartition of surpluses, causing very strong opposition and a collapse of the initial financing and organizational scheme (see Raux § Souche 2004). More often, environmental impacts caused such tensions and demonstrations that projects were simply abandoned.

Going further, in the long term view of SD, we should also pay attention to the uncertainty on future generations' needs. Take for instance the dramatic change in social preferences as regards tunnel safety in Europe and especially France after the great accident of Mont-Blanc tunnel 13 years ago. Some evolutions are more progressive: issues such as noise have become very important now, while they were not considered 40 years ago.

2.2.4. Assessment and action in SD approaches

Last, let us turn to the often forgotten characteristic of SD, its "philosophy of action". Indeed, it already appears in some of the present assessment studies, mainly in environmental impact studies: their logics of "avoid, reduce, compensate" is clearly intended to interact with project's design at specific stages in the project's life, there is really a philosophy of action underneath. Avoidance is easier in early stages of the project (especially as regards choices in project alignment), reduction is intermediary and compensation is to be used as a last solution, and, when needed, it is indeed defined precisely when the project is very mature and about to be implemented.

There is no such philosophy of action in other assessment studies, except perhaps through the belief or hope that CBA (or MCA) results bear a "rational and objective value" that should guide or at least influence public action. But even if we go this far, the action in question is limited to punctual choices: build the project or not, choose such or such variant.

In fact, the SD "philosophy of action" should induce transport assessment to become more interactive with project's design and governance, i.e. to help in improving the projects not only on environmental terms as EIA does already, but also on the other SD dimensions. A closer interaction between assessment

** Aggregating methods such as environmental footprint may be assimilated to MCA. They are subject to the same critics, and so could be some sustainability assessment approaches which focus on measuring a "sustainability note" through sustainability indicators, or on determining whether the project is sustainable or not (Pope § al 2004).

and project design would also imply a greater use of analytic tools such as value analysis. Incidentally, such an evolution would require new competencies to be developed together with a parallel update of project governance, management rules, and project assessment organization.

Another angle of "philosophy of action" may be discussed: the implicit optimization logics of existing assessment methods may be considered in this view. Indeed, conventional CBA aims at maximising a measure of aggregated surplus based on monetary exchanges and monetisation. Conventional environmental assessment aims at minimizing negative impacts on the present state of nature and human health. Contrastingly, a sustainable approach to assessment would aim at estimating the impacts of balance changes (balance shifts or break-points) in a complex dynamic system, with an understanding of risks and therefore of the imperfect clarity and precision of its own representation. The issue is not anymore mono-thematic optimization, but a search for paths where the main balances of the dynamic system would be more likely to be maintained or strengthened for a long time. For the moment, we seem to be in an intermediary stage where some thematic methodologies have been developed in order to represent complex dynamic systems, such as the DPSIR causal framework promoted by the European Environment Agency and recent developments on indicators (e.g. COST 356, 2010).

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3. The example of the French national transportation infrastructure plan (SNIT)

In France, the ministries for transport, environment and sustainable development where united a few years ago, creating new conditions for developing SD assessment in a more integrated way. The environmental summit « Grenelle de l'environnement » (2007) held a great importance in France and led

to numerous decisions intended to make the whole society move towards more environment friendly ways of thinking and acting, and more generally towards sustainable development. A National transportation infrastructure scheme, the SNIT, is currently being prepared, whose assessment is presented, describing the innovative process that has been used, the interest and the present limits of this integrated assessment. The SNIT has been given by law several objectives that go well beyond the usual functional objectives of infrastructure networks, and include for instance contribution to greenhouse gases emission reduction, The SNIT does not reduce to an infrastructure long term planning document. It gives the orientations and lists about 50 innovative actions concerning the national policies on maintenance, renewal and operation of national networks, and national contribution to urban transit development. It covers all modes including intermodal transportation (e.g. motorways of the sea).

First of all, since the SNIT is a national planning document, the decision was rapidly taken to apply directive 2001/42 (European Union, 2001), i.e. to produce an environmental assessment report complying with strict rules. It was also decided to produce a general assessment of the Plan, covering all dimensions of sustainable development, within the limits of available data and degree of precision of the decisions included into the SNIT. For the SNIT's infrastructure planning dimension, both assessments estimated the SNIT's impacts relatively to a reference network and to an alternative infrastructure plan issued in 2003. Both assessment reports have been made public for general discussion with the CNDDGE (the National Committee for SD), stakeholders, the public; and an amended version of the SNIT will have to be examined by the French Parliament. We will concentrate on the overall assessment of the SNIT, since its environmental assessment follows the clearly defined lines of the directive, whereas the overall assessment was due to be fully innovative.

Some aspects of this new assessment process are presented below, screened through the SD key characteristics already mentioned. In comparison with usual assessment processes, innovative aspects included the following:

• narrow coordination of various specialists within a project-team aiming at a common goal, developing common methodologies and consistent assumptions

• concrete interaction with project design, although rather limited for this first experience

• governance has been treated as an object of analysis, an overall SD assessment has been produced and made public - on the Web - , feeding the discussion on the national plan contents

• the analytical concern about geographical scales produced new information on regional distribution and on biodiversity risks

• transverse risk analysis has been limited for this first exercise, but key points on which vigilance will be required have been identified, that could induce important economic, social and/or environmental consequences.

3.1. Overall assessment ofthe SNIT

For this first experience of integrated assessment, some methodological innovations have been tested, but with regard to the high expectations for SD assessment mentioned above, strong limits were encountered, that concerned the whole assessment system on various topics such as methodologies, data collection, problems of temporal or geographical scale, or the degree of maturity of infrastructure projects. Among the difficulties encountered, the infrastructure projects were at highly diverse stages of maturity, some where highly advanced and known in high detail, many others were at very preliminary stages. This problem was more acute for environmental assessment, which requires localized information. We do not have room here for presenting the economic, social and environmental impacts estimated by the SNIT's overall assessment (see CGDD, 2001). The focus will be put on the transversal characteristics of SD assessment presented in the previous section.

An interesting feature is that design and assessment of the SNIT were developed in parallel. This made possible, on some occasions, some feedback from evaluation to design, and the assessment exercise showed clearly that a continuous monitoring-evaluation process was needed at the stage of SNIT implementation. Such a process would highly facilitate the interactions between implementation of SNIT and evaluation, and will also help to improve preparation of future revisions of SNIT. This is a way for implementing the "SD philosophy of action".

Environmental impact assessment, traffic modelling and overall assessment were made in parallel, but with regular contacts and exchange of information and coordination of hypotheses, for consistency and quality motives. This type of coordination between studies helped to enrich the whole process. Considering the time dimension, since the SNIT is purely a planning exercise, its assessment was not used for setting chronological priorities ; but it highlighted warning points and the need for ulterior focussed assessment analyses to be made, at the implementation stage of the SNIT. The transfers between generations appeared when analysing the SNIT's orientation "switch from curative to preventive maintenance", which needs additional short term financing. Another example in time dimension approach is the tentative estimation of GHG emissions at the stage of infrastructure construction, whereas most present assessment exercises do only consider the traffic emissions.

The geographic dimension was considered for traffic estimation, environmental assessment and distributive analysis (the question of macro-economic impacts was examined but considered not to be conclusive due to the divergence observed in estimation results). The use of a national model helped to capture network effects and transfer from or to neighbour countries' networks. The environmental assessment made a great use of GIS which helped, for instance, to highlight potential risks on some specific species, due to the expected aggregated location of planned infrastructures, e.g. birds species such as the little bustard. Since a good part of the infrastructure projects is at an early stage with very imprecise alignment, most elements of the environmental assessment where to be taken as "potential impacts". The actual impacts will depend partly on exogenous factors and, for a good part, on the optimization efforts in ulterior project design. In a sense, this analysis helped to highlight important risks with which the SNIT will be confronted at implementation stage. Distributive analysis using household or firm typology was not possible for this first SNIT overall assessment, for many technical reasons, but a regional distribution analysis was performed as regards accessibility gains. Governance was one of the issues of the assessment exercise. Indeed, the existence of the SNIT results from the "Grenelle law" that was issued after the national environment summit "Grenelle de l'environnement". A specific and innovative governance was used for this roundtable, that led to the creation of the CNDDGE (General committee for sustainable development and the Grenelle of environment). This committee includes representatives from the State, from elected politicians, firms representatives, unions, and nongovernmental associations, and the CNDDGE was associated to the SNIT's elaboration. As for the SNIT's assessment itself, its process and results where subject to exchanges with a technical group derived from the CNDDGE.

Due to the complex nature of the SNIT, internal consistency checks were performed together with external checks, i.e. consistency with transport and other public policies. This helped also to shed light on assessment issues to be treated at the implementation stage. Incidentally, both consistency checks at the project level and the need for combined projects' impact estimation should lead transport assessment to interact more with methodologies and analytic studies of other fields (territorial planning, urbanism,...).

The topic of risk and uncertainty was only partially covered, mainly concerning the technical uncertainties. The latter were numerous, and concerned all analyses (traffic, CBA, environment), thus the aim was not to obtain very precise figures but rather orders of magnitude of potential impacts. When possible, different methodologies were used and their results compared. This helped to gain confidence in the robustness of the analyses. For instance, traffic shifts from one mode to another, which are important for the French transport policy and are in the same time major elements for GHG emissions, were

estimated using a multimodal model at the national scale, and compared to the aggregate results from individual projects' traffic studies. Even if additivity conditions were not met from a theoretical point of view, the same order of magnitude was obtained. Some sensitivity tests were also performed.

Uncertainties did appear differently for the diverse analyses. For impacts on natural land, the main difficulty was that most projects do no yet have a precise alignment. Thus technical uncertainty was very high, and the usual indicator of natural surface reduction due to the projects could not be used as such: it was only possible to speak of potential impact on natural areas. For common natural areas, as long as the territories crossed by the project are not too heterogeneous, the order of magnitude should be robust. But for exceptional areas, the risk level depends on technical constraints but also on the attitude of the project's manager. Some risks emerged from the analyses, which are common to several dimensions. For instance, the reference speed of HST lines may impact their competitive position and thus their traffic level, their economic and financial performance (higher speed meaning increased attractiveness but higher construction costs). But a higher reference speed means less flexibility in alignment optimization and therefore higher environmental risk (less possibilities to bypass sensible areas, more backfill and land consumption), and possibly social risk (acceptability risks due to reduced alignment optimization with regard to housing location or to zones highly valued). The assessment concluded that project optimization considering these issues was strongly recommended, using analytical tools such as value analysis.

The risk analysis, even though it did not use sophisticated tools nor included a large and systematic review of risks, threw light on a few critical issues that will deserve much attention at the stage of implementation of the national scheme. This is in line with the SD "philosophy of action", and it shows that even at very preliminary stages, SD assessment may be useful for public action improvement, in line with the SD process of risk exploration and management along time, continuous use of additional data and gathering of new knowledge.

For example, the case of HST reference speed would induce to systematically perform value analysis and impact analysis for all lines. Similarly, technical uncertainty on GHG emissions' estimation showed the importance of infrastructure programming in this regard, when time dimension and comprehensive approach are used in assessments. Indeed, the final C02 impact proved to be quite sensitive when taking account of the construction phase, which emits a non negligible proportion of the future emission savings induced by a HST line (indicative order of magnitude: 10% to 30%), and when using unit emissions differentiated in the time dimension, consistently with international and national C02 objectives. Some lessons for SD evaluation can be extracted also as regards the data needed for assessment. For instance, it appeared: that the impacts of the activity of current transport networks was not monitored finely enough and needed a minimal observation system, including an "environmental database" at the scale of smaller network links than those used for traffic studies - sub-division according to environmental issues, such as precise identification of Natura 2000 zone pass-through or vicinity of water catchment areas -. SD assessment induces a high need for GISs' coordinated development and exploitation. These lessons should help the French transport system to integrate SD needs from the data gathering level, which is necessary for making SD-oriented monitoring of transport networks and systems.

3.2. Evolution of the evaluation system for transport projects in France

The cases exposed previously illustrate some of the new questions addressed to assessment analysis of transport infrastructures, and shows examples of complementarity or competition between the diverse kinds of analyses.

Within the general assessment framework given by recent texts (MEEDDAT 2008 a,b), the evaluation system for transport projects in France is beginning a process of review and update of its methodologies and reference values. It will take into account the new concerns and questions discussed earlier, with a

systematic background of sustainability concern. The idea is to work on technical improvements and also on a new assessment process, that would improve coordination and collective work of the various types of assessment analyses and of project design and governance. The ambition is to build a consistent framework that, under the legal constraints, takes the better from the different kinds of evaluations and makes them exchange and enrich each other. The whole cycle of evaluation is to be covered, including systematic ex-post exercises which France has practiced for a long time.

4. Conclusions

We have gathered some elements of answer to the question: in what directions could the transport assessment system go in order to be more in line with a sustainable development (SD) approach? It is now time to summarize them.

The analysis of SD characteristics, which go further than the usual 3 pillars of SD, illustrated by the positive and negative observations made on the SNIT's case, has led us to the following observations:

• surely, there is a need to improve the analysis of impacts that refer to economic, to environmental and more specifically to social aspects where the gap between needs and present tools is the greatest

• the usual assessment analyses may be developed in this direction, as they have begun to do

• other characteristics of SD induce the analyst to ask himself new questions, that go further thanjust enlarging the set of impacts

• part of these new questions may be answered by an adaptation of the existing assessment analyses, by an evolution of databases and geographic information systems and by the development of new modeling tools; but, due to the transversality of the new questions, what is needed is an overall layer of analysis, and probably also new specific transverse assessment analyses dedicated to themes such as

« risks and uncertainties », distributive impacts considering various disaggregation logics such as population categories, economic actors, territories or, maybe, a «trans-generational analysis » covering the 3 pillars

• the organization and management of assessment becomes more complex: it is not anymore sufficient to produce independent studies with a minimal coordination, it needs new governance modes and new competencies to be developed, with increased but cautious communication and interaction with stakeholders

• the interaction between assessment and design of projects, in a SD approach, has to be much closer and permanent: an evolution of project governance is also necessary, intertwined with assessment governance and public and stakeholders' association; this topic is at the interface between production of assessment, project management and policy-making

• a closer interaction between assessment and project design implies also a greater use of analytic tools such as value analysis

• finally, the conventional assessment paradigms should evolve in a SD framework: the issue shifts from mono-thematic optimization in a rather mechanistic representation to a multi-dimensional vision of equilibria in a complex dynamic system submitted to uncertainties; consistency analysis and impact-efficiency measures have to complete usual effectiveness and cost-efficiency measures; and, often, assessment will have to pay attention to the combined effects of a set of projects, grouped according to functional but also territorial, ecological, economical or social logics

• transport assessment will have to interact more with methodologies and analytic studies of other fields (territorial planning, urbanism)

• the nature and deepness of such changes indicate that the evolution of our assessment systems will need a long time, especially as our societies' SD concepts and concrete meanings will evolve in

parallel. But the core issues of SD are already known, it is necessary and possible to begin transforming present assessment systems in this regard.

Acknowledgements

I am indebted to two anonymous referees for their stimulating comments and suggestions.

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