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Communication dans un congrès Année : 2014

How scheduled accessibility can assess tramway effects on city spatial cohesion?

Résumé

Context and problematic In France and in Europe, tramway has become during last decades a major trend in urban policies concerning mobility. Although nowadays the less expensive BHNS is often favoured, tramway is generally considered as a success regarding various topics: it is often seen as a sign of sustainable development policy, as well as a marketing asset for the city where it belongs. Moreover, we can assume that urban renewal and urban projects associated to the tramways are considered as successful. However, can we be sure that tramway provides a better accessibility to urban facilities? Regarding public transit performances, how much tramway improves accessibility and who really takes advantage of it? Above all, does this transport mode promote spatial cohesion in cities? Besides car, is urban transit more equitable? It is known that a new and faster transport service — a good example is high-speed rail — often increases accessibility inequalities. Is it different at urban scale? The aim of this research is to shed some light on such a topic, bringing data for decision support in planning and transport policy. Method Tramways impacts are chiefly assessed by the way of CBA or spatial econometrics indicators, aiming at address the effects on land use or real estate market, specifically prices rise. Another kind of approaches deals with modal shift and compare accessibility by car and by tramway. Yet, disaggregated measures of accessibility by tramway are quite rare, and can possibly be complementary with more classical aggregated indicators, like job accessibility. Indeed, activity-based accessibility calls up potential urban mobility behaviours and schedules (Geurs and Ritsema Van Eck 2001). Assuming that each potential activity belongs to a particular place and time, it is therefore possible to assess the potential offered by public urban transit to achieve these activities. To do so, scheduled graphs allow calculating accurate accessibility measures at every minute of the day, modelling the exhaustive timetables of public transit system in a GIS. In the end, this approach permits to assess accessibility toward strategic activities at relevant hours. Unlike other Time-Geography based approaches, this method does not take into account individual agendas, as main objective is to track the inequalities between neighbourhoods of the city. Similar methods had mainly been used at upper scale (L’Hostis et al. 2004). Study case and data Nice, south eastern France, appears in many ways as a car-dependant city. An assessment which can be attributed to its urban morphology, constrained by the sea and the surrounding hills, and by its history. This can explain why the modern tramway is quite recent (2007), but achieves great success, in terms of number of users as well as the city beautification and quality of life issues. Nevertheless, we know little about the true improvement of accessibility due to the tramway, i.e. where are main accessibility gains and whether city is now more transit-connected or not. Several facilities (concerning education, leisure, cultural activities, business, etc.) are selected and located, in addition with the gathering of exhaustive bus (2006 and 2013) and tramway (2013) timetables. Expected Results The main goal of this work is to propose scheduled accessibility indicators that can bring forward not only the level, but also the disparity of accessibility to urban facilities. Specifically, results should show if the public transit service offered in Nice is more or less equitable before the tramway than after, according to accessibility inequalities. Previous works (Conesa 2012) pointed out scheduled accessibility complexity, and in particular significant daily variability and unanticipated results (improving a trip can damage the corresponding return trip, or the same trip at a different time, according to timetables entanglement and required connections to achieve a trip). Challenge here is therefore to re-aggregate the set of results in order to build relevant yet understandable synthesis that can help decision makers. For instance, the first Nice tramway line could initially have connected a peripheral neighbourhood to downtown but another course was chosen. By showing the consequences of this choice, it is perhaps possible to put forward some helpful elements to the current debate concerning line 2, planned in 2017. Conesa, A. (2012) “TOD and Polycentricity: common goals with different results? Lessons from multilevel accessibility measures in Lille metropolitan area”, Building Urban Future with Transit-Oriented Development, BUFTOD 2012 Conference Proceedings, pp. 183-201 Geurs, K. T. and Ritsema van Eck, J. R. (2001), Accessibility measures: review and applications, RIVM, Bilthoven, 265 p. L’Hostis, A., Menerault, P. and Decoupigny, C (2004) “Assessing spatial planning policy with accessibility indicators: the case of Lille's metropolis scenario“, In M. Beuthe, V. Himanen, A. Reggiani and L. Zamparini (eds.), Transport developments and innovations in an evolving world, Berlin, Springer, pp. 293-312

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Dates et versions

halshs-01196222, version 1 (16-09-2015)

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  • HAL Id : halshs-01196222 , version 1

Citer

Alexis Conesa. How scheduled accessibility can assess tramway effects on city spatial cohesion?: The case of Nice urban tramway. NECTAR Conference 2014 – Accessibility, Accessibility and Policy Making, Network on European Communication and Transport Activities Research (NECTAR), Feb 2014, Seville, Spain. ⟨halshs-01196222⟩
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