" New road investment in congested urban areas ultimately reduces speeds on both the roads and the public transport system ". This conclusion coming from the work of a British researcher (M.J.H. MOGRIDGE) can be redefined. It can be used to test if the creation of an attractive public transport subsystem can provide an answer to the congestion problem in urban areas. This article aims to focus on this question, and puts it in an analytic framework. We provide a global approach, addressed specifically to the case of the agglomeration of Lyon.
Although time is easy to measure, some accessibility indicators are more complex, producing different results. Therefore, choosing which indicators to use can be difficult. The NOD software has been developed for optimizing transport studies in planning. Based on properties of transport graph, several accessibility indicators can be used and combined in this program for evaluating transport impacts on time and on space. Two indicators that can be generated simultaneously by NOD are presented in this article: the 'indicateur de circuité' that measures routes with constrained roads and the indicator that measures optimal routes. Three examples of simulation are presented (autoroutes A20 Vierzon/Toulouse, A51 Grenoble/Sisteron, A75 Clermont-Ferrand/Beziers) and which illustrate that sometimes 'good effects' are not as good as they seem to be with a 'basic' accessibility indicator...
The fragmentation of the urban patterns is actually a largely discussed topic in urban planning. In particular the consumption of space and the traffic flows generated are considered as most negative impacts of this development. However, for many reasons it doesn’t seem possible to find simple solutions to manage this evolution. The mobility has changed the way of life of the agents and the experience shows that planning concepts, which don’t tend to take into account such desires, risk to fail. In the present paper we focus on the question if alternative geometric concepts, based on fractal geometry, provide an instrument to reflect about spatial patterns which allow to respect simultaneously different desires of agents. In a first part we tackle with different concepts of urbanism under sociological and spatial aspects. Then the use of fractal geometry in such a conceptual context is considered, taking into account the aspect of the accessibility of different functions and different approaches are discussed which allow to measure the quality of accessibility of transportation networks.
The paper provides a review of urban travel demand models development paralleled with changes in the planning context. In particular, the principles, contributions and limits of the integrated land use and transport models are introduced. These models represent tools which allow long term effects of strategic planning policies to be simulated, taking interactions between the transport and the land use into account. These models derive from urban economics and transport economics. An evaluation of these tools is presented. It is based on both a comparative study led by United Kingdom Transport and Road Research Laboratory in the 80’s, and on the criteria of operative efficiency of a model developed by Bonnafous.
The question of the impact of heavy transport infrastructures still remains a tremendous scientific enigma. They are few certainties about this problem at the moment, while a real political mystification of the effects of big amenities, known as "structuring infrastructures" develop outside the scientific community. But recent theoretical progress in geography and in regional economics, confirmed by extensive case studies, allows the investigation of new conceptual tracks to attempt to identify and understand the way these big infrastructures influence spatial structures and dynamics. Our research team gives greater importance to the study of the processes by which a transport infrastructure influences a spatial system. Among these, the one we call "process of usefulness and use" is essential. As one considers that the infrastructure provides new transport possibilities, we need to identify and then understand the way individuals and economics actors use them. This approach is applied to observe the economic effects of the A39 motorway (east of France).
As their development gets stronger, the influence of IT on location of activities gets weaker : this effect will be called the "paradox of location". But the role of IT is essential in the setting up of a new spatial organisation of production, according to a network scheme, where the connection between functions and between firms is more important than their physical vicinity. The territory of flows restructures the territory of places.
Regional railways passenger transport is experiencing today a new expansion. This revival is based on new developments in the economic theory of fiscal federalism, dealing with decentralization mechanisms and efficiency of public activities in a multi-level government structure. Regionalization can then appear as an adapted answer to today’s issue of monopolistic regulation of railways transport. German experiences are, from this point of view, interesting because they show, unlike the British choices, an integration and a modernization of railways activities in a bottom up approach. They thus aim at transparency, controlled opening to competition and a reorganization of public transports institutions around co-operative choices. On the contrary, French choices are made more cautiously, by testing out in six Regions a transfer of competencies from the S.N.C.F. and the State to the Regions. But by refusing to investigate institutional issues such as the monopoly of the S.N.C.F. and the institutional splitting up of the transport competency, the French test on regionalization appears more like an attempt in dealing with scarcity than an effort towards optimizing.