In the urban networks, the pedestrian frequency of streets is variable. At an aggregated level, it partially depends on the spatial configuration of the urban network. This concept, called the “natural movement”, is a key-notion in space syntax. It is here investigated by assuming several explanatory factors: metric accessibility, network linearity, route linearity, route continuity. Data obtained from a pedestrian movement survey in the city of Lille (France) were used. The factors were represented by series of theoretical frequencies defined with origin and destination points stemmed from real trips. These theoretical frequencies were compared to the observed pedestrian frequencies. The statistical analysis showed that metric accessibility is the first factor explaining the pedestrian flows distribution (60% of variance). The level of route linearity is just a secondary but significant factor.
The multimodal freight network models are traditionally based on the four stages approach in which generation, distribution, modal split and assignment are seen as separated modules. An alternative approach is to represent the multimodal network by a service network, in which each transport operation (loading, unloading, transhipment...) is represented by a dedicated “virtual link”. In such a network, modal choice and assignment can be combined in a single step. This approach, adopted by several authors and known as “super-networks” or “virtual networks” gives interesting results, but requires dedicated assignment methods, which have to distribute flows from an origin to a particular destination over several alternative routes.It comes out that equilibrium assignment techniques are not appropriate when they are used for long haul trips and when only aggregate data on the demand is available. Indeed, the obtained results appear to be very close to an All-or-Nothing assignment, and don’t lead to a sufficient distribution over alternative routes. This can mainly be explained by the fact that, for inter-city, interregional or international traffic, only a small part of the trips is performed during the peak periods in congested areas. Moreover, the demand data collected for large areas is often only available on an annual basis, making it difficult to estimate what happens at a given period of the day. This paper describes a multi-flow, multimodal assignment […]
The metric of the current roads networks tends intrinsically to favour the efficiency of the routes which have the longer range, what leads to promote urban sprawl and automobile dependence. Indeed this metric ensures to individuals the possibility to travel even further, without necessarily increasing their transportation time in the same proportions. According to this assessment, we introduce a new kind of metric, the “slow metric”, which amounts to invert the current ratios of efficiency between the different types of automobile travels, that’s to say to favour the efficiency of the short range travels. At last, we discuss the ability of the slow metric to be a lever, on the one hand to contend automobile dependence in the roads networks design and, on the other hand, in a more general perspective, to promote territorial functionings based on physical proximity between places of lives, what leads them to be more sustainable.
Most of the transportation networks are not determined by their topology only but also by the traffic taking place on the links. It is therefore crucial to characterize the traffic and its possible correlations with the network’s topology. We first define and introduce some of the tools which allows for the characterization of the traffic and the structure of a weighted network. We illustrate these measures on the example of the airport network in which the nodes are airports and where links represent direct connections. The weight on each link is then given by the number of passengers. The main results are the following: (i) the traffic is very heterogeneous and is distributed according to a broad law; (ii) the number of passengers per connection is not constant and increases with the number of connections of an airport, which implies that traffic and topology are not independent. More generally, these measures show that the traffic cannot in general be ignored and that the modeling of transportation networks has to integrate simultaneously both the topology and the weights. We thus propose a model which allows to explain some of the features observed in real-world networks. The main ingredient in this weighted network growth model is a dynamical coupling between weights and links: every time a new link enters the system, the traffic is perturbed. We show that this simple ingredient allows to understand the structure of some real-world weighted networks as well as the […]
Walking has long been neglected in urban mobility research. In the context of a sustainable mobility, it is now included into numerous works including various approaches. The well-known models of flows affectation are often used to study the behaviour of pedestrians and to identify their preferences. However, the factors that are usually chosen to describe the urban environment are usually limited or inappropriate to the pedestrian movement. In addition, these models assume that the choices made by pedestrians are predetermined at the start of each trip, without any possible decision intervening along these trips. In this paper, we propose to test the role of urban landscape by using a new route choice analysis method. An algorithm is used to find the “junctions”, i.e. the crossroads from which pedestrians chose a route longer than the shortest path. A set of junctions allows us to apply a discrete choice model in order to evaluate the influence of urban landscapes.
The classical theory of the graphs used to describe the networks considers the nodes in a homogeneous way. However the heterogeneity of space implies a variability of the conditions of circulation and thus of the emissions. The algorithmic transformation of an unspecified graph into cellular graph is possible by the theory of graphs. A fine description of an urban network increases the description of the networks to locate urban structure. The creation of a Multi-Agent System simulating displacements of the vehicles on the graph according to rules makes it possible to evaluate not only the constraints imposed by the network but also those imposed by the traffic. The association of the cellular graphs and the SMA allows to precise the localisation of the emissions on the network and to measure the impacts of installations on these last.
The major liner shipping companies are more and more involved in the organization of the hinterland transport. Rail and barge connections might have some positive effects on the port and maritime industry. The aim of this paper is to analyze the cost effectiveness on the hinterland part of the organization in carrier haulage of rail and barge transport from the point of view of the shipping lines. The analyses of the characteristics of sailing and purchasing, of the transport and stowage cost of containers lead to be prudent about the real opportunity to bring out profits on the hinterland thanks to the rail or barge combined transport instead of the road transport. The organization of barge and rail transport is more a tool to bring out profits in the sea part of the transport chain.