Dynamic modelling of traffic congestion

Traffic management is becoming a more frequently considered technique for improving road infrastructure operation than in the past. On the one hand, the economic, environmental and social costs of building new roads are such that traffic flow management is now a preferred solution. On the other hand, while for many years the operational contribution of traffic theory was limited by the lack of traffic data, recent advances combined with the boom in measurement systems mean that real-time flow control has now become a reality. This makes it possible to influence the dynamics of traffic flow, of which congestion is the best example, and to envisage new traffic regulation solutions or innovative developments.

Even if road traffic regulation is not the only solution to congestion problems, it is certainly the most important, least costly and most promising of the available tools. Behind this notion lie systems that seek to modify either transport supply or travel demand. The aim is to achieve a better match between the two, whether in time or space. When demand (the number of vehicles on the road) exceeds supply (the maximum number of vehicles that can fit on the road), congestion occurs. Congestion thus arises where the network's supply is insufficient to meet demand. Congestion can be localized in space and time (peak periods, incidents, etc.). The aim of traffic control is to adapt traffic demand and road supply (capacity) to improve use of the transport system. Traffic regulation applies to both flow control and user information.

Classically, traffic regulation measures include infrastructure access control, dynamic regulation of speed limits and the dissemination of real-time information to users. These measures were initially deployed to increase the efficiency and reliability of the transport system, but also to improve road safety, for example by informing service vehicles on freeways and ring roads of a traffic jam ahead.

The benefits of traffic regulation are still poorly understood. Indeed, to do so, it is necessary to be able to assess the benefits of the combined deployment of several measures. It's an arduous task, but the scientific community is convinced that traffic regulation has positive effects. For example, the Dutch Institute for Traffic Analysis estimates that traffic regulation reduced the time lost to congestion by 14% between 2000 and 2010. What's more, flow control encourages different players such as local authorities, public transport operators and the private sector to act in a coordinated way, and to cooperate to ultimately improve the situation collectively. Technological advances are making this increasingly easy. All these reasons suggest that traffic regulation needs to be developed on a large scale....