Cities all over the world are struggling with congestion problems and its negative impacts. Zurich for example restricts the access to the inner city through a traffic lights control system in order to reduce congestion. The Traffic Engineering Group of the Institute for Transport Planning and Systems (IVT) is trying to improve this access control system by applying up-to-date traffic research to the existing transportation management system of Zurich.
ZüriTraffic is an existing adaptive access control scheme that monitors traffic states in certain streets within the inner city (Image 1). When a predefined level of service threshold is measured, e.g. in the morning rush hour, traffic lights controlling access to the city center are adjusted automatically. The goal is to reduce the number of cars in the inner city and thus reduce total congestion in the overall urban area.
ZüriTraffic’s effectiveness is limited by several factors. First of all, it measures the traffic behaviour in just a few city streets. Secondly, it is based on a static and and therefore eventually out-of-date demand model. Finally, it defines only two traffic scenarios, «congested» and «uncongested,» so it cannot adapt flexibly to continuous changes in network performance.
The innovative ZüriTraffic system may be possible to improve by applying a Macroscopic Fundamental Diagram (MFD), which represents the relationship between the accumulation of vehicles and the number of trips completed in an urban area.
At IVT, a MFD was computed by employing the micro-simulation software VISSIM into a model of Zurich’s inner city network (Image 2). It was shown that the traffic states in the links measured by ZüriTraffic do not necessarily represent the performance of the entire network. Hence, we recommend using the data from the existing 3,500 loop detectors to create a much more effective monitoring and access-control system based on the city’s MFD. Such methodology is independent of the demand patterns and very flexible, as it considers a high number of traffic states as well as the corresponding traffic lights control strategies.
Contact person: Javier Ortigosa
Arnet, K.; Ortigosa, Javier; Ge, Quiao; Menendez, Monica (2012): Study of Traffic Management in the Zürich Area. Presentation at IVT Alumni day. Zurich, March 2012.