SPEED
Rethinking speed limits in urban networks
Duration
08.2016-07.2019
Sponsor
ETH Zurich Research Commission
Staff
Dr. M. Menendez and L. Ambühl
Summary
In the last decades, cities around the world have started to reduce speed limits in both residential areas and city centers. In Switzerland, for example, more than 700 districts and municipalities have streets and areas with 30 km/h regulations, and there have been initiatives to extend those to whole cities. These speed limit reductions typically seek improvements in traffic safety, as well as livability and sustainability. Many cities implement speed policies based on the experience from others, intuition, or depending on the political leadership. In most cases, however, they lack a real understanding of the breadth and depth of impacts from these strategies, especially from a traffic operations point of view. What are the fundamental effects of different speed limits on network-wide traffic operations? Can we manage urban traffic by regulating the speed limits? These challenging questions motivate this research proposal.
Our objective is to understand the effects of speed limits on the traffic dynamics of urban areas from two important perspectives: a strategic one that aims to influence planning decisions, and an operational one that aims to influence real-time traffic management.
In Part I, we will evaluate urban traffic performance under representative speed policies and different network features. We will generate and combine various speed-policy scenarios –– in both abstract grid networks and real networks (Zurich). A microscopic simulation will be employed to emulate the drivers’ routing behavior in response to different policies, and understand the resulting propagation patterns of congestion. Given these comprehensive results, we will develop general guidelines regarding speed limits and their impacts on traffic.
In Part II, we will focus on the development of an innovative control strategy based on dynamic speed limits, i.e. Urban Variable Speed Limits (UVSL). Our approach will consider multiple regions within the city with different speed limits, which creates a rather challenging control problem. Employing an innovative macroscopic perspective, we will build a modeling and optimization framework to obtain the optimal speed limits for each region in real-time, paying particular attention to the effects on the spatial distribution of traffic in the overall network. Both analytical and simulation tools will be utilized to test the proposed speed control strategies.
The proposed work will be the first of its kind from a scientific perspective. It will also be of practical significance, as it will be used to inform the future implementation of more advanced speed limit strategies in urban networks.