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 speed limits? These challenging questions motivate this research project.
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. The proposed work will be the first of its kind from a scientific perspective. It will also be of practical significance, as it could be used to inform the future implementation of more advanced speed limit strategies in urban networks.