Factors affecting traffic flow efficiency implications of connected and autonomous vehicles: A review and policy recommendations

Connected and autonomous vehicles are expected to gradually enter the transport modal mix sooner or later. Academic discussions of their expected impacts are well underway, often with conflicting or wide-ranging results. In this chapter, the existing literature is reviewed and summarized, with a focus on the traffic flow efficiency impacts. The expected impacts of autonomous vehicles on the roadway capacity are found not to be unanimous, partly because this seems to depend on the specific modeling conditions. Therefore, common factors that determine whether capacity is expected to increase or decrease are discovered from existing studies, along with determining the factors that influence other traffic flow efficiency-related impacts, such as traffic stability and congestion. An analysis is also performed on the vehicular requirements for autonomous vehicles to serve the mobility demand, and change in vehicle kilometers traveled (VKT) that may happen. Based on the reviewed studies, 19 factors that influence traffic flow efficiency implications of autonomous vehicles are identified and grouped into four categories, namely (i) vehicle characteristics, (ii) travel behavior, (iii) network characteristics, and (iv) policies. The chapter ends with a discussion on policy recommendations in tune with the factors identified. The discussion shows that the policy makers should enact laws to ensure connectivity between AVs to experience significant benefits, integrate CAVs with public transport to avoid mode shifts, incentivize ridesharing to reduce network load, develop suitable parking management policies to avoid empty relocations and introduce congestion pricing to curb induced demand.