University of California Transportation Center

Excessive vehicle speed on today’s roadways often results in accidents, high fuel consumption rates, and excessive pollutant emissions. Traditional methods of limiting speed have only been moderately effective. Using the latest intelligent transportation technology, speed enforcement can be enhanced through vehicle speed management programs, often referred to as Intelligent Speed Adaptation (ISA). An ISA system monitors the location and speed of the vehicle, compares it to a defined set speed, and takes corrective action such as advising the driver and/or governing the top speed of the vehicle. ISA is an active research field in Europe where it is currently being evaluated. In addition to safety improvements, ISA has the potential to mitigate congestion by smoothing traffic flow during congested conditions, which may also lead to lower fuel consumption and pollutant emissions. In this paper, the energy and emissions impacts of ISA are investigated in detail using both simulation tools and real-world experimentation. This research makes use of state-of-the-art transportation/emissions modeling tools. The simulation analysis is focused on examining different speed management strategies under varying freeway congestion conditions. A set of limited real-world experiments have also been performed using real-time traffic information provided to an ISA-equipped vehicle driving in traffic. Results are compared to another non-equipped-ISA vehicle acting as a control, representing the general traffic flow. Preliminary results indicate that significant reductions are possible for both fuel consumption and emissions without drastically affecting travel time.