Traffic congestion and the resulting stop-and-go motion of traffic on freeways increases travel delay, consumes more fuel and poses greater crash risks to motorists. Variable speed limit (VSL) control, where motorists are advised to travel under a lower speed limit on certain sections of the road, has been used to smooth traffic flow and reduce congestion. This research brief summarizes findings from the project which developed VSL control strategies to reduce fuel consumption and emissions on a freeway with multiple bottlenecks. The core objective was to minimize fuel use and emissions with no or minimal increase of travel time.

Key words: Variable speed limit, traffic throughput, emissions and fuel consumptions, microscopic simulation, probe vehicles