Potential of Variable Speed Limits for Emission and Noise Reduction on the E313 Motorway to Antwerp, Belgium

The E313 motorway between Liege and Antwerp is one of the busiest links in the Belgian road network. In the direction of Antwerp, traffic jams and accidents are frequent. Many accidents occur at the tail of traffic jams. To warn drivers, variable speed limit gantries and detector loops were installed every 750 metres. When a traffic jam is detected, the speed limit is gradually reduced on the upstream motorway section. This paper investigates the potential of the variable speed limits on emissions (CO2, NOx and PM10) and noise. Next to this, other measure are studied: 1) a general speed limit of 90 km/h 2) a broadening from 3 to 4 lanes 3) a traffic flow reduction. A traffic model of the motorway was constructed with Paramics. Emissions were calculated with VERSIT+ and noise levels with Harmonoise/Imagine. The variable speed limits have no discernible influence on emissions, noise and travel time. A general speed limit of 90 km/h results in a small decrease of emissions while an extra lane results in large emission reductions. Measures that reduce heavy congestion, without attracting more traffic, can decrease air pollutant emissions, but will increase noise emissions.