Assessment of Dynamic Speed Limits on freeway A20 near Rotterdam, the Netherlands

摘要

On the freeway A20 near Rotterdam, the Netherlands, a trial with dynamic speed limits has started on June28, 2011. On a freeway stretch of 4.2 km the speed limit is increased from 80 km/h to 100 km/h as soonas congestion appears to set in and during the night. The aim of the dynamic speed limits is to improve thetraffic operations without deteriorating the local air quality.This paper presents the assessment of this trial with respect to traffic operations, air quality, noiselevel and traffic safety.The traffic operations on the freeway A20 appear to have significantly improved due to the dynamicspeed limits: a decrease in number of vehicle loss hours of 600 (or 20%). This improvement is mainlycaused by an increase of free flow capacity by 4% of the main bottleneck on the stretch. The dynamic speedlimits cause a change in driver behavior such that the median lane is better occupied when flow increases.The air quality reduced slightly. The effects vary along the stretch with a maximum increase inNO_xand PM(_10) emission of 3.7% and 3.6% respectively. However, the effects on the average concentration ofNO_x per year are limited. The noise level appears to slightly increase with 0.2 dB. This increase is mainlycaused during the two peak periods.The indicators for traffic safety show sometimes a (possibly) positive and sometimes a (possibly)negative effect. However, it is not likely that dynamic speed limits have a significant negative effect ontraffic safety.