The use of a microscopic traffic simulation model to evaluate the impact of a wide installation of active speed limiters on traffic flow characteristics and on safety was investigated. The traffic simulator models the acceleration and lane changing behavior of individual vehicles in detail, and so captures not only the impact of speed limiters on equipped vehicles but also the interaction between equipped and non-equipped vehicles and the resulting impact on non-equipped vehicles. In the experiment, the impact of various factors including the limiter set speed, the mean desired speed, and congestion level was included. The impacts are quantified in terms of the average and distribution of speeds, the numbers of lane changes performed and the predicted impact on the rates of injury and fatal accidents. The impact of the speed limiters penetration rates on these statistics was also evaluated. The simulation results show that speed limiters have significant effects on the speeds driven, the variability of speeds and frequency of lane changing, but not on traffic flows. Active speed limiters can reduce traffic speeds by as much as 10%. This result is comparable with field and driving simulator evaluations. The variability of traffic speeds may also significantly be reduced when speed limiters are used, especially for the higher desired speeds and congestion levels. Consequently, a significant desired reduction in the accident rate might be reached. Speed limiters also have an impact on the number of lane changes drivers undertake. Generally, the impact of speed limiters is more pronounced when their settings are more restrictive compared to uncontrolled traffic speeds in the section. They are also generally most effective in the middle range of congestion levels, where they have a moderating effect not only on equipped vehicles but also on non-equipped ones. For the covering abstract see ITRD E137145.
Abstract