In-Car Speed Assistance to Improve Speed Management

This paper describes the use of Intelligent Speed Assistance (ISA) and Advanced Cruise Control (ACC), two systems that directly affect speed behavior. Excessive speed (above the speed limit), inappropriate speed (for prevailing conditions), and large speed differences are causal factors in many accidents. The authors note that the development of in-car speed assistance makes it possible to help drivers to choose an appropriate speed, while still complying with the legal speed limits. They also discuss the effects of speed limit credibility combined with ISA and describe both the direct effects on speed and the derived effects on safety, traffic efficiency and the environment. The expected safety effects of the various ISA types are most promising, although it is not clear yet when and to what extent the expectations can become reality. The paper focuses on important factors regarding adequate deployment, including driver acceptance, positions of the major stakeholders, and implementation strategies. The authors report on simulation and real-world studies of both ISA and ACC systems, primarily conducted in the Netherlands and Sweden. They conclude that, for all types of ISA, promising effects are predicted, particularly regarding safety. Automatic controlling ISA is most effective, but at the same time has the lowest driver acceptance. In addition, dynamic speed limits increase the positive effect of all ISA types.