Opportunities to improve speed behavior: credibility of speed limits and the use of ISA

Speeding is still common practise on many roads and contributes to a significant number of crashes. Intelligent Speed Assistance (ISA) systems aim to reduce speeding in a more or less intrusive manner. This is promising, however, the acceptability of ISA systems is still very low. Another promising approach to reduce speeding is by improving the credibility of speed limits. A driving simulator study is conducted to investigate the effect of credibility, with or without using an open informative and warning ISA. The results show that both ISA and credibility of speed limits are effective measures to reduce speeding. Non-ISA users appear to be more sensitive for the credibility of speed limits than ISA users.