The effects of a driver assistance system for safe speed and safe distance – A real-life field study

The effects of a driver assistance system for keeping safe speed and safe distance (referred to as SASPENCE) on driver behaviour, reactions and acceptance were evaluated in a test carried out in 2006. Twenty test drivers, recruited by ads, drove two times (once with the system off and once with the system on) in real traffic conditions along a 50 km long test route containing urban and rural roads and motorway sections outside Turin, Italy. Driving data was logged and the test drivers were observed by means of an in-car observation method, in this case by two observers riding along in the car with the driver. Driver opinions were collected through questionnaires. The findings show positive effects of the system in terms of fewer alarm situations, shorter alarm lengths, shorter reaction times, increased headway and better interactions with vulnerable road users at intersections. On the negative side, driver performance worsened slightly, the number of centre line crossings increased, there was worse facilitating behaviour with regard to other drivers and harder braking at traffic lights. No major effect on speed behaviour of the driver, lane choice, lane keeping, lane change, overtaking, red running, use of turning indicator and workload was found.