Overtaking assistant assessment using traffic simulation

This contribution presents the results of a microscopic traffic simulation study of the potential effects of an overtaking assistant for two-lane rural roads. The overtaking assistant is developed to support drivers in judging whether or not an overtaking opportunity can be accepted based on the distance to the next oncoming vehicle. Drivers have been found to consider this to be a difficult part of an overtaking manoeuvre. The assistant’s effects on traffic efficiency, driver comfort and road safety have been investigated using traffic simulation. The results indicate that this type of overtaking assistant can provide safety benefits in terms of increased average time-to-collision to the next oncoming vehicle during overtaking manoeuvres. This safety benefit can be achieved without negative consequences for traffic efficiency and driver comfort. A driver assistance system that supports the distance judging part of overtaking manoeuvres can therefore contribute to improved traffic conditions on the two-lane rural roads of the future.     

Explaining differences in acceptability before and acceptance after the implementation of a congestion charge in Stockholm

A field experiment was conducted in Stockholm where a congestion charge trial was introduced in 2006. Respondents completed a questionnaire before and after the trial. Acceptance of the congestion charge was higher after the trial as opposed to its acceptability judgments before the trial. Respondents believed the charge had more positive consequences (viz., decreasing parking problems, congestion, and pollution) and less negative consequences (viz., financial cost increases) after the trial than they had expected beforehand. Furthermore, we examined the relative importance of various beliefs for the acceptability of the congestion charge before and after it was implemented. Results are that before the implementation of the charge acceptability was significantly related to beliefs about the expected consequences for one’s own car use and financial costs, whereas acceptance after the trial was related to beliefs about the perceived consequences for one’s own car use and parking problems. These results indicate that acceptance of the congestion charge had increased because people experienced positive consequences of the charge. This conclusion is discussed in the broader context in which the Stockholm trial took place.