How the presence of passengers influences the risk of a collision with another vehicle.

The risk of a collision with another vehicle due to the presence of passengers is analysed in detail in a large sample of accidents from Mittelfranken, Germany, from the years 1984 to 1997. Using a responsibility analysis, the overall effect of the presence of passengers and the influence of modifying variables is examined. While a general protective effect of the presence of passengers is found, this is reduced in young drivers, during darkness, in slow traffic and at crossroads, especially when disregarding the right of way and passing a car. These findings are interpreted as a general positive effect of the presence of passengers who influence the driver's behaviour towards more cautious and thus safer driving behaviour. However, passengers may also distract drivers' attention in an amount which cannot be compensated for in all situations and by all drivers by cautious driving. Besides educational measure, a potential solution to this problem may be driver assistance systems which give an adapted kind of support when passengers are present.