The development of a method to measure speed adaptation to traffic complexity: identifying novice, unsafe, and overconfident drivers.

To monitor novice driver performance in the first years of solo driving, a test aimed at assessing speed adaptation to the traffic situation was developed and evaluated. The Adaptation Test consisted of 18 traffic scenes presented in two (almost) identical photographs, which differed in one single detail, increasing the situation's complexity. As the pictures were presented randomly and participants could not return to previous pictures, participants were kept unaware of the complexity differences in the pictures. The difference in reported speed between the two pictures was used as an indication of drivers' inclination to adapt their speed to the complexity of the traffic situation. Results showed that novice drivers (n=434) performed worse on the Adaptation Test (i.e. less often reported a lower speed in the more complex situation) than experienced drivers (n=173). In addition, unsafe drivers and overconfident drivers, as identified in an on-road driving assessment, performed worse on the Adaptation Test. This indicates that the Adaptation Test is effective at measuring adaptation of driving speed to the complexity of the situation; and that incorrect self-assessment, and overestimating driving skills in particular, may have a negative effect on speed adaptation.