Change detection in variable speed limits: failed to look or looked but failed to see?

Variable speed limits (VSL) are used to adjust real-time driver speed to the circumstances of the road condition. Based on theoretical research it has been proposed that change blindness - the failure to detect, identify and localise changes - might play a role in the effectiveness of VSL in terms of perception. To examine whether change detection errors actually affect the perception of changes in VSL under natural circumstances, participants needed to be familiar with the road. To achieve this, twenty-four participants drove the same route nineteen times in a driving simulator on five separate days. Part of the route consisted of a motorway where VSL signs were regularly displayed above each driving lane. In drive nineteen the VSL were changed from 80 km/h to 100 km/h. Driver speed, verbal reports while driving and a questionnaire showed if drivers who did not notice the changed speed limits failed to look at the speed limits or looked at them but just failed to notice they changed. These results are discussed in relation to speed limit recollection, meaningfulness and expectations. This research gives more insight in the extent of change detection errors for VSL and its underlying factors.