Understanding Road Signs and Traffic Rules: Does it contribute to road safety?

Behaviour-based driver risk assessments have been available to fleet companies via DriverMetrics™ since 2005 and from time to time we are asked why our assessments do not take into account driver knowledge when we assess the risk of driving for work. The rationale behind this decision is the subject of this brief article.

Regulatory authorities and fleet-based organisations often use knowledge of road signs and traffic rules as a measure of driver competence and road safety. Many driver risk assessments available to fleet companies include questions to test driver knowledge of the Highway Code for example. The assumption being that the ability to recognise road signs means better the driver must be safer than a driver that fails to score well. Intuitively it makes sense to think that poor driver knowledge would result in greater crash risk and a lack of understanding about traffic rules may lead to increased levels of traffic offending. But is this assumption valid according to the evidence base?

We undertook a review and found little evidence that this assumption can be verified. One of the earliest studies of more than twenty thousand drivers, found no associations of any significance between errors on a knowledge test about driving and traffic violations over more than four years Conley and Smiley (1976). The researchers concluded that passing this type of test was a mere formality for driver licensing which had nothing to do with safety. A couple of decades later, Gebers (1995) correlated knowledge acquisition on a course for traffic violators with their crashes and violations. Violations, but not crashes, were weakly associated with an increase in knowledge, but there were methodological weaknesses in this study.

At Cranfield University, we recently published a study of responses to an online Highway Code test in which scores on four knowledge tests were correlated with self-reported collisions and driving offences in the previous 6 months (Wahlberg and Dorn, 2012).. We found that the correlations (strength of association) for knowledge scores and crash involvement were close to zero, meaning that there was no association between knowledge score and crash involvement. For traffic offences significant associations were found for two knowledge tests but the coefficients suggest that these findings may not be of any practical significance and would require replication. Our research concluded that knowledge of road signs and traffic rules and laws may have little bearing on road safety.

The correlations between  knowledge test scores, collisions and penalty points reported for the previous six months. N=318

Measure of Driver Knowledge Collisions Points
Failures (number of times knowledge test was failed) -.03 -.01
Safety Margins -.07 -.11*
Overtaking rules -.05 -.07
Attitude and Alertness .01 -.02
Anticipation and Hazard Perception .00 -.11*
All modules mean -.04 -.14*

* p<.05

Previous research has also suggested a weak (at best) relationship between driver knowledge. A randomly allocated group of drivers who were required to pass a test about traffic law showed no difference in crash involvement compared with those who did not take part in such a test (Janke, 1990). Arthur and Doverspike (2001) also found a poor relationship between the scores from a driving knowledge test and at-fault crashes over three years. A similarly weak association was found between driving knowledge and recorded crashes (Barkley, Murphy, Du Paul and Bush, 2002) amongst young drivers.

Whilst we would not disagree that basic knowledge of the Highway Code and traffic rules is necessary for elementary driving competence, but to assume that this is important for road safety has not been demonstrated at least not in the public domain. The reason for the lack of association may be because most crashes are contributed to by behavioural and human factors rather than knowledge of the Highway Code. DriverMetrics™ continues to ensure that their driver risk assessments are evidence-based and capable of discriminating between safe and unsafe drivers to help organisation deliver more effective and targeted educational interventions.


Arthur, W., Jr., & Doverspike, D. (2001). Predicting motor vehicle crash involvement from a personality measure and a driving knowledge test. Journal of Prevention and Intervention in the Community, 22, 35-42.

Barkley, R. A., Murphy, K. R., Du Paul, G. J., & Bush, T. (2002). Driving in young adults with attention deficit hyperactivity disorder: Knowledge, performance, adverse outcomes, and the role of executive functioning. Journal of the International Neuropsychological Society, 8, 655-672.

Conley, J. A., & Smiley, R. (1976). Driver licensing tests as a predictor of subsequent violations. Human Factors, 18, 565-574.

Gebers, M. A. (1995). Knowledge and Attitude Change and the Relationship to Driving Performance among Drivers Attending California Traffic Violator School. RSS-95-147. California Department of Motor Vehicles.

Janke, M. K. (1990). Safety effects of relaxing California’s clean-record requirement for driver license renewal by mail. Accident Analysis and Prevention, 22, 335-349.

af Wåhlberg, A. E., & Dorn, L. (2012). Knowledge of traffic hazards – does it make a difference for safety? In Sullman, M. & Dorn, L. (Eds) Traffic and Transport Psychology. Ashgate: Aldershot.