Research project Mental models of driving and speed: biases, choices and reality

Mental models describe how people perceive and think about the world including covariances and relationships between different variables, such as driving speed and time.

Research on mental models detected the time-saving bias (Svenson, 1970). It means that drivers relatively overestimate the time that can be saved by increasing speed from an already high speed, for example, 90–130 km/h, and underestimate the time that can be saved by increasing speed from a low speed, for example, 30–45 km/h.

In congruence with this finding, mean speed judgments and perceptions of mean speeds are also biased and higher speeds given too much weight and low speeds too little weight in comparison with objective reality. Replacing or adding another kind of  speedometer in the car showing min per km eliminated or weakened the time-saving bias. Information about braking distances at different speeds did not improve overoptimistic judgments of braking capacity, but information about collision speed with an object suddenly appearing on the road improved judgments of braking capacity.

This is relevant to drivers, politicians and traffic regulators but the results also contibute to our understanding of how people handle numerical information also in other contexts.