Organisation: Department for Transport
Date uploaded: 16th September 2010
Date published/launched: May 2009
A review of the research literature from 1995 to 2006
Speed affects the difficulty of the driving task. Drivers choose a speed to keep difficulty within an acceptable range. This varies among drivers. Inexperienced drivers are most likely to underestimate task difficulty. Speeding may arise from the normal process of speed adjustment to conditions which elicit a higher speed than the posted limit – but this speed is not corrected downwards. Speed may be influenced by motives that are typical of the individual (aggressiveness), or are acute (making up time). Influences that raise speed also raise the difficulty of the driving task and reduce safety margins.
Main findings
• For most of the time on the road, drivers choose a speed that maintains an adequate margin between task demand and their capability.
• Safety consequences arise where the driver is poorly calibrated (i.e. in terms of underestimating task demand and/or overestimating capability), or where the driver operates with too high a risk threshold.
• For some drivers a high risk threshold appears to be a trait, and is associated with drivers who are immature or have characteristics of sensation seeking, aggression, poor self-control and social deviance.
• For most drivers there are also situational determinants that may have the effect of raising risk thresholds by motivating increases in speed. These include an emotional state of anger and the motivation to save time.
• Drivers described as having a ‘reactive’ driving style may be particularly vulnerable to such influences.
• Some drivers may also be subject to normative pressures to conform to the apparent speed of others, which they overestimate.
For more information contact:
Neale Kinnear