Intrinsic vs. extrinsic motivation
Psychologists have pointed out that speed enforcement is essentially an extrinsic motivational approach that relies on negative, external factors like fear of punishment, to change drivers' speed behaviour. It would diminish the intrinsic motivation of drivers to conform to the law, i.e. because they want to. The use of punishment instead of reward can be considered as a one-sided psychological approach.
Ideally, traffic enforcement is supported by social norms in a society. Visible police enforcement operations then ‘remind’ road users of the importance of rules and urge them to comply with traffic rules. Whereas, at first, rule compliance may be extrinsically motivated by the aim to avoid punishment, later on drivers may actually change their personal belief about what is the right behaviour and internalise traffic rules.
Over the last four decades, under the combined influences of new laws, police enforcement, and public communication campaigns, many drivers worldwide have come to accept the rule ‘no drinking and driving’ as a strict, personal norm. This positive development towards an intrinsic motivation for a traffic rule is probably more difficult to achieve for speeding behaviour. For many drivers, the relation between personal speeding and crash risk is less evident than the relation between alcohol and crash risk. More information about the effect of speed on crash and crash severity may help to increase the intrinsic motivation to comply with the speed limit.