Illegal parking and the enforcement of parking regulations: causes, effects and interactions

Parking enforcement is increasingly perceived as a key feature of urban transport policy. Illegal parking can lead to reduced traffic speeds, congestion, changes in modal choice, loss of revenue from valid parking spaces, a decline in respect for the law and even to accidents. Its potential impact is of such magnitude that it is now widely recognized that policies aimed at its control should be incorporated into any sensible transport plan. However, since parking enforcement is the policy maker's response to illegal parking and in order to implement a response that is appropriate, it is vital that there exists a sound understanding of the causes and patterns of illegal parking. Similarly, the ability to assess the impact of a particular enforcement strategy is equally vital. These considerations, together with the need to specify an overall objective for the enforcement effort, justify the exploration of the various relationships that exist between illegal parking and enforcement. This paper reviews and codifies the relevant available literature and presents these relationships within the general context of transport policy.