Citation

Wright C. Transp. Traffic Theory 1983; 8: 673-694.

Copyright

(Copyright © 1983, Publisher varies)

DOI

unavailable

PMID

unavailable

Abstract

In order to limit traffic demand and to keep the road network operating efficiently, most large towns rely on parking controls which are enforced by the police or by traffic wardens. The enforcement is not always effective. In London, for example, it has broken down: many drivers park indiscriminately on yellow lines, and those who park at meters often do so without paying. This paper puts forward a simple model of the interaction between enforcement activity and driver behaviour, and this interaction turns out to be an unstable process which might "collapse" rather suddenly under certain conditions. Essentially, the system is unstable because a traffic warden needs more time to inspect and deal with an illegally parked vehicle than with a legally parked one. If for some reason the deterrent pressure on drivers is reduced below a certain threshold, e.g., fewer wardens are employed, or the impact of the penalty is eroded through inflation, more drivers will park illegally and wardens will no longer be able to cover their "beats". In theory, a collapse is not easily reversed: either one has to employ more wardens, or increase parking penalties. (by analogy, to reverse the polarity of a bar magnet one has to apply a large current to overcome "hysteresis" effects). However, the theory shows that a system can be restored to normal simply by concentrating manpower within selected areas and gradually expanding the patrolled areas over a period of time.