NCJ Number
81162
Journal
Police Research Bulletin Issue: 37 Dated: (Autumn 1981) Pages: 4-9
Date Published
1981
Length
6 pages
Annotation
This article describes the operation of an automatic vehicle number plate reading system being developed in England by the Police Scientific Development Branch. Its main use will be to detect and apprehend the drivers of stolen cars.
Abstract
The automatic number plate reading system is designed to interface with the Police National Computer database, providing the capability of rapidly checking large traffic flows for stolen vehicles. A conventional television camera with infrared capability, is used to pick up an image of the front or back of a car including its number plate. Infrared illumination enables covert night or daytime working, and a vehicle sensor buried in the road ensures that the system only looks at the vehicle's image when it is in focus. The signal from the television camera is processed electronically to extract the vehicle registration mark, recognize it and search the database. Finally, if a stolen vehicle has been detected, an alarm message is generated either locally at the site or remotely to a patrol car or police station. The total time taken by the system in detecting a stolen vehicle is about 5 seconds. When the television image is of a high quality the recognition rate is over 90 percent but factors such as dirty number plates, poor weather conditions, and different character fronts on the plates may cause image degradation. False alarms may occur when the system misreads a number plate or by chance finds a match on the stolen vehicle database. Experiments are still underway to improve the recognition rate in adverse conditions and limit the false alarm rate. According to the planned timescale, the installation of the first automatic number plate reading system in the world will be completed by June 1981, and operational trials with a police force are to start 6 months later. Illustrations are given.