The Traffic Calming Regulations cover the use of overrun area constructed within specified parameters. If local authorities wish to use a design which goes outside these dimensions, they can apply for special authorisation. Traffic Advisory Leaflet 3/93 (see ST 991833 fo) gives advice on seeking special authorisation, and explains that some justification would need to be given why a feature could not conform. Overrun areas are used to create the optical illusion that the useable carriage way is narrower than it actually is. These areas may be employed on bends to encourage car drivers to keep to a low speed but still allow sufficient room for larger vehicles to negotiate them. Similarly they can be used at junctions, particularly roundabouts, to deflect traffic away from a straight ahead and faster path, where the overrunning area allowed larger vehicles to negotiate the junction problems. (A)
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