Weight restrictions can be imposed for structural or for environmental reasons. It is legal control on a specified vehicle weight or width, mainly on lorries, on certain roads and routes.

The restriction prevents large vehicles from using inappropriate roads, routes and areas in order to:

• Reduce danger to pedestrians and other road users
• Prevent damage to buildings, roads and bridges
• Preserve the character, amenity and environment of an area
• Reduce and manage congestion on the roads
• Procedures for implementation
• Restrictions are subject to a Traffic Regulation Order (TRO) and the associated procedures (see Fact Sheet on Traffic Regulation Orders)
• Regulatory signs are erected on site to give effect to the TRO and to assist the police in carrying out its enforcement

This is a matter for the Police. However, the Police have limited resources to enforce this type of restriction (especially environmental restrictions). Restrictions with "except for access" clauses quickly fall into disrepute and are notoriously difficult to enforce. However these are needed to permit HGV access to local shops, businesses, residential properties for deliveries/removals etc.

For this reason, enforcement commands a low priority and therefore, where possible, physical measures should be introduced to prevent any abuse of the restrictions - the installation of signs alone are wholly ineffective. Restrictions will not be used if there is no suitable alternative route for the displaced traffic.

Where a Traffic Regulation Order restricts the use of a road, route or area to certain vehicles, the signing of a recommended alternative route will need to be considered.