Weak bridges have structural weight restrictions imposed because the bridge is unable to carry heavy vehicles. These restrictions are absolute and the bridge may fail if the restriction is ignored.

Environmental weight restrictions are imposed to prevent large vehicles from using inappropriate roads, routes and areas. They are legally enforceable but allow access to property within the restriction. The restrictions aim 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.

There are also recommended lorry routes: preferred routes for lorries through and to major centres in Oxfordshire and delivery routes to central Oxford. These may be backed up by advisory route signing or environmental restrictions, as appropriate.

All restrictions are subject to a Traffic Regulation Order (TRO) and the associated procedures. Regulatory signs are erected on site, which assists the police and Trading Standards in enforcing the TRO. Weak bridges will usually have a diversion route signed.