overheight

Overheight refers to a vehicle, payload, or equipment whose height exceeds the maximum allowed for a given roadway, bridge, tunnel, or other structure. Height limits are determined by transport authorities and vary by jurisdiction, route, and intended use. The term is used alongside overwidth and overlength to describe oversized loads that require special handling.

On roads, the danger of an overheight vehicle is collision with overhead structures such as bridges, tunnels, gantries, or power lines. Height is measured from the road surface to the highest point on the vehicle, including structures protruding from the roof. Clearances are posted as signs with a maximum height, often in feet/inches or meters, and are also depicted on route planning tools.

Preventive measures include route planning, permits, and sometimes escort vehicles; some jurisdictions require pre-approved routes, temporary height restrictions, or travel during specific hours. Detection systems and height-clearance signs warn drivers; if an overheight situation is detected, drivers are advised to detour or stop. Rerouting may require removing equipment or altering the load.

Impacts and enforcement: collisions can cause structural damage, traffic disruption, and injuries; authorities may impose penalties, and transport operators can be fined or held responsible for remediation. In some cases, authorities may temporarily ban travel on certain routes until the hazard is resolved.

Examples: common road environments place typical highway clearances around 4.0 to 5.0 meters (13 to 16 feet); urban tunnels may be lower. Railway and aircraft-related clearances have their own standards.