Underride

Underride is a term used in road safety to describe an accident in which a smaller vehicle slides beneath the underside or side of a larger vehicle, most often a heavy truck or trailer. In many underride crashes, the intrusion into the passenger compartment is severe, leading to serious injuries or fatalities even when the visibly damaged vehicle appears undamaged.

Rear underride occurs when a car collides with the rear of a trailer or tractor-trailer, potentially sliding under the bumper. Side underride happens when a vehicle becomes trapped against the side of a truck; front underride is relatively uncommon but can occur when a vehicle collides with the front of a truck or when a car moves under a truck during a turn or rollover.

Underride guards, also called underrun protection, are structural devices designed to catch or divert a vehicle before it slides under. They are required on many trailers in different jurisdictions, with additional side guards used in some regions. Guard performance depends on speed, impact angle, and the design of the vehicle.

Regulatory frameworks vary by country and region. The United States has federal standards addressing rear underride protection on trailers and some requirements for certain trucks; the European Union and other regions have separate regulations emphasizing side underride protection and different testing protocols.

Underride remains a safety concern in road transport, with ongoing engineering, regulatory, and enforcement efforts aimed at reducing the frequency and severity of such crashes.