What Is The Mansfield Bar

A Mansfield bar is the commonly used name for the rear underride guard fitted low across the back of many semi-trailers. The guard is designed to help prevent a smaller passenger vehicle from sliding underneath a trailer during a rear-end crash. Without an effective underride guard, the trailer can enter the passenger compartment above the car’s normal front-end crash structures, creating a serious risk of fatal or catastrophic injuries. The term is associated with actress Jayne Mansfield, who died in a 1967 collision in which the car she was travelling in went underneath the rear of a tractor-trailer. The safety component may also be called a rear impact guard, underride guard or, informally, an ICC bumper. Federal regulations establish standards for rear impact guards on many trailers. Not every bar or bumper on a commercial vehicle is technically a Mansfield bar, but when people use the term they usually mean the horizontal rear underride protection fitted to a semi-trailer.