Abstract
A review of accident experience shows that collision with fixed highway onstacles is an important factor. Cushions constructed of water-filled plastic cells have been tested and found effective in reducing the severity of barrier impacts. Human tolerance data are briefly reviewed. Data of several cushioned and unprotected barrier collisions are compared in terms of vehicle crush, vehicle rebound and coefficient for restitution, measured vehicle acceleration histories, and the Gadd index of severity applied to vehicle measurements.