Abstract
Collision with a fixed object has been found to be the leading source of fatalities on our Interstate Highway System and other freeways. Among the efforts to reduce this toll has been the developments and installation to impact attenuators on an experimental basis in a number of States at elevated exit ramps. Accident experience with these devices has been encouraging and several barrier types are now considered operational. Research is now underway to develop new types of energy absorbing barriers and to improve the performance of existing types.