The judicial use of crash cushions has saved many lives and reduced the severity of injury to many persons. On new Federal-aid construction, a crash cushion is mandatory where fixed objects cannot be adequately protected by other means. On existing Federal-aid highways, an inventory has been made to identify those locations at which crash cushions can be a definite contribution to traffic safety. Many crash cushion installations have been and are being made. By now, it is almost axiomatic, that fixed objects located hazardously close to the pavement edge should be removed, relocated, redesigned, or shielded. Hazardously close has been interpreted as being within 30 feet, over a relatively level roadside, for highways with high volume and high speed traffic. For other roadside and traffic conditions greater or lesser clearances might be judged hazardous. If shielding is the only practical method of treatment for a fixed object hazard, then either some type of guardrail or a crash cushion (also referred to as an energy absorber, impact attenuator, etc.) will be required. Information received from Federal Highway Administration (FHWA) field offices has indicated that there is some misunderstanding of the basic differences between the "approved" crash cushions. This booklet is an attempt to point out these differences and help designers choose the best type of cushion for the particular location under consideration. It will also attempt to simplify the design of crash cushions.
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