In 1966 the annual fatality rate for traffic accidents in the united states had reached 50000. Approximately 40% of the accidents were single car accidents and the majority of the fatal accidents occurred when the errant vehicles struck fixed objects located within 30 feet (9 meters) of the roadway. It was concluded that fixed objects must be shielded by either the use of guardrails or impact attenuators. Many different types of attenuators were conceived. Two types emerged as being practical; the inertial barrier type and the compression type. There are presently two inertial barrier systems and six compression types in use. The compression types generally redirect vehicles impacting on their sides and in most instances are reusable even after being impacted head-on. Attenuators are used to protect median barrier terminals, guardrail ends, utility poles, trees, bridge abutments, gore noses, and other fixed objects. Records while subjective in nature, indicate that since the first use of attenuators as many as 10000 lives may have been saved and as many as 25000 serious injuries prevented.(a) for the covering abstract of this volume see irrd 257235. For covering abstracts of other volumes see irrd 257174, 257182, 257202 and 257267.
Abstract