Downsizing of domestic passenger vehicles is expected to be a major element in corporate strategies to meet legislated fuel economy mandates. With the expected introduction of significant numbers of mini-sized automobiles in the vehicle fleet, there is a need to re-examine existing roadside safety hardware design and performance criteria.

Current roadside protective device designs and performance criteria are for the most part based on experience with vehicles in the 2,250 to 4,500 lb weight range. An analysis of future vehicle downsizing trends suggests that vehicles as light as 1,700 to 1,800 lb need to be considered.

From available research findings it is known that crash severity increases with decreasing vehicle weight in collisions with pole like structures. High speed off center impacts of small cars into such structures may result in violent multiple rollovers. Thus it is important that the safety performance criteria for breakaway signs and luminaire supports, base bending signs, and other poles and supports be re-examined.

Vehicle geometry, inertial characteristics and crash properties of mini-sized cars may present special problems in the design of traffic railings. Snagging of support posts and vehicle rollover has. been observed in traffic railing tests to date with these small vehicles.

Impact attenuators have been designed to accommodate vehicles in the 2,250 to 4,500 lb weight range. The performance criteria for these devices should be re-examined to consider mini-sized car problems.

In this paper the evolution of the consideration of vehicle size in roadside safety hardware research is reviewed and the data available to assist in the selection of the initial mini-sized cars of interest are discussed. Results from ongoing research efforts aimed at identifying safety problems in such collisions and developing appropriate countermeasures are reviewed.