The downsizing of cars is rapidly decreasing the average size of vehicle on North American highways, yet the largest cargo trucks may become even larger within the next few years. This presents the highway planner with a difficult safety problem. Existing barriers have been targeted at the most common size of vehicle in the traffic mix, but each functions optimally only within a certain range around that target. International Barrier Corporation is developing a barrier system, originally used for motor racing through city streets, which can expand the range of vehicle-to-barrier impacts which a single system can safely contain.
The I.B.C. system is a series of light-gauge steel bins connected end to end to form a chain, and filled with sand. It is not anchored to the ground. The barrier is not translated by impacts from automobiles, but when struck by more massive vehicles can be substantially translated across the ground perpendicular to the length of the barrier. This extreme of dynamic deflection delays or avoids the sharp rise in accelerations which occurs when a barrier's designed deflection limit is reached. During low energy impacts the sand fill "softens" impact and provides continuity of resistance to distortion, thus preventing snagging. Crash tests have demonstrated that this barrier smoothly redirects a 2000 pound car at 60 mph and a 15° angle, and a 4500 pound car at 60 mph and a 25° angle, with virtually no roll or pitch. The corrugated profile completely controls ramping.