W-beam guiderail transition from light to heavy posts.

Two full-scale crash tests evaluated a transition between light-and heavy-post w-beam guiderail. The transition consisted of lowering the rail height from 30 to 27 inches and reducing the spacing of the light posts as the heavy-post section is approached. The crash-test impacts were just upstream of the heavy-post section using 1,800- and 4,500-pound sedans. Test results were generally acceptable in terms of national co-operative highway research program (NCHRP) criteria. Although the exit trajectory of the 4,500-pound sedan exceeded the recommended threshold limits, the vehicle was not judged to present a significant threat to other vehicles.