We have developed and used a repeatable roof strength survey tool to assess the force resistance characteristics of over 50 passenger car, SUV, pickup, and van roofs. In a rollover, the initial roof-to-ground contact typically fractures and/or separates the vehicle’s bonded windshield. Subsequent trailing-side roof-to-ground impacts apply lateral forces to the roof and its support pillars. In 1971 the National Highway Safety Bureau (NHSB) recognized this rollover sequence and proposed a Federal Motor Vehicle Safety Standard (FMVSS) that tested both sides of the roof in sequence. Our repeatable roof strength survey tool uses a hydraulic cylinder to pull the upper A-pillar, roof rail, windshield header intersection toward the rear of the opposite front door sill imitating the proposed 1971 test, but at a more realistic roll angle. It is used first on one side of the vehicle with the windshield intact before being repositioned on the other side after the fractured and separated windshield is removed and the test repeated. Tests on three vehicles of the same make, model, and model year have validated the repeatability of the test and protocol. Results from all the vehicles demonstrate that in the first side test, the strength of the roof is typically about half the strength recorded in a typical FMVSS 216 test, a further decrease in force resistance occurs after the windshield has failed, and similar elastic restoration of the deformed structure occurs on both sides.

This content is only available via PDF.
You do not currently have access to this content.