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Longitudinal barriers are commonly used to shield hazards, including stiff bridge rail ends and slopes. In some locations, a secondary roadway intersects the primary roadway within the guardrail’s length-of-need (LON). Some intersections have as little as 15 ft (4.6 m) between the intersection and beginning of the bridge railing, which require short-radius guardrail systems. No short-radius systems have been tested and approved to current impact safety standards for shielding hazards with these conditions.
Site conditions provided by the Nebraska Department of Roads were used to determine the constraints for a new safety treatment for intersecting roadways and include intersection radii, bridge railing offset distances, and clear zone distances. An examination of the site conditions determined that the bridge railing end should be treated as a hazard, as defined in the Roadside Design Guide. The hazard would begin at the bridge railing end with a width extending to the clear zone. Several design concepts were developed to treat these situations with a preference on using existing technologies that could be adapted for this hazard scenario.
Fifteen concepts were brainstormed with three considered for further analysis and evaluation. These concepts included net attenuation/end terminal, inertial barrel array/end terminal, and a bullnose with a secondary energy absorber inside of it. All three systems were capable of stopping a vehicle in the space available, but only the net attenuation/end terminal concept was considered likely to accommodate the site conditions using a moderate slope behind the system. Four dynamic bogie tests and two static tests were performed on potential net attenuators to evaluate their use as energy absorbers in the preferred design concept. Recommendations for further development of the net attenuation system were provided.
Advisor: John D. Reid