Development and Evaluation of Crashworthy Approach Guardrail Transition with Increased Span Length between Concrete Bridge Rail and First Transition Post – Phase I

Authors

Tewodros Yosef, University of Nebraska-LincolnFollow
Qusai Alomari, University of Nebraska-LincolnFollow
Ronald K. Faller, University of Nebraska-LincolnFollow
Robert W. Bielenberg, University of Nebraska - LincolnFollow
Scott Rosenbaugh, University of Nebraska-LincolnFollow

Date of this Version

1-2026

Document Type

Article

Citation

Yosef, T.Y., Alomari, Q.A., Faller, R.K., Bielenberg, R.W., and Rosenbaugh, S.K. (January, 2026). Development and Evaluation of Crashworthy Approach Guardrail Transition with Increased Span Length between Concrete Bridge Rail and First Transition Post – Phase I. NDOT Research Report TRP-03-503-25.

Abstract

This study developed and evaluated a 34-in.-tall Nebraska Department of Transportation (NDOT) thrie-beam approach guardrail transition (AGT) with an increased span between the concrete buttress end and the first transition post. The objective was to accommodate a wide range of common obstructions near bridge ends, including abutments, wing walls, drainage features, and utilities. A survey of NDOT districts identified critical obstruction geometries and informed design criteria. Most NDOT districts indicated that a maximum span of about 4 ft would be sufficient, and some preferred spans up to 6 ft. To accommodate a wider range of obstructions, the first transition post was set 8 ft-51/4 in. from the concrete buttress, more than twice the post spacing used in other MASH transitions. A validated LS-DYNA model of the standard 34 in. NDOT AGT system supported concept design screening under the Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3). The selected configuration used a double-tube design with HSS 4 in. × 4 in. × 1/4 in. members based on performance, handling weight, and connection demand. Simulations for MASH test designation nos. 3-21 and 3-20 showed stable vehicle behavior, acceptable occupant risk measures, and component stresses below yield and ultimate limits. Critical impact points were 89 in. upstream of the concrete buttress for MASH test designation no. 3-21 and 65 in. upstream of the concrete buttress for MASH test designation no. 3-20. Reverse direction and upstream impacts showed no significant pocketing or snag. Overall performance matched the standard NDOT 34-in. tall AGT system. The long-span design provides a crashworthy and practical option for non-ideal sites. Full-scale vehicle crash testing is required to confirm compliance and support FHWA eligibility.