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Placement of Breakaway Light Poles Located Directly Behind Midwest Guardrail System (MGS)




Mojdeh Asadollahipajouh, Bob Bielenberg, Jennifer Rasmussen (Schmidt), Jessica Lingenfelter, Ronald Faller, John Reid




Light poles are commonly installed along highways to provide proper illumination in critical areas. When placing utility poles in close proximity to guardrail, the poles may affect the guardrails ability to safely contain and redirect vehicles by creating unwanted stiffening or hinging of the barrier system around the pole. The pole may also present a snag obstacle to impacting vehicles and induce vehicle instabilities. In this study, the lateral offset between the face of the light pole and the back of the post was evaluated. The minimum safe lateral offset was determined to be 20 in. (508 mm) through crash testing and computer simulation with non-linear finite element analysis. Two crash tests were conducted according to the American Association of State Highway Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) impact safety criteria. In test no. ILT-1, a 5,000-lb (2,268-kg) pickup truck impacted the combination Midwest Guardrail System (MGS) laterally offset 20 in. (508 mm) in front of a luminaire pole at a speed of 62.6 mph (100.7 km/h) and an angle of 25.2 degrees. In test no. ILT-1, the pickup truck was captured and safely redirected while impacting the luminaire pole and disengaging it at base. In test no. ILT-2, a 2,420-lb (1,098-kg) small car impacted the MGS laterally offset 20 in. (508 mm) in front of a luminaire pole at a speed of 62.7 mph (100.9 km/h) and an angle 24.8 degrees. In test no. ILT-2, the car was safely contained and redirected while minimally contacting the luminaire pole. The MGS provided acceptable safety performance under MASH TL-3 when critically impacted by a pickup truck and a small car. Thus, a minimum lateral offset of 20 in. (508 mm) between the back of the post and front face of the breakaway pole was sufficient to assure a safe performance of the MGS during vehicle impacts without undesired interaction with the pole. Accordingly, guidance was provided for safe pole placement behind the MGS.


Highway Safety, Luminaire Poles, Crash Test, Roadside Appurtenances, Compliance Test, MASH, Breakaway, Light Poles, Clearance Distance

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