When light poles are installed within the deflection zone of roadside barriers (guardrails), they may influence the ability of the guardrail to redirect an impacting vehicle safely. One concern is that, during an impact, the vehicle may pivot about the relatively rigid light pole and then spin away from the guardrail back into the traffic stream in an uncontrolled, unsafe manner. The objective of this project was to determine if light poles have an adverse effect on the redirecting performance of guardrails. The project included six full-scale crash tests involving two vehicle weight classes (2000P and 820C), two light pole base designs (AT-A and AT-X), and a typical guardrail used in Ohio [Type 5 (W-Beam)]. All full-scale tests were carried out according to the recommended procedures in National Co-operative Highway Research Program (NCHRP) Report 350. The actual vehicles used for the 2000P class were 1/2 ton pick up trucks ballasted to simulate the weight and mass characteristics of the 2000P vehicle that is specified in NCHRP Report 350. The guardrail/light pole system was not shown to cause snagging or subsequent unstable motion of the vehicle due to impact. All vehicles exited the guardrail in a stable manner. No change in the arrangement of light poles behind the Type 5 guardrail is contemplated. The redirecting function of the guardrail was not compromised as a result of placement of the light pole behind the length of need. Excessive exit angle situations (per NCHRP Report 350) occurred in three tests involving the simulated 2000P class vehicles. However, the impact conditions employed for these tests were extreme, and the likelihood of this situation occurring under everyday highway usage may be small. For the covering abstract see ITRD E116488.
Abstract