Manual for Assessing Safety Hardware TL-4 Evaluation of Critical Flare Rate for Cast-in-Place Concrete Barrier

Abstract

Concrete median barriers are used by Departments of Transportation (DOTs) to provide separation of traffic. Typically, the crashworthiness of these barriers is tested and evaluated in full-scale crash testing conducted according to current roadside safety device standards. Occasionally, DOTs need to flare the concrete barrier length of need (LON) around fixed objects, such as bridge piers. Flaring a concrete barrier increases the effective impact angle which consequently increases the impact severity of the vehicle creating an opportunity for vehicle instability or excessive occupant risk factors. No current recommendations are available to guide the installation of flared barriers around such fixed objects, while still maintaining barrier crashworthiness. Although the current practice is to flare the cast-in-place (CIP) concrete barrier at a maximum 20:1 rate, no full-scale crash testing has been conducted to determine the crashworthiness of the system at this condition or at a flare rate that might be considered more critical. The crash tests reported in this paper were performed according to the Manual for Assessing Safety Hardware (MASH) Tests 4–10 (with the use of a passenger car), 4–11 (a pickup truck), and 4–12 (a single unit truck) for LON, which represent the tests considered necessary to demonstrate the MASH compliance of the device. The 40-in. single slope CIP concrete barrier with a 20:1 flare rate met MASH requirements and is considered MASH compliant for Test Level (TL) 4. The system is considered suitable for implementation where there is a need to flare the concrete barrier around a fixed object.