The purpose of this research was to investigate the critical flare rate and corresponding crashworthiness of a concrete median barrier flaring around a fixed object. The structural capacity and the occupant risk factors of such proposed guardrail system will be evaluated with respect to MASH Test Level 4 (TL-4) criteria through computer simulations and full-scale crash testing. The information compiled from this research provides FHWA and State Departments of Transportation with an acceptable critical flare for cast-in-place concrete barrier system flaring around a fixed object under the 2016 MASH TL-4 conditions. A successfully crash-tested flared concrete barrier system can be applied in situations where flaring a concrete barrier is a need to shield errant vehicles from fixed objects. A concrete barrier crashworthy higher flare rate would result in reduction in flaring length for location where flaring space is an issue. This successfully crash-tested system reduces the risks of injury or fatality for impacting errant vehicles. The flared concrete barrier system reported herein met the performance criteria for MASH TL-4 longitudinal barriers.