Many long-span culverts are subject to loads from heavy trucks, and thus need to be evaluated for their load carrying capacities to estimate safety margins. However, the current manual on bridge evaluation provides limited guidance for bridge-sized culverts due to their distinct structural configurations and different consequences of culvert overload. The project will develop a risk-based approach that can calibrate the varying target reliability levels of culverts and the associated load and resistance factors used for structural evaluation. By investigating all critical risk factors relevant to culver safety under vehicle load, this research will formulate a risk-based methodology for evaluating bridge-sized culverts.