In-service, performance-based roadside design policy: Preliminary insights from Washington State's bridge rail study

Empirical insights about the performance of in-service roadside hardware are presented. A statistical study of bridge rail impacts on vehicular accident severity is presented from data collected in Washington State. In particular, concrete balusters and metal rails underperformed in comparison with the average bridge rail type, whereas thrie-beam guardrails and safety shape barriers had superior performance. The study presents a statistical framework that is particularly suitable for capturing real-world, unobserved effects that impact reported accident severity distribution. Policy sensitivities show systemwide savings through upgrading the underperforming rails to provide substantial performance. The combination of insights from the relative performance of bridge rails and the associated policy sensitivities provides direction for national policy on roadside design. In particular, the insights offer some strategic direction on inexpensive upgrades to state-level decision making.