RELIABILITY-BASED DESIGN OF SIGHT DISTANCE AT RAILROAD GRADE CROSSINGS

The existing method of sight distance design at railroad crossings is deterministic. This paper presents a probabilistic method that account s for the variations of the component design variables and their corre lations. Two cases are considered. Case 1 addresses the sight distance needs along the highway and the railroad for an approaching vehicle. Case 2 addresses the sight distance needs along the railroad for a sto pped vehicle. The probabilistic method is based on the advanced first- order second moment of reliability analysis. Case 1 is modeled as a sy stem with two parallel components. The probability of failure of each component and the system probability of failure are developed. Case 2 is modeled as a single-component system, and a design graph for sight distance needs along the railroad is presented. The method is validate d using Monte Carlo simulation; its application is illustrated using n umerical examples; and the sensitivity of the design variables is exam ined. The proposed method should result in safer operations at railroa d grade crossings.