Modeling crash frequencies at highway-railroad grade crossings in Kentucky in the United States

Previous safety studies at highway-railroad grade crossings (HRGCs) have typically examined crash severities. However, there remains a notable gap in studies that developed safety performance functions (SPFs) (or crash frequency models) at these critical locations. This study develops SPFs for both total and fatal-and-injury (FI) crashes at HRGCs in the state of Kentucky in the U.S. using ten years (2014-2023) of crashes. The study merged extensive crash records and roadway attributes from the Kentucky Transportation Cabinet (KYTC) and Federal Railway Administration (FRA). Additional effort was made to manually collect geometric and infrastructure features nearby HRGCs (e.g., skewness, presence of exclusive turns, presence of channelizing island, and different sign types). The negative binomial "NB", heterogeneous NB "HTNB", Conway-Maxwell-Poisson "CMP", and heterogeneous CMP "HTCMP" models were fitted to handle data over-dispersion. The HTCMP model (with varying dispersion parameter) demonstrated the best performance. The model results showed that urban locations with poor illumination, fewer number of warning bells (≤2), the absence of track signals, and skewed geometry were associated with increased crash frequencies. Angle and rear-end HRGC-related crashes were predominant at the high-crash-prone HRGC locations, often involving left-turn movements and driver distractions. Key risk factors varied between total and FI crashes, with features like the presence of stop lines, the presence of parking structures, skewness, and the number of through lanes differently influencing each model. Based on the model findings and high-crash location analysis, several countermeasures were recommended near HRGCs, e.g., installing high-intensity LED lighting to improve nighttime visibility, and installing static signs (skewed-intersection warning and distracted driving).