Investigating motorcycle crashes pre- and post-COVID-19 pandemic along Kentucky's urban roadway segments.

Background: This study developed safety performance functions (SPFs) for motorcycle-related crashes along Kentucky's urban roadway segment facilities (separately along both two-lane undivided and multilane road segments) for each of the pre-COVID-19 pandemic (2015-2019) and post-pandemic (2020-2022) periods. A total of 2,963 motorcycle crashes over eight years (2015 through 2022) across 2,642 urban roadway segments and several road-specific features (e.g., shoulder width and annual average daily traffic "AADT") were used.

Methods: The Conway-Maxwell-Poisson (CMP) model and heterogeneous Conway-Maxwell-Poisson (HTCMP) model "that accounts for unobserved heterogeneity" were applied and compared.

Results: For both urban two-lane undivided and multilane segment facilities, the HTCMP models outperformed their CMP counterparts pre- and post-pandemic, based on various goodness-of-fit measures (e.g., Akaike information criterion "AIC" and pseudo R2) and prediction performance (e.g., mean absolute deviance "MAD" and mean square prediction error "MSPE"). From the fitted SPFs, higher AADT and presence of horizontal curve were significantly associated with increased motorcycle crash frequency, while the presence of roadside steel strong-post W-beam guardrail was significantly associated with reduced motorcycle crash frequency along all urban segments, both pre- and post-pandemic. Furthermore, posted speed limits (≥55 mph) were significantly associated with reduced motorcycle crashes along urban multilane segments, while collector and local road types were significantly associated with reduced motorcycle crashes along urban two-lane segments.

Conclusions: Countermeasures were then proposed to improve motorcyclists' safety along urban roadways (e.g., installing advance warning signs and/or chevrons along urban roadway segments with sharp horizontal curves).