Comparison of Performance of Solid Salt With Direct Liquid Application of Salt Brine: Vehicle Speed and Pavement Friction

Previous research has not specifically compared friction resulting from salt brine direct liquid application (DLA) to solid salt application. This study sought to fill that gap by conducting field-based experiments with the support of two counties in Wisconsin. One direction of travel on multilane divided roadway segments was treated with salt brine DLA (study route), and the opposite direction was treated with dry solid salt (control route). Field experiments were conducted during 11 winter storms. Performance measures evaluated included vehicular speed, pavement friction (grip), travel disruption (TD), salt used, and time to bare/wet. Mean values from study/control routes and storm conditions were compared to baseline conditions through statistical tests or modeling. Friction measurements were evaluated through mixed-effects meta-regression modeling. The results indicated that friction at the study and control routes was statistically similar; however, salt usage at the study routes with salt brine DLA was between 40% and 72% less than at that control routes with solid salt. Using a limited number of storms, TD at the study routes was found to be between 8% and 39% lower than at the control routes, whereas time to bare/wet (subjective metric) was similar between the study and control routes. Therefore, with the limited data and conditions evaluated, the findings provided some evidence that salt brine DLA and solid salt performed comparably, but salt brine DLA used less salt.