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Assessing the Effects of Snow and Ice Control Operations: The Interdependency between Weather Variables, Maintenance Operations, Pavement Friction, and Collisions
- Author / Creator
- Abohassan, Ahmed
An effective winter road maintenance (WRM) program is essential for cities that face severe winter conditions. Snowstorms create slippery road surface conditions (RSC) that disrupt traffic flows and endanger motorists. To combat this, municipalities use a variety of tools to improve the driving conditions such as applying anti-icing agents before snowstorms, de-icing and snow plowing operations during and after snowstorms. Although these tools are common, the degree to which they improve RSC and traffic safety is an area that has not yet been fully investigated. In this thesis, a safety assessment of achieving bare pavement conditions is studied by examining the interconnection between a multitude of key influencing factors including weather variables, maintenance operations, pavement frictions, and collision frequency in the event of a snowstorm. The primary objectives of this study were to better understand the roles of maintenance operations in improving winter road safety and restoring bare pavement after snowstorms. These objectives were achieved by employing a location-specific and event-based framework to investigate the impacts of the different weather variables as well as maintenance operations on pavement friction and collision counts during snowstorms in urban environments.
Using multi-linear regression, it was shown that the total precipitation during snowstorms, extremely low temperatures, and the potential for black-ice formation all have a negative consequence on pavement friction. By comparison, snowplowing operations, application of anti-icing agents, and the frequency of de-icing operations all have positive effects on improving pavement friction.
Another important relationship explored was how pavement friction affected collision frequency, and for this, Negative Binomial regression models were used. The results of this investigation highlighted three ranges of pavement friction coefficients: pavement friction above 0.6, which led to a significant reduction in collisions, pavement friction between 0.6 and 0.35, which had an insignificant reduction in collisions, and pavement friction below 0.35 that resulted in a significant increase in collisions. Furthermore, arterial roads were found to experience more collisions compared to collector roads which could possibly be attributed to their profoundly varying road characteristics such as higher traffic volumes, higher speed limits, and the difference in drivers’ behavior while traveling on them.
After establishing that the pavement friction coefficient “G” can be explained using weather and maintenance operations data, and that pavement friction is a significant factor in influencing collisions during snowstorms, structural equation modeling (SEM) was used to simultaneously model the two relationships in one framework. By using pavement friction as a mediating variable, the indirect influences of the independent variables on road safety were identified. The findings suggest that precipitation, extremely low temperatures, and black-ice potentials all had indirect but significant negative effects on road safety. On the contrary, snowplowing and anti-icing operations were shown to have significantly improved road safety indirectly.
The SEM model developed was used to demonstrate its key features by applying it to a hypothetical snowstorm scenario. The results of the analysis indicate that applying anti-icing agents onto roads before snowstorms could result in a 14% reduction in collisions, snowplowing operations can reduce collisions by 33%, and by combining the two tools together collisions can be reduced by up to 42%. These reductions in collisions can further increase exponentially with higher traffic exposure.
The models developed and findings demonstrated in this thesis can help transportation agencies make more informed and timely decisions to reduce winter weather-related collisions while maximizing the efficacy of existing WRM services and resources.
- Graduation date
- Fall 2021
- Type of Item
- Master of Science
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.