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Safety Effects of Road Weather Information Systems (RWIS) – A Large-Scale Empirical Investigation
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- Author / Creator
- Sharma, Davesh
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In countries like Canada and the United States, where most of the population lives in snowy regions, winter road maintenance (WRM) has become a significant challenge. Hundreds of people are killed, and thousands are injured every year due to inclement winter weather conditions. To combat this, transportation agencies spend a significant amount of their budget on conducting and maintaining WRM activities. Considering their limited budget and resources, it is indispensable to strategize their investments in equipment, labour, and material without jeopardizing commuter safety.
One of the most advanced techniques used for efficient mobilization of WRM services is Road Weather Information Systems (RWIS) - a critical highway intelligent transportation system (ITS) infrastructure. These systems have long been favoured by many North American and European highway authorities as they provide real-time and near-future road condition information collected using roadside sensors during the winter months. Information disseminated by individual RWIS stations is collectively used not only to proficiently organize WRM operations but also to promote safe travel and provide traveller information during adverse weather events. However, the high installation and operational costs of RWIS have necessitated the need to quantify their cost-effectiveness, particularly in improving traffic safety. Limited past efforts have been made to quantify the sole benefits of RWIS, but most analyses were either qualitative in nature or used a naïve safety evaluation technique that resulted in generating less conclusive findings.
Acknowledging the importance of determining their benefits as well as a large gap that exists in current methodologies, this thesis aims to develop a unique methodological framework that can be readily used to evaluate and quantify the sole safety effects of RWIS. In particular, this thesis attempts to tackle and answer two research questions: first, whether implementing RWIS stations reduces winter weather collisions and how much reduction can be expected; second, whether RWIS stations are a cost-effective countermeasure with explicit monetary benefits. These questions were answered by conducting a safety evaluation of RWIS stations and an economic analysis. Safety evaluation of RWIS stations was conducted by using one of the most established and statistically defendable methods used in traffic safety studies, namely, the before-and-after Empirical Bayes (EB) approach was used to perform safety evaluation of RWIS stations. A methodology was developed, and a state-wide investigation of RWIS stations in the state of Iowa was conducted. Geographic Information Science (GIS) based techniques were used for the preparation of intensive geospatial datasets required for calibration and validation of safety performance function (SPF). Furthermore, Yearly Calibration Factors (YCFs) were also locally calibrated using large-scale spatial data, where network-based service area analysis using GIS played a crucial role in selecting treatment and reference sites. The results of safety evaluation were used to conduct a detailed economic analysis and Benefit-to-Cost ratios (BCRs) were estimated as a parameter to assess the economic viability of RWIS stations. One-time installation cost, operations cost, and up-gradation cost for each RWIS station were compared with the monetary value safety benefits.
Utilizing the developed methodology in this thesis, the sole effectiveness of implementing RWIS was quantified to establish RWIS as a safety countermeasure. The findings from the case study showed safety effectiveness of RWIS that ranged from 31.53% to 88.23%, whereby implying that a significant portion of winter weather collisions was reduced after RWIS implementation. The BCRs of the stations ranged from 7.51 to 34.16, indicating a significant amount of safety benefits compared to the cost of RWIS. The research findings suggest that RWIS stations are an economically viable safety countermeasure, and that transportation professionals and highway authorities can now make more informed decisions on furthering RWIS implementations to improve the safety and mobility of the winter traveling public.
The main contributions of this thesis are three-fold. First, the safety effectiveness of RWIS stations was quantified for the first time in the literature using the state-of-the-art EB method with large-scale and multi-year datasets. Second, SPF was locally developed during the process, which is transferable and can be readily used for safety investigations at regions with similar geographical and weather characteristics. Finally, the economic viability of RWIS was quantified using a formal economic analysis at high granularity, which has been absent from the RWIS literature. -
- Graduation date
- Spring 2022
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- 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.