Winter Highway Operations (2005)

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5This chapter reviews research literature as of 2003 relevant to winter operations to provide a context for understanding advancements in the state of the practice. This limited litera- ture search describes recent articles on key topics related to the report including anti-icing chemicals, Road Weather Information Systems (RWIS), route optimization and auto- matic vehicle location (AVL), environmental and worker health effects, and emerging technologies. They provide insight to the direction research has taken over the surveyed 10 years. A search using Transportation Research Informa- tion Service (TRIS) Online provided hundreds of results, with a limited number of peer-reviewed publications. The first research results described here include the col- laborative efforts between the Colorado DOT and the Col- orado auto insurance industry that indicated a shift toward increasing use of deicing chemicals and the decreasing use of sand (Chang et al. 2002). The specification for sand no larger that 3/8 in. has contributed to a less-than-expected increase in windshield damage costs for the traveling public. The cost basis was arrived at by combining the amount paid out by two insurance companies reflecting 32% of the Colorado auto insurance industry, normalized against the growth in number of automobile policies over 8 years. A study in Iowa concluded that dry abrasives, when applied to the roadway with significant traffic traveling at high speeds, remain in place for approximately 10 to 100 vehicle passages (Nixon 2001). A study by the Center for Transportation Research and Education at Iowa State University presents the primary chal- lenges to winter highway operations (Knapp et al. 2000). One of the findings of the research was that although traffic vol- ume during the study period significantly decreased, from 16% to 47%, hourly crash frequencies and approximate crash rates increased dramatically, on the order of 942%. It also found that in the case of Iowa highways, the number of crashes per storm increases with an increase of any of three variables: (1) a prod- uct of season length and traffic volume in million vehicle miles, (2) snowfall intensity, and (3) maximum wind speed gusts. Also important for winter highway operations is their finding that although the average vehicle speed showed a 16% reduction, the standard deviation for storm speeds was much larger than for nonstorm periods, 7.57 mph versus 1.86 mph. A method for categorizing and ranking various anti-icing chemicals on the basis of performance in a number of cat- egories was produced by the Iowa Institute of Hydraulic Research Hydroscience and Engineering Department at the University of Iowa (Nixon 2002). It defines and uses the cat- egories freezing point depression, consistency, environmen- tal impact, stability, corrosion, handling, conductivity, and documentation to assist in selecting anti-icing chemicals. In a report for the Ohio DOT, recommendations for a statewide expansion of the state’s RWIS network were made based on an extensive literature review, product review, cumulative cost comparison, survey of users and administrators, and site visits (Nixon and Williams 2001). Factors used to determine optimal deployment included distance between existing Envi- ronmental Sensor Stations (ESS) in Ohio and surrounding states, number of declared snow days, and annual amounts of Ohio snowfall. A minimum number of RWIS–ESS sites are determined in addition to already deployed sites to meet basic statewide weather prediction and monitoring needs (Zwahlen et al. 2003). Recommendations were made that (1) installations should be at locations with typical rather than extreme con- ditions and (2) that each county garage be equipped with a small weather station and simple pavement sensor near the station for the purpose of creating a weather conscious cul- ture at the county garage level. A study of the Washington State DOT (WSDOT) “rWeather” discontinued website (renamed and incorpo- rated in the larger WSDOT website) and RWIS use among maintenance personnel found that maintenance personnel did not take full advantage of the increased capabilities offered through RWIS in part because it was not necessary in the use of traditional reactive winter maintenance strategies (Boon and Cluett 2003). Recommendations of requirements for the expansion of RWIS included management commitment and continued investment in equipment reliability, demonstration of forecast credibility, targeted training, and implementation planning. This study also identified the strong value to the long-distance traveler of the weather information provided on the website. A study conducted for the Colorado DOT Research Depart- ment evaluated deicers for chemical contaminants, environ- mental effects, human health effects, corrosion, application rates, performance, cost, and advantages and disadvantages (Fischel 2001). It identified information gaps in the knowl- edge base and conducted a preliminary, qualitative worker health effects study. CHAPTER TWO LITERATURE REVIEW

In a study sponsored by the U.S.DOT, geographic infor- mation systems (GIS) and artificial intelligence techniques were used to develop an intelligent snow removal asset man- agement system (Salim et al. 2002). The system was evalu- ated with a case study on snow removal from state roads in Black Hawk County, Iowa. It used the logical rules and exper- tise of the Iowa DOT’s snow removal experts with a GIS to access and manage road data. The system was used to gen- erate prioritized snowplowing routes in visual format, to optimize the allocation of assets for plowing, and to track materials (e.g., salt and sand). The case study of the system produced an improvement in snowplowing time by 1.9% for moderate snowfall. A pilot study of AVL technology by Virginia concluded that the technology could be used to track winter maintenance operations in a satisfactorily and timely manner (Roosevelt et al. 2002). It cautioned future projects in the importance of good background mapping, such as orthorectified aerial pho- tographs, that lane location determination is impractical, that there exists a limit to the amount of data the system can process, and that repeated installation and removal of the AVL units results in an unacceptable rate of connection and unit break- ages. The study found that although two-way messaging is important, other methods of communications with the opera- tors would be better, and two-way messaging should only be used in case of an emergency. As with most technology, the importance of logistical support was highlighted. The follow- ing common themes associated with successful field imple- mentation of technology were also supported by this study: • Existence of a project champion with desire and resources; • Available and supportive information technology personnel; • Field personnel with ownership in the system, an under- standing of it, and who are supportive of it; and • Identified and developed preventative maintenance pro- cedures and assigned personnel. One of the prominent issues identified was the need for efficient procedures to assign identification numbers to the vehicles and update the computer system as assignments were made or changed. NCHRP Project 6-12 provided a review of existing and proposed concepts for improving visibility for snowplowing operations along with the identification and development of potential means for improving these operations (Rea and Thompson 2000). The project included limited field tests to evaluate the potential benefits of these concepts. Conclusions of the research included the following: • A trap angle of approximately 50° for front plows will reduce the amount of material blown over the plow and onto the windshield. 6 • Packing flaps at the discharge ends of front plows reduce the size of the snow cloud around and behind the snowplow. • Closing the gap between the front plow’s discharge end and the intake end of the wing plow will reduce the size of the snow cloud around and behind the snowplow when wing plows are used. • Side vanes with a 20° angle to the snowplow’s body, mounted on the rear of the vehicle, will reduce snow and ice accumulation on surfaces and on the rear light- ing of the snowplow. • Switching off the driver-side headlamp and using an auxiliary passenger-side headlamp will reduce the back- scattered light seen by the operator during snowfall. • Shielded headlamps, the louvered or cut-off type, that reduce stray light above the horizontal plane, will also reduce backscattered light. • Steady-burning light bars, mounted along the rear edges of the snowplow truck, will improve following drivers’ ability to detect changes in the snowplow vehicle’s speed and will provide an indication of the vehicle’s width. A report for the Virginia DOT indicated potential for heat pipe technology to be used effectively on bridge decks to pre- vent snow and ice accumulation. However, a reliable deck heating system requires further development, including more robust controls (Hoppe 2000). The report also concluded that an active system requires a substantial effort in terms of time, personnel, and expertise to ensure that all components are functioning safely and effectively. Conclusions and recom- mendations included: • It is feasible to apply heat pipe technology to heating bridge decks. • For effective deck heating, selecting a proper working fluid for heat pipes is critical. • The surface condition sensor should be placed on the bridge deck. • The heat pipe system does not pose a construction problem. • Operating costs for the heat pipe system are lower than for an alternate electrical or hydronic system. • The heating system does not appear to have any adverse effects on the durability of the bridge deck. • The use of an infrared camera can be very effective in evaluating heat distribution and intensity across the deck surface. • The failure of a single sensor can cause the entire heat- ing system to become inoperable, making the control system redundant. • Place the control sensor on the bridge deck. • Use infrared scans as a measure of the performance of the heating system before granting final acceptance. There have been cost–benefit analyses done to enable emerging technologies to become part of the mainstream. One study concluded that limited data collection was adequate for

7initial justification; however, data collection methods and research studies have not been applied successfully for oper- ational scale performance measures (Meyer 2002). Many research projects were scheduled to publish their results at approximately the same time this synthesis was under way. There has been significant effort by the AASHTO Snow and Ice Pooled Cooperative Fund Program (SICOP) and the FHWA Road Weather Management Program to keep recently published research relevant to winter highway opera- tions available on the Internet. This effort has resulted in good collections of knowledge-improving papers on their respective websites: http://www.sicop.net/documents.htm (AASHTO) and http://www.ops.fhwa.dot.gov/weather/resources/publica- tions.htm (FHWA). The reader is directed to these to sites for the most current information available. Other documents relevant to winter highway operations are referenced throughout this synthesis and are also found in the literature reference list at the end of this document.