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

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

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