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18 All-Liquid equipment, materials, and technologies such as snowplows, sanders, snowblowers, motorgraders, front-end loaders, salt, The average all-liquid truck capacity is 1,700 gal. Missouri grit, and two-way radios. What were emerging technologies uses both the largest maximum size of 6,000 gal and largest 10 to 20 years ago (e.g., snow fences and RWIS) are now average size of 5,000 gal. Idaho and Nevada also use larger reported as traditional uses by a majority of agencies. than average size all-liquid trucks, reflecting their successes in incorporating all-liquid methods in their snow and ice control activities. The efficiency of large all-liquid trucks is Snow Fences championed by Missouri, which reported that one 5,000-gal tanker replaces two or three dump trucks with small tanks. Seventeen of 20 agencies reported using snow fences. Approx- Minnesota provided application rates, the highest at 1,200 gal imately equal numbers of agencies reported using temporary, per lane mile, with an average rate of 300 gal per lane mile. fixed, and living snow fences (e.g., tree or shrub hedges). Some highway organizations use snow fences extensively, with liv- The manner in which all-liquids are applied has changed ing snow fences becoming increasingly popular. Examples over the surveyed 10 years for 70% of the agencies. Nevada include Oregon, which reports 30 mi (48.3 km) of roadway did not use all-liquid methodology before 1994 and Alberta centerline protected by fixed snow fencing; New Brunswick, deployed this technology in 2001. Improved technology has which reports 6.2 mi (10 km) of roadway centerline protected been a major change in this treatment strategy, greatly increas- by living snow fencing; and Alberta Transportation, which ing the accuracy of application. All-liquid methods have been driven by needs to reduce salt use, environmental con- reports a total of 237 mi (381 km) of cumulative snow fencing cerns, and economic constraints. They have also been driven with all types combined. Only 41% of the responding agencies by the desire for increased LOS. The inclusion and success that use snow fences reported having an annual maintenance of on-board pre-wetting of abrasives or chemicals has also and repair plan and budget for snow fencing. prompted increased reliance on liquids. Enhancing this and representing a significant change is the need for increased experience and training. Other Blowing Snow Control Methods The Montana DOT serves as a unique example of an agency The WSDOT has installed and tested vortex generators, orig- that has made changes in their application of all liquids. The inally designed to keep Antarctic runways free of drifting state has transitioned to a just-in-time response to storm con- snow, on segments of Washington highways in efforts to ditions. They wait for a 100% assurance that a storm event will alleviate drifting snow in the winter and drifting sand year actually occur before all-liquid application, rather than basing round. Caltrans has installed jet roofs on ridgelines above their decision on a forecast. This approach is a result of efforts selected highways to alter the wind flow and reduce the to reduce waste, avoid extra costs, eliminate unnecessary vehi- development of avalanche hazard. cle exposure to corrosion, and improve public relations. Preliminary research on slippery conditions caused by ROAD WEATHER INFORMATION SYSTEMS all-liquid applications has occurred during recent years with nondefinitive findings; however, it was suggested to monitor Use of RWIS has become a mainstream technological incoming humidity levels, especially during the fall season methodology in the winter operations toolbox. In 1994, the (Leggett 1999). All-liquid applications can yield good results; use of RWIS was fairly widespread geographically; how- however, it is not as forgiving as traditional application of ever, it has become an even more essential component to solids. The recommendation of the early research suggests winter operations and is increasingly used by traffic opera- that combining such humidity monitoring with prudent appli- tions. RWIS is multi-faceted, owing to its electronic nature, cation rate and frequency should reduce the likelihood of this communication methods, integration requirements, and road- problem occurring. Oregon began a research project in 2003, side geographical deployment. This is evident in the various focusing on the reduced skid resistance caused by anti-icing divisions within DOTs responsible for operation and mainte- applications. A survey question attempted to ascertain the nance of their systems. Often the responsibility is divided general level of awareness of this issue and need for further between operation or use groups and support or system main- research. More than 31% of the agencies responded that they tenance. Support is most often accomplished at the headquar- did not feel that adequate information was available to avoid ters or regional communications, electronics, or ITS levels. unintended consequences of all-liquid applications. Central support is also a common source for server responsi- bility. Operation of the system is predominately at the district TRADITIONAL TECHNOLOGIES maintenance level. Vendor support and federal government (Canada) support are also cited in two instances (Indiana and There are several winter maintenance operations that can be Moncton) as the parties responsible for maintenance and oper- considered traditional activities including the use of various ation of the system.

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19 Deployment pavement temperature sensors as their primary access to road weather information. Most agencies own and operate the majority of their auto- mated weather stations. However, Washington State relies on a far greater overall number of stations at 430 than any Road Weather Forecasts other agency for which data were collected. Of these, 75% All of the responding agencies provide access to weather are owned by entities other than the WSDOT. Idaho simi- forecasts for the individual winter operations decision maker. larly makes use of a significant number of weather stations The most common access is simply the Internet. The cases that it does not own. These two agencies have proven the where agencies responded otherwise were Canadian munic- usefulness and benefits of exchanging weather data with other ipalities, which follow fairly rigid organization of winter oper- parties. ation efforts; that is, policy, plow routes, etc. However, infor- mation access and adaptability at the operator level is good. Eighty-two percent of those agencies that use automated The respondents use a mix of general forecasts (e.g., National weather stations incorporate pavement sensors with at least Weather Service, Weather Channel, and Meteorologix), fed- some of the stations. Some agencies use more than one erally provided tailored forecasts (e.g., Environment Canada), pavement sensor at a single automated weather station. Nine and consultant highway meteorology firms (e.g., Meridian, of the responding agencies currently use National Transpor- Northwest Weathernet, and Surface Systems Inc.) No ques- tation Communications for ITS Protocol (NTCIP) for ESS. tion specifically asked about the use of pavement tempera- There are many remote deployment issues that the agencies ture forecasts. face including power, communication costs, and impacts to maintenance costs owing to travel distances for centrally based Advancements electronics personnel. The agencies were asked how their use of weather informa- Although increased use and expansion of RWIS are tion and deployment of roadside weather stations has changed described as significant changes in the way winter operations over the period from 1994 to 2004. Fifteen agencies indicated are conducted, 50% of the responding agencies have no that deployments have increased. For example, Nevada went deployment strategy or criteria for locating RWIS sites. Idaho, from no stations in 1994 to 47 in 2003 and Washington State Indiana, Minnesota, Oregon, and Nova Scotia responded from a dozen to more than 65. Montana deployed all of its positively in this regard. In addition, Alberta, New Bruns- sites during the first half of the 10-year period. wick, and Washington State indicated that this was an effort currently under development or in the preliminary stages. Increased resolution and reliance on highway meteorology Nebraska presently deploys only to trouble spots, rather than consultant weather forecasts provided by a surface transporta- to provide a more comprehensive picture of weather data. In tion weather information service was cited by three agencies. 2003, two federally funded projects were begun with regard to siting standards and pavement sensor calibration. During the late summer of 2003, Transport Canada announced a federal initiative toward development of a national RWIS. Federal subsidy through ITS funding within their Strategic Highway Infrastructure Program is designed Information Access to support deployment of RWISESS and the nationwide Seventeen of 22 reporting agencies provided first-hand access integration of all sites, including the existing 150, to provide consistent information to all jurisdictions. to roadside weather information and pavement surface con- ditions for the individual winter operations decision mak- Only two of the agencies (Quebec and Saskatchewan) did ers. The individual winter operations decision maker does not have some remote weather sensors in place in 1994 and not have access to roadside weather and pavement infor- just began deployment of RWIS systems during the follow- mation from RWISESS in two of the municipalities, three ing 10 years. For three others, no significant change other provinces, and one state. This appears to be the exception, than wider use has occurred over that period. Some of the because of the 16, more than three-quarters use some com- changes cited by the agencies included: bination of agency systems and vendor support to provide this access by means of the Internet or on an internal More informed decision making, agency-owned network. In Oregon, the ITS unit is working Use of the data with training, to standardize access to road weather information to appro- Availability of data at more levels, priate personnel. There are several particular cases where Greater numbers of roadside installations, and the information is available only on the agency intranet or Movement toward statewide networks. at a single workstation. Indiana was in the process of deploy- ing an RWIS at the time of the survey. Edmonton and New One of the most significant changes has taken place in Brunswick reported the use of vehicle-mounted infrared Montana where, currently, winter maintenance activities such

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20 as anti-icing do not occur until actual conditions change, Integrating separate systems; rather than being based on a weather forecast. Increased use Improving data displays and simplifying use; and reliance on pavement temperatures obtained from truck- Including supplementary weather information such as mounted sensors not available 10 years ago is a change NEXRAD (Next Generation Radar, which can mea- described by several agencies. sure both precipitation and wind), satellite images, and weather maps; A 2-year study of the Wyoming RWIS, published in 1998, Making RWIS data and weather information directly indicated that the system would facilitate and improve main- accessible in every maintenance station; tenance operations and enhance the safety and convenience Improving site selection procedures; of highway travel if certain critical improvements were made Providing additional training of maintenance staff; (Tabler 1998). Without these improvements, benefits were Providing high-quality weather forecasting services; expected to be marginal and continued operation might not Determining adequate sensor selection for recognition be cost-effective. Key areas identified for improvement that of blowing snow conditions; and have cross-agency relevance included the following: Dedicating personnel to manage and maintain the system.