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14 decision makers for winter highway operations throughout the ing their activities. One survey question asked the agencies to world by means of e-mail. The significance of this resource is rank the winter pavement conditions that most effect their imaginable in terms of realizing its potential to completely operations, segregated by urban, suburban, and rural geogra- replace this document in a timely and question-specific man- phy. Frontline maintenance personnel are frequently already ner. All a maintenance manager has to do is pose a question to attuned to issues that are seemingly uncovered in scientific the group such as, "what is the most cost-effective winter oper- analysis of data collected from a more diverse and geographi- ation technology you use and why?," sit back, and wait for the cally dispersed study. It is possible that the description of pri- response from every road weather climate and size of operation mary field operation conditions falls within this category. A extant. somewhat surprising picture of the distribution emerges from the survey results. At a frontline level, blowing and drifting It is important to note that the information is not peer snow may seem like a big problem; however, because it is reviewed other than through each reader's comments, correc- quite location specific, it might not be considered a major prob- tions, or replies to statements made in response to the ques- lem affecting the winter maintenance community as a whole. tions posed; that is, responses must always be put to a rele- vance and correctness test before basing actions on them. Even Rural drifting snow was ranked the number one problem with this caveat, the inquiry and exchange of experience and by 73% of the responding agencies. When the primary and information among this group has enhanced and advanced secondary problem responses are combined, suburban and winter operations at various local levels in an immeasurably rural blowing snow is the most prevalent problem faced by successful manner. Two examples of additional use of the 100% of the agencies. Clearly, blowing snow presents an Internet in making valuable winter operations information arena for improvement in deployment focus and assistance. widely available are the FHWA winter maintenance virtual Tabler's Controlling Blowing and Drifting Snow with Snow clearinghouse and SICOP websites. The Internet has also Fences and Road Design (2003) is a valuable and timely connected the agencies with their customers in a highly cost- update of his earlier 1994 Design Guidelines for the Control efficient and valuable way as will be described later under of Blowing and Drifting Snow. traveler information (see chapter seven). The development of suburban snowpack is a primary con- cern of 71% of the responding agencies. Combining the pri- OPERATIONS mary and secondary problems indicates that rural, suburban, and urban snowpack; suburban black ice; and urban and sub- The discussion of operations is divided into five subtopics: Pri- urban frost are the most significant problems. The results of mary Field Operating Conditions, Equipment, Materials, Tra- this question are presented in graphic format in Figure 4. ditional Activities, and RWIS. Traditional activities include classic methods such as snow removal with truck-mounted When municipalities' answers are separated, they rank plows, maintaining the driving surface during storms, storm development of snowpack and black ice as their primary clean-up, and controlling blowing snow with snow fences. concerns. Primary Field Operation Conditions Equipment Winter maintenance personnel encounter a variety of adverse Equipment includes the communication methods used within pavement conditions that need to be addressed in accomplish- the winter maintenance vehicles, the type of trucks and Urban Suburban Rural 100% 75% 50% 25% 0% ain in in w w w ow w ow st ck t ck ck st ck ck ck Ice Ice Ice s no no no no Ra Ra Fro Fro Fro pa pa pa n n pa gR pa pa gS gS gS gS gS gS ck ck ck ing ing Ice Ice Ice ow ow ow zin Bla Bla Bla iftin iftin iftin win win win ez ez Sn Sn Sn e Fre Fre Fre Blo Blo Blo Dr Dr Dr Primary Problem Secondary Problem Rare No Response FIGURE 4 Problematic winter pavement surface conditions categorized by the regional characteristics.
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15 their components, and the material holding and application to provide data, there were only minor changes in the num- equipment. ber of trucks as categorized by how they are equipped; with only a plow, only a spreader, both a plow and spreader, or all- liquid trucks. Responding agencies with primarily rural main- Communications tenance responsibilities on average own and operate approx- imately 1,000 trucks total. Communications with maintenance trucks is predominately through the use of two-way UHF/VHF and trunk system However, there have been some noteworthy changes in radios. Seven of the respondents (41%) have deployed 800 equipment usage. For example, in Maryland, the fleet of MHz systems. Alberta, Manitoba, Nebraska, Saskatchewan, motorgraders used has more than tripled; whereas, in con- and Washington State cited cellular phones as a method of trast, in other states the use of motorgraders to remove road- communication, with Vancouver relying solely on cellular way ice pack has decreased. There also appears to be a slight technology. increase in use of snowblowers, particularly in rural plains applications. Surprisingly, 45% of the agencies reported significant problems with their communication systems. The most com- There has been a dramatic increase in the use of pavement mon problem is inadequate coverage owing to dead spots temperature sensors on winter maintenance vehicles. In 1994, caused by terrain or a lack of repeaters. Limited channel capac- very few (less than 1%) winter maintenance vehicles had this ity as well as the limited functionality of 800 MHz systems equipment; whereas, an average of 30% of the vehicles had in mountainous terrain were also cited as technological prob- pavement temperature sensors at the time of this synthesis. lems. The drawback associated with cellular communication This trend tends to indicate an increasing effort to provide during emergencies as a result of inadequate capacity was more pavement-specific information to the equipment oper- also mentioned. Logistical problems associated with commu- ator while on task, where it can make the most effective dif- nication to field personnel were also described. These prob- ference in efficiencies. It is important to note that the accu- lems include radios being fixed within the vehicle and there- racy and relevance of the temperature data provided by these fore not useful when crews are outside the truck, and the lack sensors is highly variable and dependent on mounting, use, of interoperability with other agency radio systems. and interpretation. Tabler (2003) provides insight to this prob- lem in the results of a recent study. An important trend is seen in the rise of problems associ- ated with increased on-board computerized systems. Inter- ference by radios with other electronic systems was reported Plow Blade Types by three agencies. Plow blade types include one-way-only, V, and reversible, and can be used on either plow trucks or motorgraders. Some Trucks motorgraders are equipped with more than one blade for snow removal. Reversible-type blades are used on approxi- The common response from agencies in all road weather cli- mately two-thirds of the plow trucks; whereas approximately mate categories indicated the use of a fleet of both two- and one-quarter use one-way-only blades, with the remainder three-axle trucks with a gross vehicle weight range of 25,000 being equipped with V-type blades. Motorgraders in use for to 50,000 lb for snow and ice control. Horsepower ratings for winter maintenance are generally equipped with a plow blade these vehicles range from 250 to 300 for trucks without a plow mounted at the front of the vehicle in addition to the grader wing and from 325 to 400 for those equipped with a wing. blade. More than 60% use reversible blades for plowing snow and approximately 30% use a V-type blade. A handful of state DOTs have initiated concept vehicle projects. Under these efforts new technologies and ideas for The use of wing plows has also increased in rural areas and integrating advanced navigation, surface pavement condi- is somewhat more widespread in Canada than in the United tion, chemical application, driver environments, and others States. The New Brunswick DOT reported that all of its trucks are being tested in actual over-the-road snowplows. It is have been equipped with wing plows for at least 10 years. anticipated that this area will offer the greatest possibility of Maryland use wings with benching capability. advancement in equipment and its operation over the next few years. Alberta, Missouri, and Saskatchewan noted using advance- ments made in their plow designs. Maryland uses rubber Attempts to collect information about changes in the equip- blades on some plows, as does Oregon. Oregon also uses ment that maintenance departments own and use was limited ultra-high molecular weight polymer moldboard plows. One in its success. Many agencies lack resources to effectively improvement based on research is the flush-mounted, carbide research records regarding past operations and were, there- insert at the front edge of the blade and a non-zero clearance fore, unable to provide data. For the agencies that were able angle (Nixon 1993).
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16 Spreaders degree. On average, these systems are used on 40% of the trucks of the responding agencies. Application of solids and liquids requires the interaction of three components: (1) box, bed, hopper, and/or liquid tanks; Computerized controls associated with spreading rates for (2) spinner or nozzles; and (3) application rate controls. both liquids and solids represent a significant change in equip- ment available over the 10 years surveyed. Not surprisingly, The term spreader is used interchangeably in respondent's the use of computerized spreader controls has increased, with answers to mean the box or the distribution spinner, or the 95% of responding agencies reporting increased use. Wide- combination of both. The largest spreader box capacity used spread use started much earlier in Canada then in the United by the responding agencies is 15 cubic yards. The overall aver- States. Computerized spreader controls are typically used on age size of spreaders described was 8 cubic yards. Spreader two-thirds of the winter maintenance vehicles by the organi- box types (hopper, v-box, slide-in, and tailgate) and spinner zations surveyed. locations (rear, behind cab, and underbody) are chosen to fit operational experiences and constraints by all the responding Seventeen of the responding agencies described the use agencies and represent the full range of styles. More than of computerized spreader controls. Montana, Nebraska, and 95% of the agencies that calibrate do so on an annual basis. Nevada indicated that in-cab data collection technologies Several report that calibration is also performed when repairs allow for better control of materials application. The reduction of application rates, better assurance of appropriate amounts, or changes are made to the equipment or material. Indiana and daily availability of data are given as benefits of these indicated that it attempts to accomplish annual calibration, systems. Manitoba was still monitoring the introduction of but that it varies from year to year. Edmonton calibrates both spreader controls and data collection. Indiana commented that monthly and annually. Montana and Oregon responded that acceptance has been slow, but is growing. Key problems expe- they did not calibrate their spreader distribution rates. The rienced by the responding agencies included inadequate min- balance of the respondents have adapted or adopted com- imum capacities of the hydraulic system, too may wires and monly known methods to calibrate their spreaders. Some of connectors, and corrosion problems with wiring connections. these include trust in the settings of the electronically auto- mated settings, verification of settings through catch and mea- sure, and various calculations based on equipment speed, Materials chain speed, spinner revolutions, auger revolutions per minute, correlation to ground or vehicle speed, and physical distance The use of chemicals other than sodium chloride (NaCl), all- versus change in load. liquids, and pre-wetting were the most common change in winter operations over the 10 years surveyed. Specifically, the addition of pre-wetting and all-liquid trucks along with The calculations used in calibration are represented by the inclusion of easier cab controls and ground speed con- Nevada, which has been highly successful using the Salt Insti- trollers for spreader operation were key changes to winter tute's spreader manual calibration sheet provided in The Snow- operations of the survey group. fighter's Handbook (1999) to calibrate older spreaders that make up 20% of their fleet. Abrasives Many agencies reported methods to ensure that spreaders maintain calibration and perform at the desired level. Alberta Every agency that responded reported the use of abrasives; Transportation monitors contractor performance with a spot however, it was clearly indicated that this use is being dis- calibration check of 5% of the units. Others vary among couraged because it is not a deicing agent and requires operator-related methods such as a card kept inside the truck clean-up owing to PM-10 (particulate matter smaller than and turned in, driver judgment based on route length or one 10 micrometers) air quality standards. Other problems expe- of the following metrics: rienced by states including California, Nevada, Oregon, and Washington involve reducing the amount and potential of the · Electronic controls, abrasives entering rivers, negatively affecting the riverbeds. · Weekly maintenance management system validation, Some agencies including California, Edmonton, Nevada, · User information versus data, Oregon, and Washington State, reported that they sweep, · recover, or recycle abrasive materials, particularly in sensi- Random checks, and tive areas. · Third party to the operator. Nebraska indicated that calibration was hard to truly know, Chemicals because operators changed the settings after calibration. The majority of the responding agencies use NaCl in either In 1994, few agencies reported using truck pre-wetter sys- solid or liquid brine form as an anti-icing, deicing, or pre- tems; however, all reported that they now use them to some wetting chemical. The cities of Moncton and Vancouver, as
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17 well as Connecticut and Nova Scotia, use salt as their sole they use the complex chloride containing sodium, potassium, chemical. The northwestern states of Oregon and Montana and magnesium chlorides. The chemical use by reporting do not use road salt at all. agency can be seen in Table 4. For the balance of agencies calcium chloride (CaCl) is the One of the changes that occurred during this 10-year predominant chemical. Six of the 14 agencies specifically period (1994 to 2004) was the formation of groups such as cited use of a corrosion-inhibiting additive. A higher propor- the Pacific Northwest Snowfighters Association (PNSA). This tion of users of magnesium chloride (10 of the 11) specifi- organization of state, province, and municipality highway cally mentioned products with corrosion inhibitors. Alberta, agencies developed specifications leading to a qualified prod- Illinois, and the city of Moncton responded that they apply uct list of snow and ice control chemicals. The specifications corrosion inhibitors to their fleet. Only WSDOT replied that are found on the PNSA website. TABLE 4 ANTI-ICING, DEICING, AND PRE-WETTING CHEMICALS USED BY SURVEYED HIGHWAY AGENCIES NaCl CaCl MgCl Agency Complex Cl CMA Kac NaCl NaCl CaCl MgCl NaCl CaCl MgCl Inhibited Brine Inhibited Inhibited Alberta Transportation California DOT Connecticut DOT City of Edmonton Illinois DOT Indiana DOT Idaho TD ManitobaTransportation & Govt. Services Maryland State Highway Admin. Minnesota DOT Missouri DOT City of Moncton Montana DOT Ministere des Transports du Quebec New Brunswick DOT Nebraska DOT Nova Scotia DOT Nevada DOT Oregon DOT Saskatchewan Highways and Transportation City of Vancouver Washington State DOT Notes: NaCl = sodium chloride; CaCl = calcium chloride; CMA = calcium magnesium acetate; Kac = potassium acetate; MgCl = magnesium chloride.