Winter Maintenance

This project evaluated the feasibility of using friction indicators as tools for improving winter maintenance operations and mobility. It was found that the use of friction measurements for this purpose is feasible (especially when deceleration devices are used), but devices with an extra wheel may not represent a practical solution to friction measurement. The use of such devices works well for runways, where one vehicle is sufficient for an airport, but would not work well for highways where many vehicles equipped with an extra wheel would be needed for successful operational use in winter highway maintenance. Therefore, direct friction measurements may not be a viable operational tool in winter maintenance (although they will and should be used as research tools). Since traction control systems appear to be the only way to eliminate the extra wheel used in current devices, and since their use to predict road surface condition has a great potential for enhancing winter maintenance operations, they should be further investigated. However, if such technology is considered, it has to be automated to ensure that traction applied is beyond the point of slip, thereby eliminating the effect of the traction applied by the driver. Another feasible approach, used by Japan, is to develop models based on climate, traffic, and pavement related data to predict road surface condition. Such indirect measurements have a strong potential for being an operational tool. Two proposed scenarios appear to be promising and practical for improving winter maintenance operations, safety, and mobility. One scenario suggests the use of friction measurements or indices to provide information to support winter maintenance decision-making qualitatively and in a simple way. It is recommended for operational trial by state departments of transportation at one or more sites. The other scenario relies on the transmittal of friction measurements or indices and locations in near-real-time from the winter maintenance patrol or snowplow/spreader vehicles to a central office where the information is processed and transmitted to users. This scenario requires technology development and integration prior to use. A two-phase follow-up study is recommended to validate both scenarios.

Intelligent winter maintenance vehicles are equipped with automatic vehicle location (AVL) technology, including differential Global Positioning System (DGPS) receivers and various additional sensors that collect equipment status and material use data. DGPS data points are associated with the nearest roadway centerline by calculating minimum perpendicular distances between each roadway centerline representation and the DGPS data points. Highly accurate roadway centerline maps and DGPS measurements are not always available. Thus, spatial mismatches may occur at converging and diverging roadways, divided highways, and intersections. Decision makers use winter maintenance performance measures to evaluate achievement of goals and objectives and to improve winter maintenance operations in public agencies. These performance measures are sensitive to spatial mismatches, which need to be resolved before calculations are done. This paper presents a simple map-matching algorithm that resolves spatial ambiguities by determining the correct roadway centerline on which the vehicle is traveling. The algorithm computes shortest paths between snapped DGPS data points using network topology and turn restrictions. A path is considered viable, and locations for the snapped DGPS data points correct, if similarity exists between values of calculated and recorded vehicle speeds. If a path is not feasible, DGPS points are snapped to alternative roadway centerlines contained within their buffers, shortest paths are recalculated, and speeds are again compared. Examples are presented to illustrate the implementation and effectiveness of the algorithm.

The objective of this study is to investigate and evaluate the effects of weather information (in terms of accuracy and frequency of usage) on winter maintenance costs. To this end, a general winter maintenance cost model is presented, and then a methodology combining sensitivity analysis and neural network methods is proposed. Sensitivity analysis is used to identify the key input variables that significantly affect the output variable. The proposed method and cost model are applied to a case study of the Iowa winter maintenance operations. The results from the case study show that the lane miles of roadway maintained by maintenance units have the most important impact on winter maintenance costs; also, the increased use and accuracy of weather information can reduce costs. Finally, a benefit–cost analysis shows that the use of accurate weather information is a promising way to reduce winter maintenance costs.

AbstractThis study presents the findings from research conducted at the University of New Hampshire Stormwater Center (UNHSC) which investigated porous pavements as a potential strategy for minimizing the use of deicing chemicals for winter maintenance. In cold regions, chloride is an integral component of winter maintenance and safe usage of transportation surfaces. Chloride-laden runoff from impervious surfaces threatens aquatic habitats, degrades drinking water supplies, and corrodes infrastructure. State and federal environmental agencies are beginning to regulate chloride usage through the implementation of total maximum daily loads (TMDLs). Parking surfaces in some watershed studies have been shown to be the single largest chloride source in storm-water runoff, in some instances contributing up to 50% of the total load. This study examined winter maintenance over two winters and 38 storms from 2006–2008. The study evaluated winter performance in response to deicing practices by measuring skid resist...

Surface transportation in the United States is continuously affected by adverse weather conditions, which contribute to thousands of highway fatalities and billions of dollars in economic loss every year. Winter weather has its own peculiar challenges, to which transportation agencies respond through winter maintenance operations. Recent trends toward proactive winter maintenance operations have placed a premium on the value of timely and accurate weather information that reflects current and forecast conditions in the roadway environment. However, few studies have sought to quantify this value and compare it to the costs of obtaining such customized weather information. The Utah Department of Transportation (DOT) implemented a weather operations program that assists the agency's operations, maintenance, and construction functions by providing detailed, often customized, area-specific weather forecasts. This program's genesis provides a useful case study to quantify the cost-effectiveness of weather information. Described is the application of an artificial neural network model using winter maintenance cost data from dozens of Utah DOT maintenance sheds for the 2004 to 2005 winter to estimate the cost-effectiveness of this program. The model estimated the value and additional saving potential of the Utah DOT weather service to be 11% to 25% and 4% to 10% of the Utah DOT labor and materials cost for winter maintenance, respectively. On the basis of the program's cost, the benefit-cost ratio was calculated at over 11:1. The results highlight the potential benefits that may be realized by an agency using improved weather information to direct its winter maintenance activities.

The goal of this research project was to develop a method to measure the performance of a winter maintenance program with respect to the task of providing safety and mobility to the travelling public. Developing these measures required a number of steps, each of which was accomplished. First, the impact of winter weather on safety (crash rates) and mobility (average vehicle speeds) was measured by a combination of literature reviews and analysis of Iowa Department of Transportation traffic and Road Weather Information System data. Second, because not all winter storms are the same in their effects on safety and mobility, a method had to be developed to determine how much the various factors that describe a winter storm actually change safety and mobility. As part of this effort a storm severity index was developed, which ranks each winter storm on a scale between 0 (a very benign storm) and 1 (the worst imaginable storm). Additionally a number of methods of modeling the relationships between weather, winter maintenance actions and road surface conditions were developed and tested. The end result of this study was a performance measure based on average vehicle speed. For a given class of road, a maximum expected average speed reduction has been identified. For a given storm, this maximum expected average speed reduction is modified by the storm severity index to give a target average speed reduction. Thus, if for a given road the maximum expected average speed reduction is 20 mph, and the storm severity for a particular storm is 0.6, then the target average speed reduction for that road in that storm is 0.6 x 20 mph or 12 mph. If the average speed on that road during and after the storm is only 12 mph or less than the average speed on that road in good weather conditions, then the winter maintenance performance goal has been met.

The need to objectively evaluate the effect of new technology and the advent of externally contracted winter maintenance have increased the need for quantitative measures of winter maintenance efficiency and effectiveness. Varying severity of winter storms and lane kilometers within a maintenance facility’s service area together largely account for storm-to-storm differences in the cost of fighting snow. Efforts were made to develop a measure of winter maintenance efficiency that accounts for labor, equipment, and material costs, as well as storm severity and duration, for an established number of lane kilometers of given service levels. The expenditures are normalized by the lane kilometers in the maintenance facility’s service area and a storm severity index. The storm severity index (WI) is a modified winter index calculated from weighted daily snowfall totals and minimum and maximum temperatures. The resulting winter maintenance metric (daily snow-fighting $/WI × lane-km) is a normalized measure of a maintenance facility’s efficiency in performing snow- and ice-control operations. Databases and resulting winter maintenance efficiency metrics were developed for the winters 1996–1997, 1997–1998, and 1999–2000 for three Utah Department of Transportation maintenance facilities. The efficiency of these three sheds is compared for the winter of 1996–1997, and the winter maintenance efficiency is considered at one shed for specific storms during winter 1998–1999. The winter maintenance efficiency metric allows maintenance managers to objectively consider storm-to-storm efficiency within a facility and to compare the storm-to-storm and annual efficiency of facilities. The impact of new technology on winter maintenance and the efficiency with which contract organizations perform snow-fighting duties can be measured with a winter maintenance metric.

It is intuitively obvious that snow or ice on a road surface will make that surface more slippery and thus more hazardous. However, quantifying this slipperiness by measuring the friction between the road surface and a vehicle is rather difficult. If such friction readings could be easily made, they might provide a means to control winter maintenance activities more efficiently than at present. This study is a preliminary examination of the possibility of using friction as an operational tool in winter maintenance. In particular, the relationship of friction to traffic volume and speed, and accident rates is examined, and the current lack of knowledge in this area is outlined. The state of the art of friction measuring techniques is reviewed A series of experiments whereby greater knowledge of how friction deteriorates during a stonn and is restored by treatment is proposed. The relationship between plowing forces and the ice-pavement bond strength is discussed. The challenge of integrating all these potential sources of infonnation into a useful final product is presented together with a potential approach. A preliminary cost-benefit analysis of friction measuring devices is perfonned and suggests that considerable savings might be realized if certain assumptions should hold true. The steps required to bring friction from its current state as a research tool to full deployment as an operational tool are presented and discussed. While much remains to be done in this regard, it is apparent that friction could be an extremely effective operational tool in winter maintenance activities of the future.

Chloride-based chemicals, known as road salts, play a key role in ensuring safe winter-driving conditions, especially for highways enduring cold and snowy weather. They are widely applied for anti-icing, deicing, and pre-wetting operations. Traditionally, nominal cost and effectiveness are the major criteria when the Department of Transportation professionals select the chemicals for snow and ice control. However, there are growing concerns over negative impacts that road salts pose on motor vehicles, the transportation infrastructure, and the environment. The corrosion and environmental costs pertinent to road salts amount up to at least $469 per ton on average, and they are often ignored in formulating highway winter maintenance strategies. The magnitude of such hidden costs is significant compared with the nominal cost of using road salts for snow and ice control (approximately three times). Some products for snow and ice control may cost less in regard to materials, labor and equipment, but cost more in the long run as a result of their corrosion and environmental impacts. Therefore, an asset management perspective should be utilized to ensure that any cost savings of winter maintenance practices would not be at the price of deteriorated infrastructure, impaired environment, or jeopardized traveler safety. The crux is to strike the right balance in meeting multiple goals of the highway agency, including safety, mobility, environmental stewardship, infrastructure preservation, and economics. Considerable amount of research is still needed in order to fill the knowledge gap and establish a scientifically robust, defensible decision-making process for highway winter maintenance.

The improved ride quality and other possible safety benefits associated with New Generation Open-Graded Friction Course (NGOGFC) or Permeable Friction Course (PFC) pavements—better friction, lower noise, less splash and spray, higher visibility, reduced hydroplaning, and reduced nighttime surface glare in wet weather conditions—have made them highly attractive to engineers and contractors in the last 3 decades. Nevertheless, the durability problems and performance and maintenance issues exhibited by NGOGFCs under winter weather conditions, especially the fast formation of black ice, have prevented their widespread use. Recent research has investigated new preventive methods and materials for handling these winter maintenance issues and improving durability in NGOGFCs. In 2005, the Center for Transportation Research (CTR) conducted an online survey of different districts within the Texas Department of Transportation (TxDOT) to gather information on NGOGFCs, and in 2004–2005 CTR conducted lab and field experiments to test the methodology for detecting black ice formation on NGOGFCs. This report presents the findings of the CTR survey results and research.