Executive Summary

Weather significantly affects the safety and capacity of the nation’s roadways. Adverse weather is associated with over 1.5 million vehicular accidents each year, accounting for approximately 800,000 injuries and 7,000 fatalities. Poor road or visibility conditions often cause drivers to slow down, thereby substantially reducing roadway capacity, increasing travel times, and in some cases contributing to chain-reaction accidents. It is estimated that drivers endure over 500 million hours of delay annually on the nation’s highways and principle arterial roads because of fog, snow, and ice. This conservative estimate does not account for considerable delay due to rain and wet pavement. Because little new highway capacity will be built in the coming decades and vehicle miles traveled are projected to continue increasing, it is likely that maintaining the safety and capacity of the nation’s roadways will continue to be a challenge in the foreseeable future.

An improved strategy for addressing the impacts of weather on surface transportation has the potential to help mitigate roadway congestion and save lives. High-quality weather observations and forecasts specific to the roadway environment could help users, including drivers, fleet dispatchers, and law enforcement and emergency management personnel, make better decisions, thereby increasing travel efficiency and safety during adverse weather conditions. Improved road weather information could also help those who construct, operate, and maintain the roadways to better respond to weather problems. More globally, addressing road weather issues could help position the nation’s road transportation system to respond appropriately to anticipated major changes in demographics and technology of the twenty-first century.

Despite the advantages of providing enhanced weather information to multiple users, such services have yet to be widely implemented. This reflects a lack of coordination of existing resources and knowledge, as well as a historical shortage of research and development efforts focused on road



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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Executive Summary Weather significantly affects the safety and capacity of the nation’s roadways. Adverse weather is associated with over 1.5 million vehicular accidents each year, accounting for approximately 800,000 injuries and 7,000 fatalities. Poor road or visibility conditions often cause drivers to slow down, thereby substantially reducing roadway capacity, increasing travel times, and in some cases contributing to chain-reaction accidents. It is estimated that drivers endure over 500 million hours of delay annually on the nation’s highways and principle arterial roads because of fog, snow, and ice. This conservative estimate does not account for considerable delay due to rain and wet pavement. Because little new highway capacity will be built in the coming decades and vehicle miles traveled are projected to continue increasing, it is likely that maintaining the safety and capacity of the nation’s roadways will continue to be a challenge in the foreseeable future. An improved strategy for addressing the impacts of weather on surface transportation has the potential to help mitigate roadway congestion and save lives. High-quality weather observations and forecasts specific to the roadway environment could help users, including drivers, fleet dispatchers, and law enforcement and emergency management personnel, make better decisions, thereby increasing travel efficiency and safety during adverse weather conditions. Improved road weather information could also help those who construct, operate, and maintain the roadways to better respond to weather problems. More globally, addressing road weather issues could help position the nation’s road transportation system to respond appropriately to anticipated major changes in demographics and technology of the twenty-first century. Despite the advantages of providing enhanced weather information to multiple users, such services have yet to be widely implemented. This reflects a lack of coordination of existing resources and knowledge, as well as a historical shortage of research and development efforts focused on road

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services weather. Further, the development of improved capabilities to provide road weather information has been hindered by a lack of interaction between meteorologists and transportation researchers as well as insufficient funding specifically directed at the road weather problem. Recent and anticipated advances make the field of road weather ripe for significant progress in understanding and capability. Accompanying advances in meteorology and transportation are improvements in communications, computational capabilities, and geographic information systems, all of which have clear applications to the road weather problem. The notion of smart vehicles in constant communication with weather information providers and traffic control centers, commercial fleets constantly adjusting their routing to avoid anticipated storms, and road maintenance personnel being guided continuously by telemetered in-road sensors no longer needs to be limited to the realm of science fiction. The Committee on Weather Research for Surface Transportation was formed at the request of the Federal Highway Administration to investigate the current state of knowledge regarding road weather conditions and to recommend key areas of research to enhance operational production of weather-related information for roads (see Appendix A for the full statement of task). The committee’s findings and recommendations are designed to provide a framework to engage the transportation and weather communities, along with other stakeholders, to help shape and guide a focused road weather research program. The recommendations will help the weather and transportation research and operations communities capitalize on existing capabilities and take advantage of opportunities for advances. They include a suite of research activities as well as efforts to foster the implementation of an operational road weather capability. OVERARCHING RECOMMENDATION 1. Establish a focused, coordinated national road weather research program. The committee finds that there are substantial research questions and opportunities in road weather that warrant a long-term national commitment and therefore recommends the establishment of a focused, coordinated national road weather research program. Sufficient knowledge and experience exist today to initiate such a program; however, some aspects of the program will require additional research and experience before they can be completely defined and implemented. A road weather research

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services program is timely in that it can take advantage of investments being made in weather and transportation research and infrastructure. An incremental investment in integrating and extending these efforts will reap substantial benefits by producing a national road weather information system as part of the nation’s emerging infostructure—a network of data collection and dissemination necessary to support real-time management and operation of the roadway transportation system. Goals of the Program The goals of the recommended national road weather research program should be to (1) maximize the use of available road weather information and technologies; (2) expand road weather research and development to enhance roadway safety, capacity, and efficiency while minimizing environmental impacts; and (3) effectively implement new scientific and technological advances. Program Implementation These goals should be attained by establishing regional centers, national demonstration corridors, and a nationwide solicitation to support individual investigator-led research projects. It is essential that the program foster close, continuing interaction between the research community and those who will use the research results to ensure that users’ needs are well integrated into all stages of the research and development process. Indeed, the private sector can serve as an important conduit for transferring research results to operations. In all cases the program must be guided by careful cost-benefit analyses. The committee recommends regional research centers to develop new technologies, foster technology implementation on regional roadways, and facilitate interaction among federal, state, and local governments, the private sector, and academia. Such centers could be an attractive alternative to establishing individual state programs because many states in a particular region share the same road weather challenges. These regional centers should be interdisciplinary, incorporating weather and transportation researchers as well as relevant practitioners in the public and private sectors. It is essential that the centers be funded competitively with due consideration given to reflect different weather conditions and transportation problems common to their regions. In addition to addressing the needs of their regions, individual centers should specialize to avoid redundant research

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services on the road weather challenges that are multiregional or even national in scale. For example, one center could specialize in fog as a visibility impediment (a national problem), while another could specialize in evacuation strategies (a problem affecting hurricane-prone regions). Because regional research centers may require substantial investment in infrastructure before research can be conducted, the center selection should consider other collocated resources, such as computing centers or strong university research programs, that could be leveraged. An alternative to regional centers that avoids some of these initial costs is technology development teams, for which researchers are selected competitively from various research centers to work together on a specific research and development problem. This concept has been used successfully by the Federal Aviation Administration’s Aviation Weather Research Program to provide efficient and flexible operationally relevant research results. If the technology development team approach is chosen, then strong and effective linkages to the private sector need to be built into the team structure. The committee also recommends national corridors along two U.S. interstate highways, one running north-south and one running east-west, to demonstrate the effectiveness of various road weather improvements, facilitate nationwide implementation of research results, and provide a seamless stream of road weather information to users. Ideally, the selected highways would traverse several climate zones containing varied land cover, use, and terrain. Further, they would pass through several states that are early adopters of Intelligent Transportation System (ITS) technology and are agreeable to serving as leading states in the implementation of the national road weather research program. Special programs should be established for the federal government and the private sector to partner with these states to showcase road weather products and services. Many of the recommendations made in this report for new technology should be implemented first along these corridors. Program Management and Funding Transportation research and management are currently highly decentralized, largely implemented by states, and meteorological research and operations are spread across several federal agencies, universities, and research centers. The private sector has provided many of the targeted road weather services to date. Yet, for the proposed road weather research program to succeed, centralized leadership at the federal level is essential in setting research priorities, administering grants, providing a central reposi-

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services tory for research findings, ensuring accountability, and fostering the transfer of new knowledge and technology to operational practice. The Federal Aviation Administration’s Aviation Weather Research Program provides a good model for the federal leadership needed for a road weather research program. The committee recommends that the Federal Highway Administration have the leading role in the national road weather research program and that the National Oceanic and Atmospheric Administration be a lead partner in this effort. The federal government should establish an interagency coordinating council to guide the national road weather research program. In addition to the Federal Highway Administration, participation on this council should include at a minimum the National Oceanic and Atmospheric Administration and the National Science Foundation, especially through their joint U.S. Weather Research Program. It is no less critical that the leadership of the proposed road weather research program foster effective partnerships with the private sector in a manner that provides clear processes for interaction. The committee recommends that long-term, dedicated funding for road weather research sufficient to achieve the program’s goals be established as new funding in the Federal Highway Administration. The committee estimates that the research program will require a minimum of $25 million per year, based on an assessment of unmet needs, the capacity of the research community to conduct the program effectively, and costs for comparable transportation research initiatives in other areas, such as the Aviation Weather Research Program. The committee believes that many of the research and development challenges that it has identified will require more than a decade to solve; thus a long-term research and development program with appropriate funding commitments is required. Although the Federal Highway Administration is recommended as the primary funding recipient, the committee feels that the dedicated funds for this program will be highly leveraged with funds focused on other initiatives that have an affinity with road weather research and development. Steps should also be taken to foster effective public-private-academic partnerships in road weather research and technology implementation. Essential partners in this effort include the Federal Highway Administration, the National Oceanic and Atmospheric Administration, the National Science Foundation, the American Association of State Highway and Transportation Officials (AASHTO), academia, state and local governments, the private sector, and nongovernmental organizations such as ITS America and the American Meteorological Society. The committee believes that the preceding recommendations concerning regional research centers, a focus on

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services national demonstration corridors, and widely accessible databases will facilitate such partnerships. Indeed, the contributions from all sectors are essential for the implementation of the program recommended here. Research Framework The proposed road weather research program should support research and development in the following five areas: a robust, integrated observational network and data management system specifically designed to meet the need for enhanced road weather research and operational capabilities; a coordinated research effort to increase understanding of road weather phenomena and options for increasing safety, mobility, and efficiency of the nation’s roadways during all types of weather; improved modeling capabilities and forecast tools designed to provide relevant, useful information to those who build, manage, maintain, and use the nation’s roadways; multiple mechanisms for communicating road weather information to varied users in ways that support better informed decision making; and an infostructure that takes advantage of new technologies to monitor and predict road weather conditions and then effectively convey road weather information to end users. The committee identified many opportunities for improving understanding, capabilities, and products in these five areas. In each of these research foci the proposed program should support activities that apply currently available knowledge and tools to the road weather problem, are new research and development efforts, and enable effective implementation of research results. The recommendations that follow highlight key activities in each of these categories. RECOMMENDATIONS TO OPTIMIZE USE OF AVAILABLE ROAD WEATHER INFORMATION AND TECHNOLOGIES 2. Make better use of currently available road weather information and technologies to increase capabilities for transportation research.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Archive and mine operational traffic observations to assess weather impacts. Some states and cities monitor traffic throughout their area and routinely collect data from traffic counters, video cameras, and other sensors. Often these data are used for real-time management of the transportation system but are not quality assured or archived in formats or in locations readily accessible to the research community. The committee recommends that the road weather research program take better advantage of these data because they provide many opportunities to learn about impacts of weather on traffic flow and refine estimates of traffic simulation parameters. This will require finding cost-effective ways to quality assure these data, archive them in easy-to-use formats, and make them accessible to researchers. Integrate available weather information into traffic planning and management models. The committee recommends research to improve the way weather effects are included in traffic and emergency management models, which currently are used for offline design and planning of transportation systems. Better accounting for weather in these models will allow researchers to assess the benefits of improved weather monitoring and forecasts on transportation operations and enable practitioners to more efficiently manage the nation’s roads. Use real-time weather information in the operation of the transportation system. The road weather research program should support development of operational modeling systems for roadway management that include realtime weather information. The use of real-time weather information to support the operation of the transportation system is in its infancy but should be encouraged; for example, the road maintenance community has made advances in incorporating real-time weather information in decision support systems for winter operations. Real-time road weather information would also be useful for warning drivers of dangerous weather conditions and for optimizing commercial vehicle operations.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services 3. Establish a nationwide real-time road weather observation system. Take advantage of existing observation networks and databases. The committee recommends that the road weather research program take full advantage of established environmental monitoring networks, including those from in situ and remote-sensing platforms and existing databases on soil type and land use characteristics. As a first step, efforts are needed to integrate and use information from Environmental Sensor Stations and meteorological mesonets with particular attention to seamlessness across state boundaries. A nationwide repository in which weather observations relevant to the roadways are collected and shared by all interested parties would be of great use to the road weather community. The committee recommends that the road weather research program support the design and establishment of a portal that allows access to (1) weather data relevant to the roadway; (2) state databases of relevant road characteristics, including pavement or concrete composition, road surface depth, and underlying soil type; (3) real-time road surface condition information; and (4) traffic information. Access to these data currently is constrained by the limited data availability and disparity of data formats used by states and municipalities. Having access to these data in standard formats would allow private sector companies to develop forecasting tools that could be easily and reliably applied in different states. Improve the existing observation system. To attain an improved road weather observation network the road weather research program should support efforts to establish standards for observing procedures and station siting to ensure that (1) the data are representative of the roadway environment and (2) new road weather stations and traffic monitors are added to optimally address both modeling and special observing needs. The National Weather Service, states, and other entities that perform weather observations should use these standards as they establish new sites to fill gaps in the current observational network. In addition to improving fixed road weather observation sites, expanded use should be made of mobile observing platforms. Such platforms could consist of a fleet of state- or city-owned vehicles, commercial trucks and buses, and even private vehicles. Vehicle observations of roadway temperature and surface traction could be of great use in providing a more complete and accurate picture of roadway conditions. The road weather community

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services should collaborate with the automobile industry in the design and deployment of these mobile observing platforms and ensure that these data remain open to access. Maximize utility and quality of road weather information. The committee recommends that the road weather research program take steps to maximize the utility and quality of road weather information. First, to facilitate sharing among multiple entities, the road weather community should help standardize formats of geolocated data and associated metadata (e.g., the National Transportation Communications for Intelligent Transportation System Protocol Object Definitions for Environmental Sensor Stations). Second, the community should standardize the presentation of road weather information (e.g., in terms of units, colors, or symbols) to user groups across North America. Third, to facilitate integration of information from different research communities, the community should use geographic information systems to analyze, manipulate, and display road weather observations, model output, and forecasts. Fourth, the community should establish standards and implement data quality assurance and control procedures. It is critical to ensure that all road weather observations are of sufficient quality to be used in the numerous desired data applications. RECOMMENDATIONS TO EXPAND ROAD WEATHER RESEARCH AND DEVELOPMENT 4. Improve weather and transportation modeling capabilities. Improve accuracy and resolution of road weather forecast products supporting both tactical and strategic decision making. The road weather research program should support development of tailored road weather information products to support real-time operations and both near-term tactical (0 to 6 hours) and longer-term strategic (> 6 hours) decisions by road users and managers. More accurate weather information products should be developed on fine spatial and temporal scales appropriate to the roadway environment, in part by taking advantage of advances in nested and ensemble modeling approaches. Producing road weather forecasts for the 2- to 6-hour timeframe presents the greatest research challenge because current data become less useful and some models may not have reached the point where they can provide useful output. As a

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services result, this short-term forecast problem likely will remain a focus of the human forecaster and newly emerging statistical tools for the near future. The newly developed National Digital Forecast Database from the National Weather Service provides forecasts across the United States on grid spacing no greater than 5 km and may provide a logical starting point for either user-developed applications or further enhancement by the private sector. Improve prediction and warning of weather-influenced hazards that rapidly impede roadway use. The road weather research program should support research to improve predictions and warnings of weather-induced hazards that rapidly impede roadway use, such as flash floods, avalanches, mudslides, and other debris flows. Better understanding of the causes of these hazards and how best to respond to them could help avoid loss of life and property. Existing observational and forecasting capabilities need to be assessed and significant gaps should be addressed. Improve empirical and numerical modeling techniques to account for both the roadway atmosphere interface and the surrounding environment. The roadway environment consists of two components: (1) the road surface and (2) the weather and visibility conditions directly above the road. For the former the committee recommends that research be pursued to improve one-dimensional modeling techniques for the roadway-atmosphere interface, the region that extends a few meters above and below the road surface. Advances in this area would enable better forecasts of road surface temperature, leading to better forecasts of frost and black ice. For the latter, empirical and multidimensional modeling approaches should be developed to account for local terrain, land cover, surface composition, and other geographic features that affect the exposure of the roadway to infrared and solar radiation (direct and indirect), wind, and precipitation. Such models need to provide improved forecasts of road surface temperature and condition (e.g., dry, wet, frozen surfaces) as well as fog, wind, and other localized atmospheric phenomena. Develop end-to-end models that assess and predict weather impacts on roadway conditions and operations. The road weather research program should support a long-term, interdisciplinary effort to develop end-to-end modeling systems. The required

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services modeling system would have to incorporate (1) current weather and pavement conditions; (2) “future” and forecast weather conditions; (3) a model of road conditions, especially road temperature and traction; and (4) a traffic simulation model that includes the reaction of drivers to such conditions as precipitation, high winds, low visibility, slick pavement, and congestion mitigation strategies (e.g., timing traffic lights, commuter highways, weather-controlled dynamic speed limit signs). Used in an offline planning mode, such a system has enormous potential to enable road managers and emergency responders to develop better proactive responses to extreme weather conditions. As understanding, modeling sophistication, and computer capabilities allow, such models ultimately could be run in real time to assist in the routine management of the transportation system, thereby enhancing safety, capacity, and traffic flow. 5. Develop observing capabilities to measure the performance of road weather forecasts. The committee recommends that the road weather research program develop special observing facilities to validate forecast tools and verify road weather forecasts. Ideally, these observing facilities would be located along the national corridors and at the regional centers identified previously. In some cases these facilities could consist of permanently instrumented arrays, but to be cost effective most should consist of supporting infrastructure that facilitates the rapid deployment of instrumentation for occasional intensive observation periods. An important aspect of the recommended work would be the collection of micrometeorological measurements necessary to develop, improve, and validate the models. 6. Develop methods for estimating and conveying the degree of confidence in road weather information. The road weather research program should support the development of means for estimating the inherent uncertainty in road weather information. Advanced weather decision support systems that assimilate many diverse sources of information need to estimate uncertainty and provide easily understood metrics to aid users in making optimal decisions. New methods are needed to enable more effective communication of uncertainty to a wide variety of users.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services 7. Improve road weather instrumentation. The road weather research program should support efforts to establish science-based standards for road weather sensors and to implement procedures to test, compare, and certify that sensors meet these standards. The comparison and testing procedures need to ensure that the results are applicable to a field setting. The committee recommends support for the development of improved sensor technology specific to road weather applications, such as for the amount of ice, all-season precipitation, present weather, and chemical composition of the slurry on the road surface. Research is needed on design and deployment of sensor systems to provide data more generally representative of the traveled road surface and that are reliable under a wide variety of weather and traffic conditions. 8. Support human factors research to obtain desired responses to road weather information. The road weather research program should support research into the human and cultural factors involved in driver decision making under a variety of weather conditions and in driver response to new technologies for the delivery of road weather information. Important aspects of this research include the information, content, and format for optimum response, and safe methods for communicating with vehicle operators, especially during hazardous weather conditions. The Federal Highway Administration’s program for an Advanced Traveler Information System has acknowledged that although technology exists to display information to the driving public, there is little knowledge to guide the proper selection of methods and displays. This research should build on the work done by the Advanced Traveler Information System, Commercial Vehicle Operations, and Advanced Traffic Management Systems, and be compliant with the National ITS Architecture Maintenance and Construction Operations user service bundle. Additional research is needed on effective communication of road weather information to traffic managers, maintenance personnel, and emergency managers because they have specialized needs that are significantly different from those of the general public.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services RECOMMENDATIONS TO EFFECTIVELY IMPLEMENT NEW SCIENTIFIC AND TECHNOLOGICAL ADVANCES 9. Develop new means to effectively communicate road weather information to a wide range of users. The road weather community should take advantage of new and up-coming advances in technology that will enhance communication to users. Along with expanded observational capabilities, advanced communications technology must be deployed to enable instruments to transmit data back to central processing centers and to relay processed weather information back to drivers and other users. Advances in wireless communication hold much promise for providing location-specific weather information to mobile users, but the challenge of determining how best to use these communication technologies remains. 10. Pursue nationwide operational capability as research results become available. Develop a robust national roadway infostructure. Major components of a roadway infostructure are being developed. The committee recommends that the road weather research program proactively participate in this effort to ensure that the road infostructure of the future incorporates a sophisticated network of road weather observations, including sensors embedded in the pavement, weather stations adjacent to the roadway, water level sensors near flood-prone routes, remote observations from satellite platforms, and instruments on vehicles themselves. Enable efficient technology transfer. The committee recommends that the national road weather research program involve operational users as part of the research and development effort from the beginning. The user community for road weather information is broad and includes the general public; commercial shipping and bus transit companies; emergency managers; those who build, maintain, and operate the nation’s roadways; and vehicle manufacturers. Early user involvement helps to ensure that the technology transfer path will be efficient and expeditious and will produce results relevant to the needs of the user community.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Improve education and training of road weather information users. The road weather research program should incorporate training on the use of road weather information and technology into driver education nationwide. This training needs to start with new-driver education and be reinforced periodically as new technology is introduced or other circumstances arise, such as when a driver moves to a new region with a different climate. In commercial settings continuing education on road weather information is recommended for drivers and dispatchers. Special efforts are needed in the education and training for such groups as road maintainers, emergency managers, and traffic managers. When new products or decision support tools are deployed, educational and outreach programs, pilot projects, operational demonstrations, and “table-top exercises” should be conducted on a regional basis. Seek out synergies and efficiencies between road weather research and parallel efforts regarding other modes of transportation. The committee recommends that the road weather research program routinely monitor research parallel to surface operations in aviation, rail, and transit to exploit applicable overlap. Many aspects of the proposed road weather research program could benefit research in aviation, rail, and other modes of transportation. Indeed, there are many synergies and efficiencies to be gained by coordinating research on meteorological phenomena that affect all modes and on the development of decision support resources. In particular the well-established aviation weather research program offers many lessons learned that should be examined by the emerging road weather research program.