4
Opportunities to Enhance the Road Weather System

Many of the building blocks for creating the road weather system of the future are available today. Chapter 3 of this report summarizes the capabilities and technologies that are already being applied to road weather problems or that could easily be used. However, fully achieving the vision for a highly effective road weather system will require the research and operational communities to address a number of gaps in existing knowledge and infrastructure. These gaps at least partly reflect the lack of integration between ongoing surface transportation and meteorological activities. Thus, the committee recommends that a focused and coordinated national road weather research program be established to provide leadership in defining priorities, supporting the necessary research, and implementing operational infrastructure. With an improved overarching direction for the road weather community, there are substantial opportunities to produce improved products of interest to the user community through increased coordination of efforts (e.g., Nixon, 2001). At the same time there is a need to address fundamental scientific unknowns and make required observations that have been lacking.

As a framework for this program the committee identifies the following five key research and development requirements:

  1. a robust, integrated observational network and data management system specifically designed to meet the need for enhanced road weather research and operational capabilities;

  2. 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;

  3. improved modeling capabilities and forecast tools designed to provide relevant, useful information to those who build, manage, maintain, and use the nation’s roadways;



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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services 4 Opportunities to Enhance the Road Weather System Many of the building blocks for creating the road weather system of the future are available today. Chapter 3 of this report summarizes the capabilities and technologies that are already being applied to road weather problems or that could easily be used. However, fully achieving the vision for a highly effective road weather system will require the research and operational communities to address a number of gaps in existing knowledge and infrastructure. These gaps at least partly reflect the lack of integration between ongoing surface transportation and meteorological activities. Thus, the committee recommends that a focused and coordinated national road weather research program be established to provide leadership in defining priorities, supporting the necessary research, and implementing operational infrastructure. With an improved overarching direction for the road weather community, there are substantial opportunities to produce improved products of interest to the user community through increased coordination of efforts (e.g., Nixon, 2001). At the same time there is a need to address fundamental scientific unknowns and make required observations that have been lacking. As a framework for this program the committee identifies the following five key research and development requirements: 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;

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services 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 effectively monitor and predict road conditions and then effectively convey road weather information to end users. Opportunities for improving understanding, capabilities, and products in these areas of a new road weather research program are discussed in the following sections. The committee believes that advances in each of these areas will be necessary to attain significant improvements in road weather services and the benefits that are expected, as a result, in safety and efficiency on the nation’s roads. Coordinating this body of work will require a management structure that engages the multifaceted “road weather community.” This community includes FHWA, NOAA, departments of transportation in each state, an important and vigorous private sector, the academic community, and professional societies (e.g., the American Meteorological Society) and other nongovernmental organizations (e.g., the American Association of State Highway Transportation Officials). One role of a national road weather research program would be to coordinate research, development, and implementation efforts undertaken by the various members of this road weather community. The recommendations in this chapter identify specific research needs that a new road weather research program should address, though in many cases the actual research, development, and implementation will fall to various members of the broader road weather community. Issues pertaining to management of a national road weather research program are addressed in Chapter 5. OBSERVATIONS A major objective of a new road weather research program should be to develop a robust, integrated observational and data management system specifically designed to meet the need for enhanced road weather research and operational capabilities. Many of the other objectives of the research program will depend on having implemented a road weather observation system, broadly defined; for example, improvements in understanding of road weather phenomena, modeling capabilities, and products and tools for end users require appropriate observations. This road weather observation system should bring together a wide variety of existing data streams and new data as necessary to obtain a

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services comprehensive picture of the roadway environment. Table 4-1 lists many of these observations. Several of the meteorological observations are currently used in an integrated fashion by weather forecasters and as input to numerical weather models. Other data, particularly those collected by the transportation community, are not yet integrated to the same extent or in a routine or standardized manner. Improved data management that enables efficient data sharing will be an important component of an improved road weather observation system. Take Advantage of Existing Observations and Databases As shown in Table 4-1, numerous observation networks are already available for assessing road weather; for example, many states have installed environmental sensor stations (ESS) along roadways to obtain targeted road weather observations. Data from ESS are essential to detecting and forecasting the effects of weather events on the roadway; however, they fall significantly short of the total amount of weather information needed to do this job well. The ESS data should be augmented with weather information from weather satellites, Next Generation Radar (NEXRAD) national radar network, surface sensors in other networks (e.g., Automated Surface Obsreving System (ASOS), aviation, agriculture, energy, water resources), vehicle probes, and weather data that can be derived from global positioning system satellites (e.g., see http://www.cosmic.ucar.edu). Bringing all these data sources together allows a much more comprehensive picture of the roadway environment to be derived and used to provide information to drivers, roadway managers, and researchers. New technologies are rapidly emerging to assimilate data from disparate sources, but very little has been implemented to directly benefit road weather. Some private sector companies have pioneered the process of aggregating weather data from ESS and other weather observing networks to prepare targeted road weather forecasts. In the case of winter road maintenance, data must become targeted specifically to the microclimate existing at or near the pavement surface. To accomplish this, sensor needs change significantly, and integration of other information, such as recent surface treatment history (e.g., plowing, sanding, and chemical application), become important factors. Treatment history collection and availability vary widely, but most of the larger state transportation agencies keep some type of records on time, equipment, and chemicals used in maintaining roads during snow and ice conditions. Methods for recording this information range from having operators manually record it to entering by means of computers when they input their duty time.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services At the Minnesota Department of Transportation, for example, individual operators input this information along with their duty times using a Webbased application. Information on individual routes—including time expended, equipment and materials used—allows managers to analyze past actions, plan for future events, and determine whether current strategies are producing the desired results. Research in the areas of Automated Vehicle Location systems and Web-enabled cell phones is allowing road treatment and condition information to be reported more frequently. In the future it may become common practice to have in-vehicle equipment installed on snowplows to continuously measure and report this information. Another untapped source of information are data on the characteristics of the surface and subsurface of the roadway that most state departments of transportation collect and retain during roadway planning and construction. This information is updated each time any construction or repairs are performed. Data on the road surface and subsurface composition are valuable inputs to pavement temperature models, in which the heat balance is affected by what is under the surface as well as what is above it. Research must be done to determine how changes in this profile affect the road surface and what would be the most efficient way to use this information to obtain more accurate pavement forecasts. Although many departments of transportation store this information in electronic format, they frequently identify it by mile posts, centerline distance, or stationing, which is significant only in its relationship to that particular road. In addition, different layers are identified by a numerical code that may be unique to that agency. If this information were to be used by an outside agency or vendor or shared among states, it would have to be converted to a geographic information system (GIS) format and layers identified with standard codes. A final set of observations that could greatly enhance the road weather system is average and real-time traffic information. Data such as the average number of vehicles and average vehicle velocities, as well as real-time values of these parameters, are useful for strategic planning and reactive purposes. The speed and volume of vehicles influences the heat and moisture balance of roadways as well as their operability. These factors change diurnally (e.g., rush-hour traffic, early-morning hours), intra-annually (e.g., during prime vacation travel times), and during special events (e.g., concerts, sporting events). All departments of transportation have some type of statewide traffic-data-recording system composed of a remote-sensing system (i.e., pavement loops) and a data recorder that is used for monitoring and assessing traffic volume and speed characteristics (Wolshon et al., 2001). Surveillance cameras also monitor speed and volume, with direct visual confirmation. As with other previously mentioned observation net-

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services TABLE 4-1 Existing and Potential Observations That Should Be Applied to Road Weather Research and Operations Observation Description Operated By Road Weather Application Limitations Automated Surface Observing System About 1,000 surface sites providing observations of sky and visibility, pressure, temperature, dewpoint temperature, wind, and precipitation amount • Federal Aviation Administration • Department of Defense • National Oceanic and Atmospheric Administration/National Weather Service Provides weather observations used as input to numerical weather prediction models to ascertain real-time weather conditions on a mesoscale basis and aid in weather forecasting • Observations are representative of small area directly adjacent to site • Mostly sited to meet aviation requirements • Lack of good winter precipitation observations Automated Weather Observing System Over 600 surface sites providing observations of wind data, temperature, dewpoint temperature, visibility, present weather, precipitation, cloud height, thunderstorms, and lightning • Federal Aviation Administration • State, local, and private organizations Provides weather observations used as input to numerical weather prediction models to ascertain real-time weather conditions on a mesoscale basis and aid in weather forecasting • Observations are representative of small area directly adjacent to site • Mostly sited to meet aviation requirements • Lack of good winter precipitation observations Various surface mesonets Similar observations as ASOS operated on a regional basis with higher density of sites • Oklahoma Mesonet • Atmospheric Radiation Measurement Cloud and Radiation Testbed • Many others Provides weather observations used as input to numerical weather prediction models to ascertain real-time weather conditions on a mesoscale basis and aid in weather forecasting • Observations are representative of small area directly adjacent to site • Sited to meet needs of specific mesonets • Data are not always easily accessible across mesonets • Lack of quality control and standards Environmental Sensor Stations A complement of atmospheric sensors adjacent to the roadway (air temperature and dew point, wind speed and direction, and optionally, pressure, precipitation occurrence, other precipitation Individual states or municipalities Provides most direct observations of roadway environment • Observations are representative of small area directly adjacent to site • Individual networks are not linked • Insufficient standards for instruments and siting

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Observation Description Operated By Road Weather Application Limitations   characteristics and visibility), pavement surface sensors (temperature, moisture, residual chemical composition, freeze point temperature), and sub-surface temperature probes     • Improvements in instrument technology needed Aircraft Communication Addressing and Reporting System Observations of temperature, humidity, and wind collected on commercial aircraft up to 15 km altitude Aeronautical Radio, Inc. Input to numerical weather prediction models and as aid in weather forecasting Not directly relevant to the roadway environment In situ observations from vehicles on the roadway Observations of air and surface temperature, humidity, surface friction, and visibility in the roadway environment Some prototypes being developed and tested, but not yet operational • Information provided directly to drivers • Input to road weather forecasts • Input to numerical weather prediction models • Challenges in communicating observations • Possibility for more observations than can be usefully applied Weather radars, including NEXRAD Nearly continuous monitoring of precipitation, including severe weather, and an ability to determine winds and detect blowing dust • National Weather Service • Federal Aviation Administration • Private sector, including television stations • Military Input into numerical weather prediction models (e.g., the Weather Research and Forecasting model) • For NEXRAD, scans below 0.5° above horizon not permitted so areas distant from radar not well monitored • Network not very dense • Cannot discriminate precipitation phase (liquid or frozen) • Excessive ground clutter contamination from anomalous beam propagation • Conflicting user requirements

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Observation Description Operated By Road Weather Application Limitations Wind and temperature profilers Remotely sensed observations of temperature, moisture, and wind up to 16 km above the surface • National Oceanic and Atmospheric Administration • Other state and federal agencies • Academia • Private sector • Input into numerical weather prediction models • When combined with SODARS, the 900-MHz band profilers can be used for microscale modeling of the roadway • Improve weather forecasts • Representative of a small area • Network not very dense Geostationary Operational Environmental Satellite, Polar Orbiting Environmental Satellite, and other satellites Observations at multiple wavelengths (e.g., visible, infrared, microwave) used to derive, for example, integrated water vapor and cloud-track winds, tropical cyclogenesis • National Oceanic and Atmospheric Administration • National Aeronautics and Space Administration • Military Improve weather forecasts Cannot resolve features on the roadway Traffic observations Traffic detectors and cameras Individual states or municipalities • Managing the traffic system during inclement weather • Input to energy balance models • Study of weather impacts on traffic • No standard format or reporting procedure • Expensive to store Recent treatment history Data record indicating the chemical application, plowing, or sanding of a given stretch of roadway Individual states or municipalities Input for forecasting road surface conditions and providing decision support for further treatments No standard format or reporting procedure Roadway surface and subsurface Surface and subsurface sensors used to measure temperature Individual states or municipalities Input for energy balance models that forecast road surface temperature Network not very dense

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Observation Description Operated By Road Weather Application Limitations Streamflow Measurement of the movement of surface runoff traveling in a stream • U.S. Geological Survey • National Oceanic and Atmospheric Administration • Others Useful for forecasting floods Network not very dense Landsat Land surface cover/land type National Aeronautics and Space Administration Input for energy balance models that forecast road surface temperature Maps and data require some user interpretation Global Positioning System Satellite-based system to show position on Earth’s surface; can also be used to derive total water vapor column Department of Defense operates the satellites; receivers are widely available • Useful for providing targeted geolocated information • Derived water vapor useful for improving weather forecasts Selective availability leads to degraded accuracy in position readings works, if traffic data are to be used by other agencies or vendors, standards for displaying the information must be established. Recommendation: 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.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services 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. Expand the Network Exploiting weather information to increase the efficiency of the roadway system requires weather, road condition, traffic, and other observations that are representative of the roadway. Additional observations are required at locations especially susceptible to adverse weather conditions, such as valleys where fog often forms, frost hollows, or roadways subject to high winds. Over the last 20 years most states have implemented ESS networks to collect valuable weather data in targeted locations. At the same time, various meteorological observing networks have been established to meet general weather forecasting needs, as well as those of more specialized sectors, such as aviation, forestry, or agriculture. These observational efforts must be expanded and customized to fully meet surface transportation needs by collecting tailored information along the roadways, particularly at vulnerable locations susceptible to adverse weather conditions; for example, the National Weather Service (NWS) should consider road weather needs in planning new observation sites. Although Road Weather Information Systems (RWIS) technology has been used for many years, research is needed to make optimal use of it; for example, only a few states have attempted to determine optimum sensor density. RWIS companies have recommendations for spacing of the sensors, but in most cases they are based on regional or national average estimates rather than site-specific analyses. Given funding limitations, roadway managers need refined methods to prioritize sensor locations in the network. A science-based method allows the determination of which sensors give the operator the largest value for the investment costs. Roadway managers also need methods of determining where to locate sensors, such as the optimal height above the road surface, distance from the roadside, or placement in

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services the road surface; for example, in some cases it might be more advantageous to locate a sensor far from the roadway to detect weather conditions that influence that segment of the system. Tapping into the data from vehicle probes would vastly increase the number of observations available for the roadway, much the way observations from aircraft have been exploited. Although the technology is already available, it is not used routinely. Commercial fleets represent an excellent opportunity for experimentation and evaluation of these data because they provide a representative sample from a manageable amount of data with tighter institutional control. Observational technology ranging from soil and pavement sensors to universal vehicular highway reporting is possible, providing exciting opportunities for expanding knowledge of the roadway environment; however, determination of what is to be measured, and where and when, are challenges. Research is needed to explore the quantity and accuracy of data needed for mesoscale forecast models, decision systems, and highway maintenance personnel. Who will do the research and where it will be conducted also must be explored. Recommendation: 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 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.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services Instrument Technology A final way to ensure robust observational capabilities is to make certain that the instrumentation provides high-quality, accurate data. Careful testing and calibration of sensors is an important step in improving instrumentation. Although testing and calibration standards have existed for atmospheric sensors for some time, current sensors, sensor standards, and instrument placement are tailored to meteorological needs and, in many cases, do not meet the specialized needs of maintenance, traffic, and emergency managers. For instance, precipitation sensors must be capable of accurately identifying precipitation type and amount as well as the liquid equivalent through all temperature ranges. There currently are no standards for surface and subsurface environmental sensors. More concerted research is needed to test and compare the pavement sensors. To deliver the accuracy and response time required by sensor users, close attention must be paid to sensor design, installation, and calibration. This is needed to ensure that the thermal properties of the surrounding pavement are accurately represented by the sensor. The majority of research and development of environmental sensors takes place in the private sector, which has led to new and improved sensors being offered by multiple companies; however, most of these sensors have not been rigorously tested and compared, meaning that it can take many years to design and get funding for an experiment that tests the sensors in a real-world setting, and then run the experiment long enough to get sufficiently representative weather conditions. By the time a research group has undertaken all of these steps it is likely that the sensors being tested will be outdated. An additional problem for testing pavement sensors is the difficulty of creating a controlled experiment as roadway maintenance engineers prefer to treat the roadway when called for. As a result, insufficient information is available to consumers when choosing which sensor to purchase. To date, environmental sensor users have relied almost exclusively on accuracy, installation, and calibration information provided by product manufacturers. While this information can be useful (e.g., Partanen et al., 2003), it is often produced in controlled laboratory or test-bed conditions, and therefore can be far removed from real-life conditions that affect sensor performance. There are currently two projects under way to test environmental sensors in an operational setting: (1) Aurora project 2001–2004, Temperature Sensor Accuracy, and (2) an Aurora-initiated project that has now developed into National Cooperative Highway Research Pro-

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services near-future traffic conditions are being developed. Two such models are the Dynamic Network Assignment-Simulation Model for Advanced Road Telematics model (DYNASMART-X) and the Dynamic Network Assignment for the Management of Information to Travelers model (DynaMIT). These models try to predict the behavior of vehicles by simulating thousands of driver choices every few seconds and predicting when those choices will converge to create congestion (Vatalaro, 2001). These models show great promise for supporting traffic management in developing real-time routing and rerouting scenarios for more efficient system management, but they do not ingest weather data. Coupling atmospheric and traffic simulation models provides opportunities to address significant problems related to roadway safety, capacity, and efficiency. Some of the areas of opportunity are as folllows. Congestion Mitigation: Coupled models for urban roads to detect and predict weather elements that contribute to congestion assimilate the dynamic data into the traffic simulation model and modify the traffic flow accordingly. The resultant output could trigger mitigation strategies, such as access control, ramp metering, speed management, weather-related incident detection, weather-related traffic signaling, and public advisories. Emergency Evacuation Strategy Development: Coupled models covering regional areas that contain urban areas, nuclear power plants or other facilities that have potentially hazardous releases, and hurricane-prone stretches of the U.S. coast could predict the movement and concentration of hazardous materials by local winds that feed into traffic simulation models that identify safe and unsafe evacuation corridors. These identified areas could trigger mitigation strategies, such as contraflow, access control, incident response and public advisories to facilitate the movement of people away from the danger in the most efficient manner. Use of the system for hurricane evacuation would identify similar hazardous areas to be avoided and initiate similar mitigation strategies, particularly contraflow and access control. Although both model development paths are fairly mature, there is still much research that is required to tap the opportunities outlined above. Work needs to be done to determine how to best use weather information in traffic simulation models to allow them to further optimize traffic flow for a range of weather conditions in a robust and stable manner. A phased approach to development is likely the best path, beginning with more straightforward problems, including simple prototypes, and then

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services migrating to more complex problems; for example, determining the effect of light, moderate, and heavy precipitation on traffic flow along certain corridors could be a beginning point. More complex problems, such as drifting snow on the roadway and crosswind effects on high-profile vehicles, would be addressed at a later stage. Given the current strong focus on homeland security, it might be appropriate to begin the research with coupled systems that take a simple, first-guess estimate of a toxic plume’s location and movement and determine how this information can be effectively used in a traffic simulation model. Predictions of plumes that are highly complex in their movement to local winds and atmospheric stabilities could be addressed later as confidence in the coupled system increases. Recommendation: 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 real-time 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. End-to-End Models Decision support systems are the largest category of weather-related needs for the transportation system manager. For decades weather information has been assimilated by these managers using a method that some refer to as “swivel chair integration.” That is, the decision maker considers each separate category of weather-related information independently and then tries to integrate the accumulated information manually to make a critical decision. Many managers have learned to do this quite well, but their decision making process will almost always be different than their colleagues; this means that inherent inconsistencies exist across the team of decision makers in any given facility. If one adds to this a process that is very inefficient by its nature, there is no wonder that most facilities have come up with a consensus process that

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services is conservative for the group. In other words each decision associated with a weather scenario is not optimized in a benefit-cost sense. Winter maintenance rules of practice, for example, tend to be too conservative, usually resulting in a higher than required margin of safety and the application of more chemicals to the roadway. This practice results in higher costs and negative effects on the environment. The roadway management decision process is further complicated by the fact that weather is only one of several decision criteria that need to be assessed. A reliable, consistent decision maker must integrate all these factors to be successful. Modern decision support systems can integrate all this information consistently and reliably, but use of such systems is rare in today’s roadway management systems. The need for decision support applications is widespread, even in the traffic management community. Some of the needs are as follows. Integration of weather-based decision support systems with traffic simulation numerical models is required to diagnose and predict traffic flow in urban areas for short periods into the future. The primary weather-related information needed is pavement condition (e.g., wet, dry, icy, snow-covered), precipitation type and rate, wind speed and direction, road friction measurements, and obstructions to the driver’s vision (e.g., sun glare, fog, smoke, dust, or blowing snow). This decision support information is needed to advise motorists of predicted and prevailing conditions, to alter the state of roadway devices to control traffic flow and regulate roadway capacity, and to supply resources to roads to mitigate weather impacts. Decision support technology is needed to trigger warnings of dangerous conditions along the roadway resulting from weather events. Some examples are reduced driver visibility ahead, cross-winds exceeding 50 mph ahead that can tip over high-profile vehicles, severe thunderstorms (hail, heavy rain, high winds), tornadoes, icy road conditions ahead, flooding on the roadway, hurricane conditions, movement of wildfires near the roadway, and the movement of chemical, biological, or nuclear hazardous material along the roadway (OFCM, 2002a). Decision support technology is needed to optimize commercial vehicle operations. This would enable truck routing to exploit weather information for just-in-time delivery and to minimize fuel consumption and allow the safest routing for hazardous cargo shipments based on road condition and winds relative to vulnerable assets and temperature.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services An end-to-end road-modeling system has enormous potential to enable road managers and emergency responders to develop better responses to everything from developing strategies for safer driving in fog and responding to extreme conditions, such as evacuating the coastline in anticipation of hurricane landfall. The required modeling system would have to incorporate changing weather conditions, preferably with high horizontal and temporal resolution to account for local variability; a model of road conditions, especially road temperature and slipperiness; a traffic simulation model that includes the reaction of drivers to such conditions as precipitation, wind, and traffic; and traffic mitigation procedures, such as timing traffic lights, switching direction of highway lanes, and dynamic message signs. Recommendation: 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 road-modeling systems. The required modeling system would have to incorporate (1) current weather and pavement conditions; (2) “future” or 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. COMMUNICATION SUPPORT FOR ROAD WEATHER INFORMATION USERS The road weather research program should support the development of multiple mechanisms for communicating road weather information to a range of users in a manner that supports more informed decision making. Communication is important for making the research results useful to drivers and those who build, maintain, and operate the roadways. Development

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services of improved mechanisms for communicating weather information to roadway users is already under way: traffic and weather information is often relayed together in radio and television broadcasts; many states have implemented 511, a single nationwide phone number for traffic and road condition information; and roadway managers are making greater use of dynamic message signs. The Maintenance Decision Support System pilot project has developed a prototype tool with which winter maintenance operators can obtain highly targeted road weather observations and forecasts, as well as assistance in choosing the best treatment options. The committee sees a road weather research program in which two-way communication allows researchers to learn from stakeholders about their needs and thus build better decision support tools for them. In addition to setting up effective mechanisms for communication, the road weather research program should support research on ways to improve communication. Two areas on which this research should focus are improving the ability to convey levels of confidence associated with road weather information and taking advantage of newly available communication tools. Conveying the Confidence Level Testimony to the committee by both users and providers of advanced weather technology indicated a strong need for conveying not only timely, accurate, and reliable diagnostic and prognostic information to decision makers, but also the degree of uncertainty in this information. Users have historically shied away from probability metrics associated with forecasts, in some cases because the need is misunderstood and the metrics are considered merely a way for prognosticators to dodge their real need: a perfect weather forecast out to a week or so. Even though the user might have understood the need for the uncertainty metric, intelligent use of the information was another problem; very few users had systems that could ingest this information and analyze its value to the decision maker. Now, advanced weather decision support systems that assimilate many diverse sources of weather and operational databases have uncertainty metrics as a by-product, and in many ways depend on the metrics for their value to the user, for example, cost analyses can be done effectively by ingesting probabilistic weather data along with information about available resources and operational status. In addition to developing robust methods for estimating the degree of confidence in road weather information, it is important to devise effective

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services methods of conveying uncertainty information to users. Communicating uncertainty was the subject of a recent National Research Council workshop during which lessons learned from several weather and climate case studies were discussed (NRC, 2003a). The workshop participants found that communicating uncertainty is a critical part of decision making for users of weather information, and it is important to communicate both why information is uncertain and why that uncertainty matters. The workshop report stresses that multiple measures of uncertainty, both quantitative and qualitative, should be communicated, along with a context to tie the information to past experiences and to make the uncertainty information more tangible. Despite advances, much research is needed on conveying uncertainty in road weather information products and improving easily understood metrics to facilitate user decision making. New ways are needed to include a more complete representation of the sources of uncertainty and to communicate the context of the information. The format of information (e.g., text, graphics, numbers) may serve to modify its interpretation even when the underlying information is unchanged. Simply repeating the same information tends to convey that it is more credible. Recent memory of similar events may color interpretations, whereas prior education about how to interpret information can improve decision making. Even though the NWS has developed products to provide uncertainty information to address some user needs (e.g., the probability of measurable precipitation or the seasonal and monthly outlooks), much work needs to be done with users to address the full expanse of their needs and determine the best ways to convey uncertainty to them. This is particularly true with the newly implemented National Digital Forecast Database, which presents very high resolution (5 km grid spacing) forecasts through seven days without the benefit of confidence or uncertainty information. Recommendation: 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 New Communication Tools Systematic collection and dissemination of road weather data are critical to the success of the road weather research program and require robust communication technology. For example, collection of real-time data invariably involves some form of data logger at the measurement site, telecommunication means (e.g., telephone line, fiber line, microwave relay), and a reception facility that moves the inflowing data stream to archival servers. These communication means are often already in place in roadway right-of-ways, either for commercial communications providers, law enforcement, or state departments of highways themselves. A number of new wireless technologies may enable communication with motorists when and where they need it. The technologies that hold the most promise are satellite radio, cellular, and wireless local area networks. When considering how each of these technologies may be used for communicating road weather information with drivers, it is necessary to consider how much information can be transmitted and whether it is possible for two-way communication, how far the signal can be transmitted, and how ubiquitous the technology is. Also weighing into the decision are human factors, such as familiarity, ease of use, and cost. Each of these technologies is capable of transmitting different bandwidths, which affects the type of information that can be sent. Satellite-based Digital Audio Radio Service, which provides radio coverage across the continental United States, has been implemented recently. With a satellite-capable radio receiver and a subscription to a satellite radio service, consumers at home or in their automobiles are able to receive detailed graphic weather and traffic reports that are customized for their location. Although this technology currently is available only to emergency response vehicles, it may become commercially available soon. Several automobile manufacturers are beginning to offer satellite radio as an available factory option. Satellite radio is an improvement over regular radio because it has better coverage and bandwidth, while allowing geolocated transmissions. Nevertheless, regular radio remains critical for transmitting weather information to drivers because the costs to consumers are minimal. Cellular communication provides many features that match the needs for communicating weather information to drivers. In most parts of the country, cellular signals have a range of miles (see Figure 4-6) and a relatively ubiquitous infrastructure in place, with many of the cellular towers installed along interstate highways. The technology is flexible and the focus

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services FIGURE 4-6 Schematic illustrating the spatial range over which different communication technologies extend. SOURCE: Ian Ferrell, Microsoft Corporation. of much innovation, making it likely that applications for the road weather problem might be developed. In particular, it is possible to send individualized broadcasts, for example with information about weather on an adjacent stretch of road, from each cell tower. Again, human factors, such as familiarity, ease of use, and cost will play a role in the feasibility and success of such applications. Wireless local area networks have a much larger bandwidth than cellular and recently were tested successfully at highway speeds of over 200 mph (http://wireless.itworld.com/4260/031020necwifi/page_1.html). Implementation of this technology may occur soon, but until then wireless local area networks are well suited for in-car communications with other devices and for communication between the vehicle and physical points, such as a home, gas station, or rest stop. Very detailed information about local weather and road conditions, including animated forecasts or other large-bandwidth data, could be transmitted to a vehicle located at a rest stop. As with

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services cellular, wireless local area networks support two-way communication and are the focus of much technological innovation; however, little infrastructure has been developed to support wireless local area networks communication with vehicles, so coverage is very poor at this time. Recommendation: 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 upcoming 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. INTEGRATING WITH THE EMERGING INFOSTRUCTURE A final but nonetheless critical emphasis of the road weather research program should be to develop a telecommunication infrastructure that takes advantage of new technologies to effectively convey road weather information to end users. Previous recommendations in this report have included the establishment of a nationwide real-time road weather observation system. Such a national integrated network of fixed and mobile stations would generate an enormous amount of valuable information about the weather affecting roads and travelers and the resultant condition of the road network. All of these data would need to be carefully and uniformly quality controlled to common national standards to ensure consistent and appropriate use by multiple agencies (also a prior recommendation). The meteorological community, both public and private, would make use of this rich dataset to refine numerical weather predictions of the atmosphere and determine future impacts on the roadway environment (Smith, 2001). Weather impacts permeate the entire transportation system and must be factored into all manner of road transportation operations and systems. Clearly, there is a substantial telecommunications requirement to first collect road weather and condition data from multiple fixed and mobile platforms and then move road information and finished products to transportation managers and road users.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services A national telecommunications and information technology infrastructure or “infostructure” is required to move all this information. This infostructure must be adapted to respond to the specific needs of the road transportation sector. The National ITS Architecture, discussed in Chapter 3, provides the overall blueprint for this infostructure. It starts out by identifying the basic elements of road transportation and then groups them into four categories or systems: travelers, vehicles, field, and centers. Within each of these systems, specific elements or subsystems with unique needs are defined; for example, the vehicles group includes maintenance and construction, transit, commercial, emergency, and regular passenger vehicles. Sub-systems are defined, based on extensive user interviews, for the other main systems: centers, field, and travelers. The National ITS Architecture then goes on to define basic telecommunications links between all of these systems. These are grouped into four classes: (1) from the centers to the field, regular wireline (fixed-point to fixed-point) communications suffice and are specified; (2) between the field and vehicles, Dedicated Short Range Communications provides the solution from fixed points to moving vehicles; (3) vehicle-to-vehicle communications; and (4) wide-area wireless communications. The very serious safety and efficiency impacts that weather exerts on road transportation are recognized and have been included throughout the Architecture. Each of the fundamental activities leading to better management is covered: data acquisition, processing, dissemination, and integration into end-to-end applications. In responding to the needs of road transportation the meteorological community must take full advantage of the infostructure as specified by the Architecture. Road weather and condition data are collected from multiple fixed sites and from vehicle fleets hosting road and weather sensors. Links are specified to move the data to primary operators of the sensing equipment, the road maintenance and construction community. The architecture then provides for the data to be moved to other agencies for processing into useful information. This includes quality assuring the data, analyzing them, generating road weather forecasts from them, and finally packaging and returning all this information to all manner of road transportation users. The applications range from integrating time and location information into future in-vehicle audio and video display systems to ensure rapid and easy assimilation by motorists while driving to integrating high-resolution road weather modeling outputs directly into end-to-end solutions for road maintenance and traffic and emergency management.

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Where the Weather Meets the Road: A Research Agenda for Improving Road Weather Services The transportation community has taken the first and most important step of recognizing the impacts of weather and the need to factor weather information into their operations. The National ITS Architecture incorporates design elements for road weather telecommunications. The weather community needs to work through the Architecture with transportation professionals to respond to road transportation’s specific needs. This process is already engaged. Weather and transportation professionals worked together on ITS America’s Weather Information Applications Task Force and the FHWA’s own Maintenance and Construction Operations (MCO) User Forums to develop the MCO User Service. Other activities are currently being pursued in the standards area, another main application area for the Architecture. Such standards as the National Transportation Communication for ITS Protocol Object Definitions for Environmental Sensor Stations have benefited from the participation of weather and transportation professionals. That standards effort is nearing maturity, but others are at an early stage and will need the participation of both communities in order to succeed. Numerous other future applications will require both weather and transportation expertise. The transportation community is developing, with the National ITS Architecture as the fundamental design, a robust national infostructure adapted to the specific needs of road transportation. That infostructure presents an enormous opportunity for weather professionals to work with the transportation community to prepare and effectively deliver uniquely adapted road weather products. It is therefore crucial for the meteorological community to develop road weather professionals and engage the transportation community in the development of weather solutions for road transportation. Recommendation: Develop a robust national roadway infostructure. Major components of a roadway infostructure (a network of data collection and dissemination necessary to support real-time management and operation of the roadway transportation system) 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.