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Publication Number:      Date:  March/April 2002
Issue No: Vol. 65 No. 2
Date: March/April 2002


Weather: A Research Agenda for Surface Transportation Operations

by Gary G. Nelson and Rudy Persaud

Environmental Impact

Highway construction is a very structured, well-planned process; however, both during construction and afterward, highways exist in a natural environment that is neither planned nor tamed. Weather is nature's "environmental impact" on highways, and it can often be irritating and sometimes be disastrous.

The effects of weather played a big part in the creation of a federal government office in 1893 "to make inquiry regarding public roads" and to disseminate the information. The Federal Highway Administration (FHWA) traces its history to the Office of Road Inquiry in Department of Agriculture. This impetus to create this office came from the lobbying of the Good Roads Movement, protesting public roads that were, according to one contemporary slogan, "wholly unclassable, almost impassable, scarcely jackassable!"1 The mantra of the Good Roads proponents was to "get the farmers out of the mud" by constructing good roads that made it easier and faster for the farmers to get their products to market.

Photo of speed limit sign covered by flood waters

This speed limit sign covered by flood waters shows a strong relationship between surface transportation and hydrology. Inland flooding is a major threat to safety and facilities. It requires effective, local-scale prediction, and coordinated response from maintenance, traffic, and emergency management crews.

In the 21st century, we still need to anticipate weather and to deal with its adverse weather effects, using information technology and operational techniques. While the focus has changed from getting out of the mud to getting out of the muddle of congestion and to improving highway safety, many promising programs that would do this are, in many ways, in the same neophytic stage as the "Good Roads" movement was a century ago.

Weather and Highways

The significance of weather to highways should not be overstated, but neither should it be lost. The significance of weather is that it crosscuts almost every goal, use, and operation of highways, and that is exactly why it is at risk of becoming lost. It has no single organizational focal point within the highway community. Meteorology, from a transportation perspective, is focused mostly on the atmosphere and, by extension, to those who fly in it. There is little focus on the earthly ribbons of pavement where the majority of commerce flows.

Nevertheless, weather is an important dynamic factor that affects maintenance, traffic flow, and disaster response, among other things. To make weather issues an important part of highway programs, people who manage highway operations must seek new techniques and intelligent transportation systems that complement the amazing system of weather-information collection, analysis, and forecasting that exists in the United States.

Although weather affects highway planning and design, only highway operations can deal with the weather threats that change from hour to hour and, sometimes, from minute to minute. Table 1 summarizes the subclimatic concerns about weather under each of the highway goals.

Weather and Operations

The weather threats and the losses cited in the table cannot be eliminated. However, as in the case of safety, a systematic and multipronged approach will have important benefits and will lessen the effect. A focus on weather and operations could reasonably have a 5-percent to 10-percent positive effect on any of the goals, and that is easily equivalent to saving billions of dollars per year across the United States.

The systematic and multipronged approach has to include operational and informational integration.

Operational integration concerns the collaboration of maintenance, traffic, and emergency management functions, and their relationship to highway users. Operational management is split among jurisdictions and agencies, and this presents the challenge of horizontal coordination.

Table 1 — Why Weather Matters to Highway Goals
Goal Weather Effects Magnitude
Mobility Loss of capacity through loss of friction, impaired vehicle operation, reduced visibility, blockages, and equipment outages. Weather, along with incidents and work zones, is a major cause of non-recurrent highway delay. Average to moderate weather events result in about a 12-percent travel-time delay.
Safety Cause of crashes through similar effects as on mobility. About 6,600 fatal crashes each year in adverse weather, and 470,000 injury crashes.
Productivity Cause of increased cost of all productive activities, including highway operations. A total of $2 billion per year is spent on winter road maintenance, and damage costs are about $5 billion. Shutdowns due to snow cost between $20 million and $70 million in an urban region. Loss due to delay in freight shipments and damage to goods is not well-known.
Environmental Quality Degradation of transportation air quality, the cause of anti-icing chemical use, and the dispersion of all contaminants released on roadways. Ozone attainment depends on only the four highest concentrations each year, and these critically depend on weather conditions. There are 15 million tons/yr of road salt applied against ice. Silting and hazardous materials (hazmat) effects depend on the weather.
National Security Mobility of military movements and the vector of any chemical, biological, or nuclear releases. Hard to assess; however, timely and accurate information is critical.
Organizational Excellence All above weather effects potentially decrease customer satisfaction. Partners, customers, and employees will find it difficult getting to destinations and performing work.

Intermodal coordination among all the surface transportation modes is also required.

However, operational management in surface transportation, unlike in air traffic management, has little positive control over transportation users, and user behavior on the transportation system is based mostly on information that comes from sources other than operational management authorities. This creates the challenge of vertical coordination between the operational staff and the public.

Weather is just one element of the information needed to influence the decision-making of operational managers and travelers. Informational integration is about the selection, fusion, and presentation of all relevant information. However, some fundamental principles apply when dealing with the weather:

A research agenda to determine how to more effectively use tools and techniques to deal with weather threats to surface transportation operations should emphasize the need to make early decisions. If actions are to be complementary and if scarce resources are to be shared in times of large-scale disasters, appropriate decisions must be coordinated so that actions can be integrated.

Much must be done to coordinate decisions within the transportation community, as well as between the transportation and weather worlds. The task of integration is not unique to weather; however, because weather has a range of scales of predictability, extent, and severity. Linking the transportation and weather domains also provides interesting opportunities for interdisciplinary, interagency, and public-private linkages. An aggressive research agenda could produce fertile synergies.

Photo of road with "Fog Ahead" sign

Environmental threats to drivers, such as fog, come from combinations of weather, surface, and sub-surface conditions. They are dynamic and require more than static signs to achieve effective driver and highway-operator responses.

Where Is the Surface Transportation Weather Research Agenda?

In September 2000, the deputy secretary of the U.S. Department of Transportation (DOT), Mortimer Downey, spoke to the National Research Council about the development of a National Transportation Science and Technology Strategy, including the need and value of additional weather-related research and development (R&D).

"Advancing technologies are the primary means by which transportation improvements can be made to meet 21st century transportation requirements," Downey said. "The development and implementation of these advances require the coordination of technological progress from diverse areas and working with stakeholders in each of these areas, including federal agency programs and industrial participants, as well as state and local governments. ... By nurturing several of these partnership initiatives, we create an opportunity to bring together crosscutting research within the federal government and the private sector to support these transportation goals. Some of the partnerships, such as those proposed for Enhanced Transportation Weather Services and Transportation Infrastructure Assurance, are in areas where DOT does not have focused or well-established R&D programs. These areas, however, serve a critical function for achieving transportation goals."

In contrast to surface transportation, the importance of weather research is well-recognized by authorities in aviation. The Federal Aviation Administration (FAA), the National Weather Service (NWS), and the U.S. Department of Defense (DOD) are the "Big Three" in weather. There are tight operational links between FAA and NWS, and FAA spends more than $400 million per year on weather operations and systems acquisition. The Aviation Weather Research Program under FAA spent $30 million in 2001.

FHWA is spending about $2 million per year on road/weather research through the Road Weather Management Program (RWMP), managed by the Operations Core Business Unit. RWMP also includes participation from the Research, Development, and Technology Service Business Unit. The funding is mostly through the intelligent transportation systems (ITS) research program since there is currently no separate authorization for road weather research.

Prior to the initiation of RWMP, there were notable accomplishments, such as the Strategic Highway Research Program (SHRP) that promoted the use of Road Weather Information Systems (RWIS) to provide information for early decisions about anti-icing techniques for winter road maintenance. However, to a significant extent, the SHRP tools and techniques were imported from abroad.

Since the origination of RWMP in the rural ITS program, significant projects have included:

These projects focus on development of the information thread, from observation to decision support, primarily for winter road maintenance and on the subclimatic scales (i.e., for operational management and traveler information, but not resource planning). Advanced Transportation Weather Information System (ATWIS) and Foretell are considered first-generation decision support. ATWIS originated in 1995, outside of RWMP, and Foretell was the first RWMP operational test awarded in 1997. The projects have improved RWIS by forecasting road/ weather conditions through numerical weather modeling and improved dissemination of information to DOT managers and travelers. Both projects are in multistate, commercial operation. The STWDSR project, which began in 1999, is aimed at next-generation requirements that are being demonstrated through the MDSS, now in its second prototype-development year. The five small COMET grants awarded in 2000 are for two-year, university-based research into applications of environmental sensor stations (ESS). The ice detection project, completed in 2001, developed infrared sensors that extend the range and detection confidence of in-pavement ESS.

The projects listed represent the variety of participants and institutional arrangements that RWMP is fostering. ATWIS began with university research at the University of North Dakota and has spun off a private deployment venture. Foretell started as a three-state consortium with a private deployment partner. The STWDSR and MDSS projects have developed a large stakeholder group of DOTs, private vendors, and researchers. The MDSS project is being conducted by a university research consortium and by five federal laboratories under the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Department of Defense.

The MDSS products will be licensed for private deployment. The COMET projects are by NWS, state DOTs, and university partnerships. The program has proven that a little money can leverage significant results and that more institutions can be enlisted in additional projects for a wider range of applications.

In addition to these projects, an important link between highway research and the weather community has, surprisingly, been created through the technology of the differential global positioning system (DGPS). Errors detected by DGPS are determined by the atmosphere and, in particular, by the integrated precipitable water vapor in the signal paths from the satellite to ground reference stations. The water vapor data are an important augmentation to weather observations and can be used as a detector of precipitation events. Because the DGPS program is partly under surface transportation auspices, FHWA is working with the Forecast Systems Laboratory of NOAA, one of the MDSS partners, on the demonstration of the weather-prediction improvements possible with the DGPS observations.

The multimodal implications and the crosscutting between operations and research mean that there has to be coordination among DOT's surface modal administrations and its Research and Special Programs Administration (RSPA). RSPA is currently sponsoring transportation remote-sensing and radar-based weather-prediction projects. And despite the primarily above-ground interests of FAA, there are many areas of surface interest in the Aviation Weather Research Program (for instance, icing and general improvements in prediction).

In interdepartmental coordination, the Office of the Federal Coordinator for Meteorology (OFCM) has played an active role during the last five years. OFCM was created mainly to be a broker for the large acquisition programs for satellites, radar, and surface observation systems among the "Big Three." OFCM was in a good position to recognize the opportunities for surface transportation and has sponsored two national symposia on surface transportation weather (1999 and 2000), as well as including the surface administrations in OFCM committees.

Where Is Surface Transportation Weather Research Going?

Photo of an environmental sensor station

More environmental sensor stations, like this one, are needed to monitor specific road conditions and to support the full range of warning and prediction needs; however, this is expensive. Research must answer the questions of how many, where, what technology, and the tradeoffs with other weather sensors.

Over the past decade, the Aviation Weather Research Program has built up to its present level and its ability to map out a long-term program with experienced university and national laboratory partners. Since the RWMP and OFCM efforts started only a couple of years ago, the progress to date for surface transportation is notable.

RWMP is starting to extend its concern to emergency management (primarily with respect to hurricane disaster management) and traffic management. The development of decision-support systems has created strategic alliances with some of the national laboratories that support the research of the "Big Three." RWMP has been active in the OFCM efforts and has begun the inter-federal linkages to the large variety of agencies concerned with surface transportation and weather information —from the U.S. Department of Agriculture (transportation of produce) to the U.S. Department of Energy (movement of hazardous materials) and to the National Aeronautics and Space Administration (ground movements of space shuttles).

Organizationally, there are significant challenges to integration of surface transportation weather. A common research agenda and the pooling of resources require extensive inter-federal coordination. The Federal-Aid Highway Program is essentially a federal-state program. This creates a much more diffuse constituency than for many of the other agencies. The states, through their planning and research funds, could potentially be a significant resource. AURORA has already been formed as a pooled-fund consortium of several states, primarily focused on road/weather concerns.

The public-private relationships are also a challenge. At present, NWS maintains a system of public weather information oriented toward safety and productivity. Its active alliance with aviation fulfills its legislated mission to serve "navigation." There is no comparable service for "commerce," which historically has meant surface transportation.

There are geophysical reasons for this. Weather-threat information on the ground and specific to roadways, tracks, or canals involves air-land-water interactions of a type and scale only now achievable by observational and predictive capabilities. As a result, value-added meteorological services (VAMS) have stepped in to fill the gap in "tailored" information for surface transportation operators and users.

The open-system concept, allied with advances in the technology of environmental prediction and communications, is a key to the issue of informational integration. An "open system" technically means that the entire information system from sensors to graphical prediction displays has a common structure (architecture) and publicly known ways of connecting each component of the architecture (standards). An open system is necessary to achieve the decision-support capability that is the linchpin for coordinated action within the transportation system. Open systems convert the proprietary conduits of information to a network of complementary, but also competing, information processes.

Photo of a Differential Global Positioning system

New alliances are being forged between meteorology and the transportation communities. Differential Global Positioning Systems, such as this one, being deployed by U.S. DOT and other agencies also serve to measure atmospheric water vapor. Technology increases the need for joint research on better weather information and its applications.

As the national weather-information system shows, shared observations are essential to good predictions. Some assimilation applications require an open system to access all observations. Today, many weather-prediction models, including those that must operate on a small scale, provide useful resolution. These need to network with the observations, other predictive processes (such as deriving road temperature from weather prediction through heat-balance modeling), the NWS models (for national boundary conditions), and potentially with each other (to create prediction ensembles that are better than individual predictions). With an open system, VAMS can produce better products and reach a larger market.

Over time, with the appropriate research to identify the gaps in the delivery of crucial information to decision-makers and to improve the performance of the whole system, a new public-private allocation of services will emerge.

The ITS program, through the National ITS Architecture and its standards, has championed open systems in surface transportation, and emulates what is largely an open system on the weather side under NWS auspices.

A Research Agenda

This is the time to work out the details of a research agenda. The main targets of research, as outlined in Table 2, are clear.

The agenda relates to, but goes beyond, the concerns of existing research and focuses specifically on application to surface transportation. The agenda contains a lot to do for everyone — universities, national research laboratories, states, and private firms. The conduct of the agenda should follow the model already established for highway research, which involves all of these organizations.

However, the program needs a federal focus. Because of the effective public-private system of weather information in the United States and the strong intermodal interests, the inter-federal alignment in the program needs to be even stronger than in the Federal-Aid Highway Program. A federal focus within DOT is necessary to conduct the inter-federal coordination and to mobilize coordinated efforts among the local and private constituencies.


The Federal-Aid Highway Program, first authorized in 1916, was preceded by two decades of research and organizing stakeholders. During this period, many state DOTs were created. An equal period of research and development preceded the Federal-Aid Highway Act of 1956 that created the Interstate Highway System and the Federal-Aid Highway Act of 1962 that required comprehensive urban transportation planning.

In this era of "Internet-speed," research still needs the commitment to a long-term vision, planning of programs, and development of constituencies. The research program must harness public, academic, and private partners to apply advanced weather information and decision support to open-system products that serve operational techniques.

The result will be a continual evolution of information and operational responses to weather. Research on an open system will create new informational services and uses that are barely imaginable now. The payoff is going to be in the efficiency, safety, and security of our surface transportation system that carries the bulk of travelers and commerce.


1.Richard F. Weingroff. "A Peaceful Campaign of Progress and Reform: the Federal Highway Administration at 100," Public Roads, Vol. 57, No. 2, Autumn 1993.

Table 2 —Transportation Weather Research Targets and Activities

Target Associated Research

An open and national surface transportation observation system integrated with the international environmental observation system.

  • Improved surface sensors.
  • Mobile sensing.
  • Remote sensing.
  • Sensing platform investment and siting guidance as part of the national information infrastructure.

Timely, accurate, and relevant transportation condition prediction.

  • Basic research in subsurface-roadway-air geophysics.
  • Assimilation techniques for transportation observations.
  • Improved detection and prediction of surface-level precipitation form.
  • Prediction-model ensembling.
  • Specialized models for surface-attribute prediction.

Decision support for coordinated action on all surface transportation weather threats.

  • Data source fusion.
  • Risk decision-making.
  • Collaborative decision-making.
  • Human factors in display and information use.
  • Adaptive learning systems.

Operational management tools and techniques to make use of weather threat decision support.

  • A fundamental operations research effort to understand and quantify management functions.
  • Advanced maintenance technologies.
  • Integration of weather information into traffic management.
  • Integration of weather information and traffic management into emergency management.
  • Improved air pollution prediction and response.
  • Improved dispersion/exposure prediction and response to transportation hazmat (accidental and terrorist) incidents.

Traveler and vehicle-operator support for coping with weather threats.

  • Local hazard warning — media and messages.
  • Use of national driver simulation to test response to weather threats.
  • Human factors — behavioral, risk, and distraction.
  • Vehicle speed and platoon dynamics under weather conditions.

Improved knowledge of the causal relationship between weather and surface transportation goals and the effectiveness in improving goal performance.

  • Long-term project evaluation (to control for climatic variability).
  • Macro-scale economic evaluation of weather effects on commerce.
  • Augmented crash data and analysis for weather factors.
  • Operations research of management functions to identify costs and savings.
  • Research on road chemical dispersion and environmental effects.

An evolving open network of all information processes connecting weather to surface transportation decisions.

  • Standards for transportation weather data and display objects.
  • Continuing evolutionary development tracks.
  • Network survivability.
  • Integrated architectures.

Gary G. Nelson is an intelligent transportation systems (ITS) planner and systems engineer at Mitretek Systems Inc. in Washington, DC. He has more than 30 years of experience that combines planning and system engineering in the surface and air modes. Work on the national air traffic management system, including aviation weather, led to a contract to support of the FHWA Road Weather Information Program.

Nelson has a master's degree in engineering and has completed some additional study at Rensselaer Polytechnic Institute in the doctorate program in computer and systems engineering.

Rudy Persaud is a highway research specialist in FHWA's Office of Operations Research and Development at the Turner-Fairbank Highway Research Center in McLean, Va. His primary responsibilities are in the fields of road weather management, rural ITS, and the global positioning system (GPS). Previously, he worked for South Dakota Department of Transportation. He was in charge of the state's local road system, and he implemented the GPS and geographic information system (GIS) program for all roads in South Dakota. Persaud has a bachelor's degree of science and technology in road construction from the University of South Dakota.




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