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February 2002

Keeping traffic on the move: RAP project focuses on winter highway maintenance

What a hole-in-one is to a golfer, the correct application of chemicals on an icy road is to a winter highway maintenance crew. The goal is to apply just enough salt and other substances to keep the roads clear, but not an excessive amount that would cost unnecessary money and additional environmental harm.

Bill Mahoney (inset) and other RAP scientists are working on a U. S. Department of Transporation-funded project to keep winter roads clear. (Photos by Carlye Calvin.)

But perfection in road maintenance, as in sports, is a difficult standard. Highway officials frequently have to determine road conditions by weighing complex and often conflicting reports about weather forecasts, road conditions, and traffic from a battery of computer monitors—a less-than-airtight technique informally known as "swivel chair integration."

Add to that the additional complexities of applying various chemicals (sodium chloride, magnesium chloride, and calcium chloride) at a time of increasing environmental concerns, and choosing between such strategies as anti-icing (preventing ice from forming), deicing (removing ice after it forms), sanding, and plowing.

Enter RAP. Bill Mahoney and other RAP scientists are working on a U.S. Department of Transportation–funded project that aims to coordinate data about weather forecasts, road surfaces, and traffic patterns. The goal is to ensure that highway officials have the best available information to make winter maintenance decisions.

"We plan to prototype a system that brings all of the information together—surface and subsurface characteristics of roads, locations of bridges, consensus forecasts from multiple models, precipitation type, and more," Bill says. "It will allow highway officials to be much smarter about current and predicted road conditions."

If all goes as planned by the Federal Highway Administration, the new system eventually will be supplied by private vendors and deployed by state transportation departments.

The project, known as the Maintenance Decision Support System, may portend a new direction for meteorology. Whereas forecasters have spent decades focusing on atmospheric events that can affect aviation, only recently have they begun to home in on "road weather"—the effect of weather changes on particular stretches of pavement.

But weather, arguably, has as great an impact on road transportation as on air and sea transport. With the proliferation of two-car families, the construction of an ever-growing network of roads, and the economy’s increasing reliance on trucks (which handle more than 80% of the nation’s freight, according to the trucking industry), Americans are highly dependent on good driving conditions.

"If we can improve weather prediction and maintenance for our highways, the cost-benefit ratio for the national economy can be 10-to-1," Bill says.

Improving safety is another major consideration in keeping roads clear of ice and snow. According to the Department of Transportation, more than 17% of fatal crashes occur during severe weather conditions.

The prototype will draw on existing high-resolution numerical forecast models, which will be coupled with information about road characteristics (such as which roads are asphalt and which are concrete). Ensemble forecasts and precipitation-type algorithms, as well as data about road temperature and friction, will be incorporated into the prototype.

The Federal Highway Administration hopes to achieve "better transportation performance." An administration summary of the project states: "It is clear that substantial benefits can be realized if weather forecasts and road condition predictions are improved, more specific, more timely, and tailored for surface transportation decision makers."

Bill emphasizes that RAP is assembling existing capabilities for the prototype, rather than trying to build new technology. "We’re taking what we can off the shelf to expedite the development process," he explains.

RAP is the lead technology agency on the project, with a team that includes Ben Bernstein, Jim Cowie, Bill Myers, Claudia Tebaldi, Jamie Wolff, Jaimi Yee, and Greg Young. Other participants include the U.S. Army’s Cold Regions Research and Engineering Laboratory, the Massachusetts Institute of Technology’s Lincoln Laboratory (an Air Force facility), and NOAA’s National Severe Storms Laboratory, Environmental Technology Laboratory, and the Forecast Systems Laboratory.

A complex challenge

RAP plans to debut a functional prototype in April to a small group of transportation officials. Scientists will apply weather and road data to an actual storm that took place during the winter in Minnesota and begin evaluating how accurately the system’s data predicted weather and road conditions.

The team then plans to fine-tune the usability of the system and demonstrate a working prototype next winter.

Bill cautions that the system is unlikely to be 100% effective because it is difficult to predict precipitation type and pavement temperature along particular stretches of road. But RAP’s goal is to help maintenance crews make decisions about the types of chemicals to apply, as well as where and when to begin the application. If a forecast calls for heavy precipitation along a north-facing section of road on an unusually cold day, for example, crews might do better to apply sand instead of salt. That’s because salt cannot melt ice in very cold temperatures, but the sand can still provide traction.

Another strength of the Maintenance Decision Support System is that it will allow decision makers to manipulate the data in order to prepare for a variety of scenarios, such as unusually heavy traffic along a designated highway.

Bill emphasizes that the three-year project is just "scratching the surface" of forecasting for surface transportation. But it may pave the way for far more research into the effects of weather on roads, as well as on other surface transportation systems, such as railroads.

"We’re just basically taking baby steps to show the potential benefits of bringing all these things together," he says. "If we can excite the users, such as highway officials, then it’s much more likely that there will be more road dollars in the future."

•David Hosansky

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Edited by David Hosansky, hosansky@ucar.edu
Prepared for the Web by Carlye Calvin
Last revised: Fri Feb 22 17:08:40 MST 2001