Information Systems

Mirroring the nation’s continuous march toward technology, the battle against snow and ice is increasingly being fought as much with microprocessors, sensors and computer monitors as with shovels, salt and sand.

At the same time, de-icing is taking a back seat to anti-icing – the application of chemicals before snow and ice bond to the pavement, an action that requires far smaller quantities of chemicals and may reduce salt usage.

Anti-icing, which involves applying chemicals such as liquid magnesium chloride, liquid sodium chloride and potassium acetate, relies heavily on the computers and pavement sensors of road weather information systems (RWIS) for its effectiveness,

This preventive technique is a far cry from the conventional way of doing things. Under the old scenario (one that has not, and probably won’t be, replaced entirely, experts say), if it looked like it was going to snow, driv-ers of plows and salt spreaders were kept on duty, and when the snow began to fly, were sent out to do battle with the elements.

“That system uses a lot of labor and materials such as salt and sand,” says Rob Fox, product manager for Seattle-based Coastal Environmental Systems, an RWIS manufacturer. Moreover, concern is mounting about the damage salt does to the environment, fish and wildlife, infrastructure and vehicles.

The use of an outside forecasting service is a third modern-day option or snow and ice control. These companies can provide localized snow and ice forecasts to municipalities, airports and state highway departments – with or without a complementary RWIS – to aid anti-icing campaigns.

One such firm, AccuWeather, State College, Pa., provides forecasting, graphic displays, maps and data to about 300 municipal public works departments (including Washington, D.C.) and 12 state departments of transportation.

Spawned by istea

RWIS, one component of the broader array of intelligent transportation systems spawned by passage of the Intermodal Surface Transportation Efficiency Act in 1991, has been around a few years but has seen wider use in Europe and Japan until recently. Its use in the United States is on the rise because of a proven track record. “The push is definitely on,” says APWA’s MacMullen.

In 1993, a task force assembled by the Minnesota Department of Transportation to study RWIS technology concluded that RWIS is necessary for an effective anti-icing program and that it improves the accuracy of event forecasting, which has a direct impact on the scheduling of crews.

Further, the panel concluded, RWIS data greatly enhance the National Weather Service’s ability to issue timely winter storm warnings in areas that do not have weather reporting stations.

RWIS configurations can vary, but they typically include a small roadside weather station with a remote processing unit (RPU) that is mounted on a tower and connected by cable to pavement sensors both above and below the surface.

The weather station, which measures such factors as wind speed and direction, temperature, humidity and barometric pressure, communicates with a central processing unit (CPU) either through the telephone lines or by radio waves.

The pavement sensors measure surface and subsurface temperatures, percentage of chemicals in an anti-icing solution and the presence of ice on the roadway. The data warn of adverse road conditions, predict the onset of icing and help maintenance crews determine the best course of action.

“I think these systems definitely improve safety, and they save states money by helping them to deploy their resources more efficiently,” says Fred Kitchener, project manager for the Idaho Storm Warning Project, an ITS operational test of existing and emerging technology.

The project is designed to equip the Idaho Transportation Department with up-to-the-minute data on reduced visibility conditions, which the department can in turn disseminate to motorists in an attempt to reduce multi-vehicle accidents.

A 100-vehicle pileup on northbound I-75 in Tennessee seven years ago that killed several people and injured scores of others is a dramatic example of the type of accident RWIS can help prevent, Kitchener says.

Tennessee has since installed fog warning equipment on the stretch of road where the accident occurred, a low-lying, swampy area with frequently poor visibility.

Some cities – Seattle being a prime example – have a dire need for RWIS because temperatures and road conditions can vary dramatically from one section of town to another. “You could have a 12- to 15-degree difference in different parts of the city,” Fox says.

This is because of the “convergent zone,” where fronts coming off the Pacific Ocean divide over the mountains then join together again; Arctic cold fronts can also swoop down and stir up the pot.

Kansas City, Mo., has used RWIS for several years and found the technology to be highly successful, according to Larry Frevert, deputy director of public works.

In the late 1980s, the city approached the Missouri and Kansas departments of transportation about developing a cooperative agreement to reduce the initial expense of creating a RWIS and allow for future expansion.

Under the agreement, each government agency purchased its own RPU, and an RWIS manufacturer, St. Louis-based Surface Systems, provided a CPU at cost. Additional RPUs have since been added, and the cities of Overland Park and Lenexa, Kan., have also joined the system.

Kansas City’s need for site-specific pavement forecasts was dire, Frevert says, since it is located where the Missouri and Kansas rivers join together, creating misty or foggy conditions in some areas. The terrain is also uneven, and about 400 bridges cross the rivers.

With several years of RWIS data collection and analysis experience under its belt, Kansas City is enthusiastically embarking on a methodical anti-icing program with formulaic policies on which types of roads receive which types of chemical treatment, under what conditions and by which personnel.

“Anti-icing is the most exciting thing [in snow and ice control] that I have seen come along in quite a long time,” Frevert says.

Increased usage

Although a considerable number of large municipalities and airports use RWIS, it can be a hard sell when it comes to smaller communities.

“The people in Idaho were initially unsupportive,” Kitchener says. “Now they’ll tell you they can’t live without that information.”

Adds Fox, “The biggest hurdle to jump over is that it demands a complete change in thinking.”

The movement toward greater compatibility of different systems, with open hardware and software architecture, is bound to make RWIS more affordable and accessible, Fox contends.

In addition, the federal government is much more likely to help fund RWIS projects now than in the pre-ISTEA days, says Fox.

Regardless of how a RWIS is set up, cooperation and communication between different government agencies, as practiced in Kansas City and other municipalities such as Washington, D.C., is a key to success.

In cities located near bordering states, the highway departments of proximate states might share their information with other entities including parks departments, airports, public transit agencies and city public works departments.

Such pooling together of information is becoming increasingly common, according to MacMullen.

Add potholes to that list of life’s certainties, right alongside death and taxes. Potholes have proved to be a recurring problem as patches designed to fill them invariably break apart after a few weeks or months – especially in northern cities.

But a better way to deal with potholes is on the horizon, thanks to the Oak Ridge National Laboratory. Terry White and Tim Bigelow, researchers at the Oak Ridge, Tenn.-based lab, are developing a machine that uses microwaves to repair potholes and cracks. It works by heating both the asphalt patch material and the area to be fixed, resulting in repairs that are seamless and much stronger than those done by merely compacting hot asphalt into a hole, the researchers say.

The new technique, which may be on the market in two to three years, also serves as a trouble-shooter, seeking out potential pavement problems before they become visible on the surface. Using radar-like techniques that send a signal beneath the surface, the device can detect cracks and flaws beneath asphalt and concrete.

“By scanning the antenna along the asphalt surface, we can look for changes that indicate underlying problems that may not be visible on the surface,” says Bigelow, a member of the lab’s Fusion Energy Division.

The microwave repair technique in development at Oak Ridge could be used with a hand-operated applicator or scaled up to a high power truck-mounted system, according to the researchers. The microwave technique could also be used to seal joints between old and new material, making for seamless repairs when utilities have to be installed or between highway lanes that are paved individually.

Repairs can also be made using cold material, saving the expense and trouble of hauling heated asphalt to the potholes. And repairs can be made year-round instead of mainly in the warmer months.

Bigelow and White say they plan to do field testing and gather lifecycle costs to support their contention that microwave asphalt repair has economic advantages.

“Small-scale applications would provide the quickest payoff,” Bigelow says. “[But] we need support from the paving manufacturers and highway maintenance organizations to gather information about larger scale use of this technology.”

The research, a spin-off of a microwave decontamination process White developed, has been funded by the Department of Energy’s Office of Technology Development and with Oak Ridge discretionary funds.

In past decades, stream stabilization was a fairly cut-and-dried process: the waterways were merely lined with concrete. In Fairfax, Va., for example, a 1970 study had recommended that measure for the city’s streams, although lack of funding prevented its implementation.

But times change. And when Fairfax residents approved a $2 million bond issue in 1994 targeted at stormwater system improvements, the city finally had the necessary capital to counteract the negative effects of urban development on its drainage system.

In reviewing its stormwater problems, the city determined that stabilizing area streams would be the most effective and economical first step. After researching new and innovative approaches to stream restoration, the public works department saw that bioengineering and stream morphology would be key in the effort.

In meetings to introduce the concepts of stream restoration and stabilization to area residents, public works staff provided an overview of the design philosophy and various stream stabilization measures. Citizens could view preliminary construction plans showing details of what was proposed along their properties, and could also see before-and-after slides of similar stream stabilization projects.

This process enabled the residents to actually see how the proposed improvements would enhance the stream channel. Individual meetings with property owners were also conducted whenever requested.

At the citizen meetings, the public works staff introduced the idea of re-establishing a natural buffer around the streams, showing residents how they could participate in the project by providing a natural, unmowed buffer on any land adjacent to the stream channel. To ensure success, it was important to sell the concept to area residents, since many of the city’s stream channels flow between residential properties. Once educated on the benefits of the proposed stream stabilization methods, the majority of residents were thrilled with the idea of using natural plant materials to stabilize the banks.

This groundwork prior to construction meant that the city received very few complaints or questions during the construction phase.

The public works department chose a stream section between two major city roadways, with an adjacent trail as a demonstration area. Various methods of stream stabilization and restoration were used, including rock vortex weirs, bio-logs, root wads, vegetative plantings and stream realignment.

To ensure survivability of the plant material and to blend it with adjacent areas, the city used native plant material. Since the plant material will take several years to mature to its desired growth level, the stream stabilization measures were designed to protect the banks during this growth period.

The major criterion for plant material in the project was the ability to produce a large enough root mass to ensure streambank stabilization. In those areas where the plant material was considered insufficient to provide the necessary stabilization, the public works department installed more hard-edged measures incorporating rip-rap.

The city plans to use educational signage and citizen seminars to publicize the demonstration area and further teach the community about the benefits and various methods of stream stabilization and restoration. Grant funds received from EPA under the Chesapeake Bay Program will finance the signs and initial seminars.

To date, the city has completed stream stabilization and restoration work on approximately 2.5 miles of area stream channels. While voter-approved bonds funded the initial stages of work, two cents of each dollar that the city collects in property taxes is now allocated for further design and construction of stormwater improvements.

This article was written by Adrian Schagrin, city engineer in the Fairfax, Va., department of public works.