Stopping accidents cold
The feeling of tires slipping on a patch of black ice, sending the vehicle into a skid, is one of the worst a driver can have, and transportation departments around the country are turning to technology to help prevent that dangerous situation. Particularly in cold climates, where ice can form quickly on bridges during winter storms, public works crews are installing permanent anti-icing systems to stop ice from forming and reduce the need for road crews to drive out to treat common problem areas.
Some systems are designed to spray anti-icing materials onto the road when triggered by temperature sensors or by remote staff in a central office. Others consist of layers of material applied to the road surface to retain anti-icing chemicals. Depending on the size of the project, costs for the systems can be high, but they can save drivers considerable amounts of money by preventing accidents. “They are very cost effective because they save lives early in a storm when the driver doesn’t even realize the roadway is icy,” says Richard Hanneman, president of the Alexandria, Va.-based Salt Institute. “The first accidents occur when people aren’t aware that the rain they are seeing is hitting pavement that is below freezing and creating black ice.”
Fixed Anti-icing Spray Technology (FAST) systems have been widely used in Europe since the 1980s and in North America since the late 1990s. They consist of a series of pumps, pipes, valves and nozzles mounted on a bridge, railing or directly in the pavement to spray anti-icing materials at a pre-determined rate and pattern onto the bridge or roadway. The systems are either automatically triggered by pavement sensors that detect moisture on the roadways and a temperature below 32 degrees, or they can be remotely triggered when a sensor sends a signal to a central office indicating freeze conditions.
The Montana Department of Transportation (MDT) installed a FAST system in October on a ⅛-mile stretch of the West Laurel Interchange, an eastbound bridge on Interstate 90 about 10 miles east of Billings, Mont. “When the bridge was constructed 40 years ago, the design standards were such that it has more of a curve than a bridge on an interstate would have today,” says Craig Abernathy, MDT experimental program manager. “When you add ice to that, drivers overreact, and we’ve had a high level of crashes there due to ice.”
Although MDT is only just beginning to study the system’s performance, Abernathy is optimistic about the potential benefits. If it finds positive results after a 60-month evaluation period, MDT could install additional systems elsewhere.
The New Jersey Department of Transportation (NJDOT) is in its second winter of monitoring a FAST system installed on a nearly one-mile stretch of Interstate 78 in the Jugtown Mountain area of Bethlehem Township. The system covers a bridge and the approaches to the bridge in both directions. “We had a high number of wet weather accidents there due to ice. It is in an area that, for New Jersey, is a higher elevation,” says Richard Shaw, NJDOT director of operations support. “When the weather moves through quickly, we get a lot of icing there when we don’t get it in other places in the state. It made sense from a wet weather point of view to put the system there.”
The fully automated system can be triggered from the nearest maintenance yard or regional control center and, so far, has performed well. Although the $2.2 million system is not saving the state money in its budget, Shaw says there are safety benefits. “We have seen a significant drop in the number of accidents in that area since the system went into place. The savings is to the public in damage to vehicles and human life. This is mainly a safety issue,” he says.
Layers of safety
More recently, researchers at Michigan Tech developed the SafeLane system, which consists of a layer of epoxy covered with a limestone aggregate material spread onto a bridge or roadway. After the first layer cures, a second layer of epoxy and aggregate is added. Once the material is in place, anti-icing chemicals are sprayed onto the overlay. The chemicals trickle down into the aggregate, which serves as a “rigid sponge,” and are held there until surface moisture and low temperatures activate them. Additional chemicals can be added after an ice or snow storm to replace any depleted materials.
Wisconsin has the oldest application of the SafeLane system in the country. Installed in 2003 on the 135-foot Wolf River Bridge on U.S. Hwy. 8 in the northeastern part of the state, it is now in its fourth winter of service. “The number of ice-related crashes we are aware of at that site has gone down to zero since the installation,” says Tom Martinelli, winter operations engineer for the Wisconsin Department of Transportation. “We check for accident reports at that location and have not found any. And, as the local maintenance supervisor has told me, prior to the overlay installation, every spring they had to send a crew out to repair the beam guard at the bridge damaged by people skidding into it, and he has not had to do that once since this system was installed. That’s how he measures it as a success.”
In 2005, the Wisconsin DOT installed the system on an approach ramp to the Blatnik Bridge in Superior, Wis., a large span that connects the city to its neighbor, Duluth, Minn. And, in 2006, it treated another bridge on U.S. Hwy. 53 south of Superior that also had a history of ice-related crashes. As a result, the DOT’s anti-icing trucks do not have to treat those bridges as often during the winter. “We are only treating the SafeLane installations once a month with our mobile operations, where we might be treating them weekly if they did not have the icing overlay,” Martinelli says. “The up-front cost is more, but what we are really monitoring now is how long it is going to last. If we get 10 to 15 years out of it, economically that is a savings. Compared to typical winter maintenance activities, you are putting less material on the road, you have less man hours to maintain it, so there is an overall cost savings benefit.”
The Minnesota DOT (MinnDOT) has installed FAST and SafeLane systems, and both have resulted in fewer crashes at problem spots. “We have a major corridor highway, Interstate 94 connecting Minneapolis and St. Paul, which carries 150,000 passengers a day,” says Gabriel Guevara, a maintenance operations engineer for MinnDOT. “In the past, we had accidents of such magnitude there that the losses were tremendous. Since we have installed the FAST system there, we haven’t had a problem like that due to snow and ice conditions.”
There are seven fully automatic and four semi-automatic FAST systems installed around the state, and DOT officials are considering at least six more sites for installations. The state’s most expensive, on a bridge over the Minnesota River, cost more than $1 million. “FAST systems are not 100 percent trouble-free. You need ongoing operation and maintenance of the systems, and some installations are very expensive, but we are sold on it. We do think there is a place for systems like this,” Guevara says.
After SafeLane was applied to the westbound lanes of the Marshall Bridge near Hibbing, Minn., the ice-related crash rate decreased to zero. The eastbound lanes were left untreated as a control. “Every highway is inherently dangerous because people use it,” says John Bray, special assistant to the Northeast District Engineer for MinnDOT. “If we can make a roadway safer and give motorists a second chance where they might not have had one before, then that is a good thing.”
Although installing the SafeLane product is labor intensive — crews hand spread the layers of epoxy and aggregate, which are then smoothed out by a grading machine to remove excess aggregate — Bray says it requires little maintenance other than the periodic application of sprayed-on anti-icing chemicals before winter storms. “When you get icy conditions, this stuff begins to work immediately,” Bray says. “You don’t have to dispatch a truck and employees to take care of the problem, so you dramatically add to the safety of the motorists.”
The SafeLane system, marketed by Minneapolis-based Cargill, is expensive — about $9 per square foot — says Steve Giese, operations manager at the Indiana Department of Transportation’s Plymouth sub district, but in dangerous places, it can be worth the cost. “This season we have had heavy snow and conditions of six below zero when every stretch of road iced over, and I mean everywhere, except for [the bridge treated with SafeLane],” he says. “As for savings, this doesn’t save me money, but it saves me accidents. If I can get 36,000 vehicles over that bridge in an ice storm without any crashes, it’s worth its weight in gold.”
As highway departments consider their options for keeping roads clear in the winter, many more may find new uses for permanent anti-icing systems. “We are a mobile society, and having snow and ice on the roads changes everything,” Hanneman says. “It destroys the economy, it disrupts personal lives, it prevents people from getting to work, and it hinders fire and police response, among many other problems. The snow-fighting budget is often the largest expenditure of local governments in the snow-belt region — other than schools. Those are the reasons why governments spend a lot of money doing it, and that is why it should be done well.”
Maria Lameiras is an Atlanta-based freelance writer.