'Dragnet' system replaces runaway truck ramp
SUE MYERS Star-Tribune correspondent | Posted: Saturday, December 11, 2004 12:00 am
BUFFALO - A tractor-trailer loaded with pipe for the Campbell County oil fields heads down the mountains on U.S. Highway 16 just above Buffalo. The driver remembers the steep grade ahead and gears down as he passes the "check brake" turnoff, then touches his brakes for reassurance.
They don't respond.
He pumps frantically; still no response. Adrenaline rushes through his body. His grip tightens on the steering wheel. He knows what he must do.
He gets through the first sharp curve but feels the truck gather more speed as he starts down a short straight stretch. Ahead is a sign - "Runaway Truck Ramp, 2 miles" - and another sharp curve to maneuver.
He concentrates on keeping the truck under control as the speedometer nears 80 mph. He watches for the signs: The ramp is 1.5 miles ahead, then half a mile ahead. He peers past the "500 feet ahead" sign and sees arrows pointing into a concrete passage.
What in the *@#!^&* is this?
He has no choice: He takes a deep breath and heads for the gap.
In seconds, the truck is stopped. The driver shakes his head in disbelief. He doesn't understand what just happened, but he breathes a quiet prayer of thanks and steps down from the truck.
That scenario could soon unfold on the steep stretch of Highway 16. The Wyoming Department of Transportation has installed the state's first "catch system" or "dragnet," an innovative alternative to the runaway truck ramp previously used there.
Something different
Paul Johnson, resident engineer with the WyDOT in Buffalo, said the previous runaway truck ramp was designed, as are most, with an uphill ramp ending in a windrow of loose gravel in the middle to absorb the impact energy of a runaway truck.
"This worked fine for a lot of years, saving a number of lives with little loss of property," Johnson said, "but there was always a safety concern because the ramp was on the north side of the highway. This meant the driver of a runaway truck had to cross oncoming traffic to reach it."
When it came time for the reconstruction project on that stretch of Highway 16 in 2003, WyDOT formed a value engineering team to research options to eliminate the danger. Among the options was putting a bridge over or under the highway at that point, but the final decision was to install a catch system or dragnet.
"This seemed to be the most feasible in regard to maintenance, ease of use and effectiveness," Johnson said.
Originally designed in France for use in the Alps, only two such dragnet systems exist in the United States - one is Massachusetts, the other in Hawaii. According to Johnson, the one installed here is the "heaviest duty," as the others use a combination of gravel and nets.
Ames Construction, the project contractor, submitted a bid of about $226,000 for the first phase of reconstruction and its crew was in charge of all the preliminary work. The first step was to build two sets of retaining walls to support the structure, with a total of 176 "steps" or elevation changes. The ramp itself consists of a 1,000-foot concrete slab with concrete side walls about 4.5 feet high and a 14-foot-wide entryway.
When it came time to install the net system itself, representatives of Impact Absorption Inc., the system manufacturer out of New York, were on hand. The truck arrester part consists of a series of nine nets. Each net is attached to four energy absorbers. Each energy absorber is a chamber enclosing 200 feet of coiled steel tape. When a truck hits a net, the coiled tape is pulled through a series of offset rollers. Thus, the impact energy is slowly absorbed by friction and the deformation of the metal tape.
Each energy absorber provides 4,800 pounds of resistance to the impacting vehicle, resulting in a slowdown of 16 feet per second.
Johnson said the company representatives also trained the local WyDOT maintenance crew on how to replace the net system after use. He said the cost for replacement will run the trucker's insurance company between $60,000 and $70,000.
The runaway truck dragnet, along with an advance warning system and a series of warning signs, became fully functional in mid-November. About three miles above the dragnet is a large sign, "Runaway Truck Ramp in Use When Flashing," which is also attached to a dedicated phone line that automatically alerts the sheriff's office.
Just below that is a "check brakes" turnout area. About 2.5 miles above the dragnet begins a series of warning signs, including "Steep Grade 7%," "Sharp Curves," and several indicating how far ahead the runaway truck ramp is. Melissa Butcher, WyDOT information officer, explained the term "ramp" rather than dragnet was used because most drivers are not familiar with the dragnet system.
Will it work?
WyDOT officials say they realize it will probably take time before truckers have faith in the new system, and a few things need to be ironed out, such as improving the visibility of the entryway.
Independent trucker Dave Owens of Sheridan, who often hauls heavy loads of logs on Highway 16, said all he really knew about it was what he saw.
"It looks very dangerous to me - like those cables could shred the front end of a truck and cause more damage than the old ramp," he said. "But you do worry about crossing traffic to get to the old one."
John Buckingham of Buckingham Lumber Co. said he was also unfamiliar with the new runaway truck ramp, but expressed faith in the device.
"If you're coming down that mountain and you know you're in trouble, you have to assume it's workable," he said. "It gives you hope so you don't have to do something like hit the wall or bail out."
According to Johnson, runaway truck ramps are not used all that much any more because the brake systems on trucks have been vastly improved over the years.
"But," he said, "there's always that chance. Just a month or so ago, a semi used the old ramp, went all the way to the top and had to be towed off. I would have asked him why he didn't use the new one, but he didn't speak English."