This almost never happens on Teton Pass in the summer: Traffic stopped flowing around 10 a.m. Without the sounds of RVs and a cavalcade of cars the vast stillness of the mountains settled over the Tetons’ southern slopes.
A radio call broke the silence: “OK, he’s coming down.”
A yellow dump truck loaded with heavy, wet sand rounded Talcum Powder Corner — named for a pair of crashes that dusted the highway — above the runaway truck arrestor. Entering the straightaway, it gained speed, hurtling downhill toward the structure, which is built to catch a 90,000-pound truck going 90 mph.
Veering right toward the mouth of the arrestor, the truck continued accelerating, 60,000 pounds looking very much like the out-of-control rig that is the nightmare scenario on the steep pass.
The crash split the silence like ordnance as the truck went through the first net, ripping it off. The next three nets blanketed the grill. Steel tapes extended, attached to canisters on the wall, pulling speed from the truck and stopping it within about 100 feet; as it ground to a halt, a wave of sand erupted from the bed, cascading over the cab and along the arrestor.
The crash was not an out-of-control driver reacting quickly in an emergency, but a Wyoming Department of Transportation test of the redesigned arrestor, which underwent a facelift after a high-profile failure. In catching the dump truck last week, the updated arrestor passed its first test.
Truck arrestors, which dot mountain passes all over the world, employ a series of steel nets to stop runaway vehicles without sending drivers through windshields. Their two jobs are to stop trucks — avoiding damage to other cars and homes along the road — and to prevent major injury to drivers.
In WYDOT’s July 13 test it was immediately evident the first goal was accomplished. As for the second objective, WYDOT officials and representatives from the manufacturer waited in silence in the moments after the truck came sliding to a stop. Watching from the end of the arrestor or the hillside across the road, they looked for the driver to indicate he was OK.
Inside the cab, Arnold Korbmacher, a professional driver, moved his head encased in a full-face helmet (the truck had no airbags). Then he removed the helmet, opened the door and stepped out.
The crowd exhaled a sigh of relief, bursting into applause. With Korbmacher’s appearance, the arrestor had officially passed its test.
It didn’t work before
WYDOT opened the truck arrestor in March 2017. It replaced the runaway truck ramp just downhill on the opposite side of the road. To use it, truck drivers had to cross traffic, which any commuter knows is pretty much constant these days.
That meant in an emergency situation a trucker would have to make a split-second decision, and in bad traffic a driver might choose to ride it out toward Wilson.
“If there are a bunch of cars there, you probably won’t cut across,” WYDOT Director Luke Reiner said. “If you do, you could kill a family on vacation.”
Neither option was palatable to WYDOT officials, so they installed the arrestor. The basic design included sets of steel nets strung across the concrete structure.
The nets were attached to canisters that held steel tapes that extended as a truck pulled on them. If the truck was going too fast it would rip them out at the end of the line, and another set of nets at the end would repeat the process.
The system caught several runaway vehicles in its first two years, but a September 2019 accident revealed the design’s limitations. A pickup towing a trailer with 32 logs as cargo veered into the arrestor after its brakes failed.
Instead of being caught by the arrestor, the truck blew through it, taking out every net before jackknifing at the end and nearly tumbling down the hill above Trail Creek Road. Investigations revealed that the truck hit the canisters, shearing them off the wall and snapping some of the steel tapes.
Though the driver walked away without major injury, that incident lent urgency to addressing the problems.
“For me, it’s like, ‘Hey, this has to be no failure,’” Reiner said. “We have to have confidence that it works. Otherwise, we got to go do something else.”
WYDOT went back to the manufacturer, Impact Technologies, to devise a new system that wouldn’t let the canisters be torn off.
“If they aren’t anchored, they can’t work,” Reiner said.
A secondary problem in the original design was the fixed attachment point for the canisters. They could move right to left, but not up and down, so when the steel tapes extended, downward force on the canister had the potential to shear the tape, rendering it useless.
Over more than a year and a half, Impact Technologies and WYDOT retooled the design and tested the components. While they worked on a longer-term solution, WYDOT put a sand barrel array in place last summer, the field of plastic barrels intended to keep cars from sailing all the way through.
To address the issues, Impact Technologies hired Michael Brackin, a structural engineer from Texas who said companies call him to “fix problems.” They came up with two simple-sounding but technically complex solutions that cost WYDOT around half a million dollars, engineer Bob Hammond said, with the company kicking in a comparable amount.
First they built “bump outs” that protect the canisters, triangular housing that pushes a vehicle off the wall as it passes by the nets. In the test they proved their worth: Korbmacher had hoped to drive straight through the middle, but his front right tire went flat and he was pulled into the right-side wall.
As planned, the bump outs kept the canisters affixed to the wall as he passed by them.
The second concern took reengineering of the canister attachment point.
“What we made was a little bracket that lets that canister rotate up and down instead of just left and right,” Brackin said. “That was probably the biggest thing.”
After all that, nearly two years after the log truck blew through the original design, Korbmacher gave WYDOT and Impact Technologies proof of the new concept, as the 60,000-pound truck going 60 mph stopped within just a few feet of where they calculated it would.
Was that a relief to Impact Technologies owner Michael Kempen?
“I’m happy, to be honest with you,” he said. “I’d like to get more excited, but it’s been a 20-month haul.”
Proof of concept
Part of the palpable anticipation at the test was the novelty of it.
The components had been lab-tested, Brackin said, but for the new design there was no way to test it other than live on-site. So when you need someone to drive a fully loaded, speeding truck, you call a professional.
Korbmacher lives in Bellingham, Washington, and the former Mount Baker ski patroller works contract driving jobs. He might be the person driving a stunt in a video or behind the wheel in a car commercial.
The truck arrestor test was new for him, but he took it in stride.
“There was a level of anxiety, which is healthy, right?” he said. “That kind of raises your attention to a thing that might go wrong.”
While most drivers might have eased off the gas heading into it, Korbmacher did the opposite.
“I even caught another gear right there,” he said, gesturing back to the stretch of highway above the arrestor. “Then right before the sign there, I just dropped it in neutral and pointed down the middle.”
Following the test a front-end loader worked to pull the truck from the nets, and WYDOT staff started cutting the steel tapes so the canisters could be removed and replaced. Brackin, the designing engineer, said the arrestor would be back up and running by 5 p.m. that day, a roughly six-hour turnaround.
Any net that a car touches is removed, but WYDOT staff have a full replacement set at their shop in Jackson. Insurance companies generally cover the cost, Hammond said, which runs around $13,000 per net, plus staff time.
“Insurance companies see that as a viable expense or a reasonable expense,” he said. “Compare that to the cost of someone’s life, it’s pretty inexpensive.”
Now that the redesigned arrestor has proved its mettle, WYDOT officials plan to use the concept elsewhere. The first arrestor in Wyoming was on Highway 16 outside Buffalo, but that has a setup like the original design on Teton Pass.
A recent crash into the arrestor yielded similar results to the log truck in 2019.
“It got used actually last week,” Hammond said Thursday, “successfully in the way that no one died and the driver and passenger were fine, but unsuccessful in that the vehicle did go through it.”
That one will have a similar redesign, he said, maybe not exactly the same as the Teton Pass structure, but close. WYDOT also still plans to build a second arrestor closer to Wilson on the final straightaway before the speed limit drops to 25 mph.
Hammond didn’t give a deadline for constructing the second arrestor, which will require WYDOT to carve out a second eastbound lane on Highway 22 above Wilson. Addressing traffic problems on the highway and completing the rebuild of the Snake River Bridge are slated first.
“We’re looking at making sure that moves forward, so we can eliminate some of the concerns that people had about traffic backups,” Hammond said.
No matter how far in the future those projects are, the people involved are happy to see that the new design was successful.
“We’ve got to have confidence in the system,” Reiner said.
Brackin, the engineer, agreed.
“We really want to be able to test it and know that it works,” he said. “We have people’s lives in our hands.”