Alaska, Featured, Technology

Keeping Thompson Pass Clear

by Allison Sayer for Seward City News-
Plow truck at the Thompson Pass DOT Station. Photo by Allison Sayer.

What’s it like to drive a plow truck in one of the snowiest places on earth? And what kind of equipment can move all that snow? I visited the DOT station in Thompson Pass on December 21 to learn more about this tough job. Foreman Mark Hanson was kind enough to show me their equipment up at the shop.

It turns out the actual snow plows are a standard size. However, they are mounted on much more powerful trucks than a typical plow would be. The Alaska DOT uses triple-axle Mack trucks to push their plows. Unlike most snow removal vehicles, these trucks are all wheel drive. The driver can also manually control how much power each of the two rear axles receives, if need be.

The entire truck is lifted high off the ground to accommodate the transfer case that powers the front axle. An average person must reach high for the handle located at the very bottom of the cab door.

Next year, these work horses will be retired. They will be replaced with similar trucks that are newer and have more horsepower.

On the inside, the truck looks fairly standard, with the exception of a small monitor mounted on the dashboard to the right of the driver. This monitor is one of the key components of the system that helps drivers stay on the road during the total whiteouts that are frequent in the pass.

The trucks are mounted with two Trimble GPS receivers. There is also a GPS base station located in Thompson Pass. The truck’s exact position can be mapped to within two inches through constant comparison between its location and the fixed station. The highway was accurately mapped by engineers who drove back and forth with mapping devices on their cars. All of this information is combined to produce a simple image on the monitor that shows a plow truck’s position on the highway.

Even the most skilled driver can not see the lines on the road during a true white out. The software alerts drivers if the truck is not centered in its lane. If the truck passes over the centerline, the centerline turns red on the display. The same happens if the truck passes over the white line on the shoulder.

An optional feature vibrates the seat to the left and right of the driver as well. This feature can be turned off for performing tasks like shoulder work, which require driving over one of the lines.

Plows are equipped with radar that can help them to “see” cars that are buried in snow banks. These show up as rectangles on the monitors inside the cabs.

The monitors within the trucks also show mile markers and signs that help the plow drivers to confirm their location on the highway. During a true whiteout, the drivers are not able to see mile markers along the sides of the road.

Monitors within Thompson Pass plow trucks display the truck’s precise location on the road. Photo by Allison Sayer.

The evolution of the Alaska DOT GPS technology is a typical Alaskan story. Scientists from the Lower 48 came up to install the system as a prototype over ten years ago. The “Smartplow” system has since been privatized and sold to other communities. Meanwhile, Alaskan users performed some after market modifications to make it practical.

The original system projected an image from the rear of the cab to the front. Because the image was projected, the original image was reversed. However, this system had a serious drawback. Drivers banged their heads against the projector when the road was bumpy, and if there had been an accident a driver could have been injured.

Ordinary monitors could not replace the old projectors because the system produced a reverse image. However, DOT staff realized that teleprompters also worked in reverse. Last year, the old projectors and screens were removed and replaced with small teleprompter screens. These screens worked like a charm, and were much safer for the cab of the truck. 


After viewing a few more components of the plow truck, including the sand and brine tanks, I had a chance to get into the truck with driver Tavis Chaffin.

The first thing Chaffin did when he got into the truck was make sure that the seat, steering wheel, and other points were adjusted exactly the same as they always were when he was the driver. Keeping the cab consistent is essential to creating reference points based on looking at the hood of the truck itself. This helps drivers to gauge where the large belly blade located beneath the truck is, and how far away it is from the guardrail.

It was time to do some shoulder work. If the snow on the sides of the road gets built up too high, snow can’t be moved off the road effectively. This work needs to be done during storms as well. On this beautiful day, Chaffin had time to methodically work on the shoulders. This involved using the belly blade located underneath the plow and its extendable wing to throw snow farther away from the highway.

It seemed like there was some finesse involved in perfecting the angle of the blade and the wing. However, both Chaffin and Hanson downplayed this.

With sun shining down on the pass, and visibility as far as the eye could see, this was a somewhat casual day. Chaffin told me that routine maintenance that takes up “about 40%” of a plow driver’s time. According to Chaffin, the other 40% is “good, honest work,” with the remaining 20% left for “sheer terror.”

During a big storm, it doesn’t take long for 8 to 10 inches of snow to pile up on the road. This can occur even with two plow drivers making continuous passes. The wind can pile up a 3’ drift on the road in less than half an hour. Combined with near zero visibility, this can create virtually impossible driving conditions for ordinary cars. When the avalanche danger is severe, or if the plows can’t keep up, the road closes. However, closing the road is a last resort.

The big storms are Chaffin’s favorite part of the job. It makes him feel good when cars decide they can not continue and pull over to wait for him. “You’re getting people over the pass,” he says.

Chaffin also feels gratified that he can assist drivers that have lost control and become stuck on the highway. The plow is often the first responder. In addition to the radar that helps them find cars, plows are equipped with emergency response equipment including fire blankets, tow straps, and first aid kits. Plow drivers relay information via VHF that goes through permanent repeaters to police, fire fighters, and emergency medics in town. Drivers are trained in first aid and CPR.

During truly big storms, the road is closed altogether. Sometimes the snow is so deep, the belly blade would simply stop the truck in the snow like a brake. Trucks can use just the front plow. Tavis recalls jumping out of the truck to manually empty the front plow with a shovel during a recent storm. “I was waist deep on the centerline [of the highway],” he said, “That’s when it gets fun.”

Avalanche danger, however, is not fun. When there is major danger of natural avalanches, the highway is closed. However, drivers are still exposed. All drivers wear beacons, and communicate their positions constantly to other drivers using VHF radios. Schoolbus, one of the peaks just above the official Thompson Pass sign, is notorious for burying the road. Thompson Pass staff are trained to trigger avalanches with ammunition, if necessary. This becomes part of the job to protect the highway from surprise avalanches.

Foreman Mark Hanson (R) and driver Tavis Chaffin (L) at the Thompson Pass DOT shop. Photo by Allison Sayer.

Plow technology has come a long way since the early days when Thompson Pass was plowed with bulldozers. Clearing the pass took so long drivers would sometimes nap underneath the warm engines, and the Thompson Pass DOT station employed a full time cook. However, it is still an extremely difficult job. During a big storm, drivers drive continuously for twelve hours. “I learned to pack a lunch,” says Chaffin, “You go as fast as you can to keep up.”

I wondered whether twelve hours of driving took a toll on drivers’ bodies. “I’m white knuckled the whole time,” says Chaffin, “after a big storm, I’m sore.”

So what can we ordinary drivers do to make the plow drivers’ jobs easier? Foreman Mark Hanson asked me to remind drivers to keep their headlights on. It is the law in many parts of Alaska, although the law is not often enforced. More importantly, the drivers will see you sooner, which makes their job a little easier.

Last year, my neighborhood made an effort to bring our local DOT some cookies or treats every once in awhile. We have not rekindled this tradition yet, but it’s not a bad idea to get that going again. After all, their work helps all of us to go about our business safely through the rough Alaskan winter.


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