CHEYENNE — Who knew drivers help determine the variable speed limit for segments of Interstate 80?

Drivers’ speeds are tracked by sensors embedded in the pavement and installed on markers alongside the highway.

However, that’s just one element the Wyoming Department of Transportation uses to calculate and set variable speed limits.

Other factors include weather, road condition and recommendations from Wyoming Highway Patrol troopers and department maintenance operators.

This is high-tech stuff.

“That’s kind of the general algorithm we use,” said Vince Garcia, manager of Geographic Information Systems and Intelligent Transportation Systems.

“A lot of engineering is behind it.”

The decisions to drop speed limits are made in the department’s transportation management system nerve center, which is located in the basement of the former Quest office building in north Cheyenne.

This is where operators originate road and condition messages that appear on the electronic signs, such as warnings of slick roads, blowing snow or both.

Some of the older signs will have to be replaced if the Wyoming Legislature passes a bill to allow the department to set an 80 mph speed limit on designated segments of the interstate system.

The aging signs are fixed and can’t register speeds faster than the current 75 mph.

The newer LED signs will work fine, officials say.

Meanwhile, back at the nerve center, Garcia said the first source of road and weather information is a patrolman or maintenance person who is at the scene.

In the absence of visual inspection, the staff will use other information systems, road and wind sensors and the WYDOT web cams, which monitor road conditions and visibility.

If there are surface or visibility problems, the center’s supervisors slow down the traffic.

Garcia said the driving conditions are safer when everyone travels at the same rate of speed.

If some drivers are traveling 55 mph and others 80, the goal is to pull the outliers into a middle speed, or a pace speed.

In addition to the supervisors in the center, highway patrol troopers and department maintenance people can direct changes in the speed limit, Garcia said.

Winter storm

The center was particularly busy one morning last week.

On one wall were computer screens that displayed the variable speed limits on segments across I-80 along with the web cam images of highway conditions.

Because of blowing snow and slick roads, the speed limit on I-80 in the Arlington area west of Laramie was set at 45 mph.

Gabe Gutierrez had six screens on his desk. One displayed a map that told him where every snow plow operator was located.

With a click, he could find out how fast a plow was moving and who was operating it.

The snow plow operators kept calling in with information. Everybody used a code. The 8392 code means slick roads and snowfall.

Gutierrez used the information to update highway advisories on the WYDOT website, radio and 511 reports.

On that day, the snow chain law was in effect for South Pass.

Gutierrez could drop the chain law with one click.

Next door to the center, behind a glass partition, is the Wyoming Highway Patrol dispatch.

The dispatchers and transportation management center exchange information about highway accidents.

The center also has a meteorologist who provides forecasts for highway maintenance staff and truckers.

Truckers, Garcia said, like the variable speed limit and warning signs.

The center runs 24 hours a day, as does the traffic.

“It takes a skilled person to manage the traffic,” Garcia said.

Contact capital bureau reporter Joan Barron at 307-632-1244 or joan.barron@trib.com

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