State Highway 161 drivers who once sat log-jammed at a frustrating chokepoint in Irving started sailing through a three-mile stretch of highway immediately after the Texas Department of Transportation opened up inside shoulders to rush-hour motorists.

According to data released Thursday, traffic speeds on the freeway between State Highways 183 and 114 more than doubled after TxDOT started letting drivers use the shoulders during rush hour. Officials say it’s the first place in Texas where drivers are allowed to use shoulders — though they’re now exploring other places to do the same thing.

That Irving stretch of SH 161 is often called “three-mile island” because TxDOT owns and operates it, while the North Texas Tollway Authority owns and operates the rest of the highway. TxDOT’s portion is only two lanes, while NTTA’s portions are three lanes. That lane imbalance effectively acted as a funnel that backed up traffic each day.

“This has been a huge problem for the North Texas Tollway Authority,” regional transportation director Michael Morris said Thursday. 

TxDOT opened shoulders starting Sept. 14. Experts say one of the best ways to solve urban congestion is to focus on redesigning or rebuilding specific chokepoints. Simply relying on expanding highways, they say, can actually make traffic worse.

State Highway 161′s average morning rush-hour speed for the eight work days before the shoulders opened was 30.7 mph. The average northbound speed in the eight work days after the opening shot up to 66 mph.

The average evening rush hour speed for the same time period was 23.3 mph. The average southbound speed jumped to 62 mph after the opening.

Morning motorists who drove the stretch at 8 a.m. saw the biggest difference. That’s when average speeds increase 57 mph. Evening commuters who drove it at 4:30 p.m saw average speeds increase 51.2 mph.

Morris said the North Central Texas Council of Governments will keep an eye on the area to make sure congestion doesn’t return.

“We’ll continue to monitor that,” Morris said.

TxDOT, meanwhile, is looking at applying the same concept to other North Texas corridors.

“Due to the success, it’s something we’re going to look at in the future for sure,” said TxDOT spokesman Tony Hartzel.

At the top of their list is Central Expressway north of LBJ Freeway. It could take years to get federal approval and convert carpool lanes back to shoulders that would then be opened up during rush hour. But a discussion has already begun.

“It’s a candidate,” Hartzel said.

Presented by The Dallas Morning News

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