Continuous flow lanes proposed as fix for Oak Hill ‘Y’ congestion

Proposed fixes around the so-called “Y” intersection in Oak Hill should put off long-term decisions to fix the congestion magnet for at least seven years.

 

Engineer Keith Taylor presented the two-phase project at the CAMPO Transportation Policy Board meeting last night. The bottom line was that improvements to the five nearby intersections, and the actual split of US 290 and SH 71 known as the “Y” could provide significant traffic relief.

 

“I want to thank TxDOT, the city and Travis County for thinking outside the box,” said former Sunset Valley Mayor Jeff Mills, who represents Travis County on the board. “I think a 30 to 40 percent improvement in traffic flow for $8 million is a fantastic result. I just want to applaud you for doing this. I can’t wait to see it.”

 

Improvements to half the intersections – at Joe Tanner, William Cannon and the “Y” itself – will use continuous flow lanes. Such lanes take turning cars out of the way of oncoming traffic so both directions can continue to turn at the same time. To see how traffic flows, you can go to watch a model on YouTube at http://www.youtube.com/watch?v=soRw9vqaM-k.

 

“It does the job of reducing the number of phasings of the signals, as well as recapturing the time lost between signals, as people step on their brakes,” Taylor said. “Not only is it increasing the time on lights and decreasing signals, the combination is now matched up with through movements, so that both are not happening at the same location at the same time.”

 

The improvements will be the second phase of the improvement project, a partnership among Austin, Travis County and TxDOT that will cost $5.2 million. Austin will pick up $2.8 million of the cost, with Travis County footing $1.5 million of the bill and TxDOT paying $900,000 towards the intersections. Bids will go out next spring, with construction completed in spring 2014.

 

Those changes, even with minimal disturbance to the right-of-way, are not without cost to surrounding facilities. Due to the improvements, Capital Metro will be forced to move its Park and Ride location from the southeast corner of William Cannon.

 

“We have one possible location on this map, but Cap Metro has a number of other potential locations they’re considering for their service,” Taylor said. “One of the things that we’ve been working with them on is orienting our construction so that they can remain at that location for as long as possible.”

 

Improvements at three other intersections – FM 1826, Convict Hill and the driveway of the ACC-Pinnacle campus – will consist of dual turn lanes and a center lane that will improve safety and traffic flow, Taylor said. Shoulders along these intersections will be widened for cyclists and pedestrian crossings will be upgraded.

 

That aspect of the improvements, the project’s first phase, will go out for bid in July with construction anticipated to take approximately nine months. Of the $2.8 million budget, TxDOT will pick up $1.8 million and Austin $1 million, with the understanding that Austin will control and phase all signals in the area.

 

These improvements should see the region through the next 7 to 10 years of growth, giving local leaders more time to come up with a permanent fix, Taylor said. Much of the discussion of how to improve the “Y” has been stymied in recent years, caught between the projected growth and the concerns of environmentalists.

 

The continuous flow lanes around the “Y” will be a first in Texas. Taylor said modeling has shown that the configuration can improve traffic flow between 40 and 50 percent at outlying intersections and probably 30 to 40 percent at the “Y.”

 

“You’re going to get a much better performance overall,” promised Taylor, who had traveled to Utah with Austin traffic engineers to view the intersections and how they worked in Salt Lake City, where they were first introduced.

 

The intersections should have better safety implications, too, cutting down on crashes that typically happen at congested intersections, Taylor said. Taylor said he witnessed few problems with vehicle movement in Salt Lake City.

 

Austin has considered using continuous flow lanes at a number of the city’s more problematic intersections. Williamson County has considered the new configuration for its intersection at FM 1431 and Ronald Reagan Parkway.