by BRAD ROLLINS
The project, which has been in the works since January 2010, would widen about 4,000 feet of Hunter Road between Bishop Street and Wonder World Drive, to three- and five-lane segments with bicycle traffic accommodated either on sidewalks or bike lanes. It also includes a bridge over Purgatory Creek where flooding periodically closes the existing low-water crossing.
But widening the road alone won’t relieve all congestion on that stretch of road, traffic engineers told council members during a regular meeting earlier this month. That’s because the irregular intersections with San Antonio and Dixon streets will continue to snarl traffic and pose a safety hazard unless they are addressed, they said.
“Corridor capacity is not defined purely by the number of lanes. It’s defined by the efficacy of the intersections. Although a roadway has the capacity of up to 1,900 vehicles per hour per lane, it is the intersections, those valves that control how much traffic can go through,” said Gary Schatz, an Austin civil engineering assistant director who gave council members a crash course on the use of roundabouts. “It’s like going to Home Depot and buying a pipe this-big but only buying a valve this-big to go on it.”
San Antonio Street intersects Hunter at a 60 degree angle, Kimley Horn engineer Brian Becker said, which makes some turns difficult and ensures northbound traffic on Hunter does not slow down as it zips onto San Antonio. In addition, Hunter’s intersection with Dixon street less than 150 feet away from San Antonio creates conflict during peak hours as cars try to turn into, or out from, surrounding residential areas.
Becker proposed instead rerouting Dixon Street through currently vacant lots to intersect Hunter more or less squarely across from San Antonio. Instead of a stop sign, traffic light or nothing at all, Becker recommended construction of a 105-foot diameter roundabout to move cars through the junction and signal the start of the Hopkins and San Antonio streets historical districts.
“A roundabout is a perfect use for intersections with irregular geometry, which is the situation that you see here… It’s a great traffic calming device. It just lets people know that you’re leaving from an auto-centric area south of this intersection into a more people-centric area as you get into the historic district[s],” Becker said.
San Marcos planners have embraced roundabouts lately, building two on Cheatham Street in the Rio Vista Terrace and proposing them elsewhere, including at North LBJ Drive at Holland Street and at Stagecoach Trail and Snyder Hill Drive at the entrance to the Willow Creek neighborhood.
Roundabouts reduce the risk of total auto crashes by 40 percent, of crashes causing injury by about 70 percent and of fatal crashes by about 90 percent over intersections with traffic lights, according to an Insurance Institute of Highway Safety study, Schatz said.
“I’m telling you folks that I have no other tool in the toolbox that is that good,” Schatz said.
Council member Wayne Becak, wary of the expanding pricetag on the project, wondered if the re-routed street and roundabout might be overkill. He suggested that the planned center turn lane on Hopkins would ease traffic flow through the intersections.
“I don’t understand why we’re going to close a perfectly good street, buy right-of-way and build another street. Now that we’re going to have a center turn lane I don’t see any problem with the amount of traffic that’s on Hunter. I drive that several times a day. The problem is that there aren’t any turn lanes… Seems like a turn lane is going to solve that,” Becak said.
A majority of his colleagues, however, said they like the roundabout idea and instructed city staff to include it in the project design.
The Hunter Road widening was anticipated to cost $6.9 million when it was authorized by the city council in January 2010. At the time, council member Ryan Thomason argued on behalf of a less-expensive plan that would have saved $1.8 million by using a low-water crossing engineered for a 25-year flood instead of a full-fledged bridge over Purgatory Creek.
The council at the time opted for the more expensive package, in part, because they wanted bicycle and pedestrian traffic to be able to pass underneath the bridge as a connection between the Purgatory Creek Natural Area trail system and the rest of the city.
Under questioning from council members John Thomaides and Kim Porterfield, however, Becker said the creek channel would need to be dredged to allow enough clearance for walkers and bikers to pass underneath, adding complexity and cost to the project. Said Porterfield, “That was not the direction the council gave.”
City Manager Jim Nuse and engineer Linda Huff said they would find a way to make the pedestrian connection.
The Hunter road project is being paid for with $6 million in state Proposition 12 funds appropriated by the Capital Area Metropolitan Planning Organization in addition to $4.2 million saved when the Wonder World Drive extension project came in under budget. Construction is expected to start in August 2013 and last about a year.Email | Print