Posted: 12:00 a.m. Sunday, February 19, 2017
The reduction from five to three lanes, with better bike lanes, came up in a study of the U.S. 183 corridor.
Just to calm the waters up around the Arboretum, if I can, know first that the city of Austin is not about to narrow Jollyville Road from its current five lanes to three lanes. At least not in the next few years.
City transportation officials told me this last week, and I believe them. So Northwest Austin residents who have been atwitter about the possibility after it emerged as an option in an ongoing study of improvements in the U.S. 183 corridor for active transportation (cycling and walking, basically) can probably relax for now.
But the prospect of Austin officials putting the key thoroughfare on a road diet, something the city has already done to about 45 other road segments in Austin, provides a timely excuse to kick it around here. No doubt youve noticed the changes around town over the past 15 years or so, primarily the conversion of four-lane city streets to three lanes (a travel lane in each direction and a center left-turn lane), with wide bike lanes.
The city maintains, with what seems to be credible backing from studies and national transportation regulators, that for roads with traffic loads under 20,000 vehicles a day, cutting out a through lane in each direction can actually make things better for drivers. And, of course, for bicyclists, who typically would go from having no bike lane, or slender ones delineated only by painted stripes, to having a wide lane in each direction possibly protected by curbs or pylons.
The theory, as laid out in a May 2015 city report on right-sizing streets, is that the real traffic choke points on most four-lane streets are the intersections, not the stretches in between. That report says that at an intersection with a traffic signal, just 600 vehicles an hour can make it through the intersection on each lane. So if there are two lanes at the intersection (and those intersection lanes are typically retained in road diets), thats 1,200 cars an hour.
But the through lanes, the city argues, can each carry 1,800 cars per hour. So one lane, under this line of reasoning, is roomy enough to handle 50 percent more vehicles than can actually make it through the intersection.
On the upside (leaving the cyclists out of the argument for the moment), having a center turn lane or a median with left-turn bays means that oncoming cars have a 10- to 12-foot buffer zone. If a car strays out of its lane, it would be less likely to collide with an oncoming car. And there are fewer rear-end collisions as well, the argument goes, because people in a four-lane configuration might come up on a left-turning car unexpectedly and be unable to stop in time.
Nationwide right-sizing studies, that 2015 report says, typically observe between 19 percent and 47 percent reductions in overall crashes.
Oddly wide range, but, OK.
Back to Jollyville, which the careful reader might have noted above is a five-lane street, not a four-lane one. That means it already has the vehicle safety benefits associated with a center turn lane. So the question, to the extent that at some point the city will be mulling it for real, is whether the loss of a vehicle lane in each direction is worth the added safety for cyclists.
I asked city officials whether the city had actually done any five-lane to three-lane road diets in Austin. I was surprised to hear that it has occurred eight times: on Shoal Creek Boulevard north of Steck Avenue, Harris Ridge Boulevard near Parmer Lane, Grove Boulevard north of Riverside Drive, Mesa Drive north of Spicewood Springs Road, Rutherford Lane near Cameron Road, Northcross Drive west of Burnet Road, Middle Fiskville Road north of Koenig Lane and East 51st Street west of U.S. 183.
However, all of those road sections have traffic volumes less than the section of Jollyville under study, according to Nathan Wilkes, an engineer with the Austin Transportation Department.
Jollyville Road at two spots between Great Hills Drive on the south and Spicewood Springs Road on the north had 18,000 to 19,000 vehicles a day in counts taken last year, Wilkes said. That means it is bumping up against that recommended limit for road diets.
What about bicycles, I asked Miller Nuttle, the campaigns director for BikeAustin, which supports road diets? He didnt have a count.
So I went out Wednesday morning to Jollyvilles intersection with Braker Lane to get a look at both the car and bike volumes during rush hour. I stayed for 90 minutes, starting about 7 a.m. It was a sunny day with temperatures in the low 40s, admittedly chilly for biking but about normal for mid-February.
My best estimate of vehicle volumes, based on counting cars going southbound during the 80-second green light cycles? About 1,500 per hour in that most prominent morning direction. The flow of cars was sporadically thick and pretty speedy. But I never really saw any congestion. No car had to wait through more than a single cycle of the light at Braker.
As for bicycles, well, I saw just 10 in those 90 minutes, and only four going southbound. For a 45-minute period starting at 7:32 a.m., not a single bicycle went by in either direction. Those four southbounders would amount to 0.3 of 1 percent of the total volume of cars and bikes.
Consider how much of the 60-foot-wide, curb-to-curb road would go to bikes 40 percent under a reduction to three car lanes, and the disparity is pretty stark.
Nuttle, perhaps anticipating that very few cyclists currently brave Jollyvilles unseparated bike lanes, said it is a chicken-and-egg situation. People wont ride bikes in significant numbers, he said, until Austin has a connected network of all ages and abilities bike lanes wide and/or protected pathways, or off-street trails but the lack of bike volume is used as damning evidence to argue against spending the money (and allocating asphalt) to build those better bikeways.
Maybe so. Its a theory. Austin has done a lot to help cyclists over the past 10 years or so, and, while there has been some added usage, bike commuting has yet to mushroom. Were still looking at less than 1.5 percent overall, based on the U.S. Census Bureaus 2013 American Community Survey, with something like 10 percent in the core of the city, according to bike advocates here. And Jollyville is far away from that core.
The study was occasioned by the coming expansion of U.S. 183 with four toll lanes, and two added free lanes, between MoPac Boulevard (Loop 1) and RM 620. Officials decided it would be too dangerous to put an off-street bike path along U.S. 183 because of all the business driveways through there and decided to look at nearby thoroughfares such as Jollyville.
The early version shows that five lanes could be maintained, with off-street bike lanes, for $42 million. The three-lane version is cheaper: $15 million.
City officials said nothing will happen until the U.S. 183 expansion is done, perhaps five years from now.
Maybe with all that added capacity nearby taking some of Jollyvilles current traffic, they said, the street could thrive in a slimmed down version. But thats a fight for another time.
Follow this link:
Could Jollyville Road drivers survive a 'road diet'? - MyStatesman.com
