Austin will lower speed limits on dozens more streets as part of a continuing attempt to reduce traffic deaths and serious injuries. The City Council approved the measure Thursday as Austin's traffic fatalities were on track to exceed last year's record-breaking death toll.
Traffic experts warn changing speed limit signs without adjusting the design of roads has limited advantages, although the stricter rules tend to tame the most egregious speeders.
But in some instances, widening the gap between the legal limit and how fast people feel comfortable driving on a road could introduce new dangers by increasing the difference in travel speeds, researchers said.
Austin's latest speed limit project started in 2020 on streets within a perimeter bounded by U.S. 183, Ben White Boulevard and MoPac — an area defined by city officials as the "urban core."
With Thursday's council vote, the effort is now shifting to streets outside Central Austin. Speeds will be lowered along 48 major thoroughfares, including parts of Kramer Lane, Far West Boulevard, Stassney Lane and Burleson Road.
Four out of five streets affected would have their speed limits reduced by 5 miles per hour. The rest would go down by 10 miles an hour except for part of McKinney Falls Parkway. That segment between Burleson Road and U.S. 183. would be lowered from 55 mph to 40.
"Speeding is one of the primary contributing factors to serious injuries and fatalities," Austin Transportation Department managing engineer Eric Bollich said. "A small difference in lowering speeds can have a big impact in outcomes when crashes do happen, hopefully they're less serious and not fatal."
ATD considered several factors when deciding where to lower speeds, including average daily traffic, the number of driveways along a stretch of road, how many pedestrians and cyclists use the street, and the rate of crashes and injuries.
City engineers also used a Federal Highway Administration tool called USLIMITS2 that recommends limits closer to the median speed drivers are already traveling.
But traffic experts say telling people to slow down on roads designed for faster speeds can create a dangerous differential in which some people obey the reduced speed limit and others drive at the speed for which the road was originally designed.
"You increase the variance at the speeds at which people are traveling, because you have the scrupulous rule-followers sharing the road with the people who are taking their cues from the design speed," said Daniel Herriges with Strong Towns, a Minnesota-based nonprofit focused on city development.
"If the city's really serious about affecting a major change in driver behavior, there needs to be physical changes to the design of the roadway," he said. "The speed limit that people actually drive is influenced much more by the design speed of the road than it is by the posted speed limit, particularly in the absence of really visible enforcement."
Speed limit enforcement in Austin has plunged in recent years as more traffic cops have been reassigned to patrol duties like responding to 911 calls. The number of speeding citations issued in the last five years fell by 90% as traffic deaths soared.
Austin's City Council also approved a measure telling the city manager to find ways to increase traffic enforcement on freeways, frontage roads and busy streets where most severe car crashes happen. The resolution requires an update by July 15, before major decisions are made on the next annual budget.
ATD says lowering speed limits is just one tactic to change driver behavior. The City of Austin is spending hundreds of millions of dollars in voter-approved bond money on improving busy traffic corridors by fixing intersections, upgrading bicycle and pedestrian infrastructure, adding pedestrian hybrid beacons and installing other safety improvements.
Even on unchanged roads, reduced speed limits can help slow the most aggressive drivers, according to the Insurance Institute for Highway Safety.
In 2018, the IIHS examined Boston's move to lower speed limits from 30 mph to 25 citywide. The number of drivers exceeding the speed limit by 10 miles per hour decreased by 29.3%.
"It's really the top end of the distribution that you want to address," IIHS president David Harkey said. "You can start to rein in the more aggressive speeders."
The City of Austin is hoping for similar results.
"If speed limits are lowed a little bit, I think it's human nature not to be exceeding a speed limit by 15, 20 miles an hour," Bollich said. "Some people will, but for the most part, I think that has the highest impact on those who are going above the speed limit the most."
