Speed Management in Austin
Speed Management in Austin
Vision Zero Analytics
SPEED MANAGEMENT IN AUSTIN
Assessing the Safety Performance of Traffic Calming and Speed Limit Reductions
2026
Summary
Speed management is a core strategy of Austin Transportation and Public Works’ (TPW) efforts to eliminate traffic fatalities and serious injuries. Examining three related strategies—arterial speed limit reductions, traffic calming treatments, and citywide residential speed limit reductions—Austin has found overall decreases in motor vehicle speeds and crashes where the City has focused its speed management interventions. These improvements translate to reductions between 0.04 mph and 5.9 mph for the 85th percentile speed of vehicles, depending on the data source and countermeasure.
Speed data show that the number of vehicles traveling 10+ mph over the speed limit at treatment locations dropped between 8% and 78%, depending on the context. These speed management interventions are associated with annual fatal and severe injury crash reductions of between 17% and 39%. In total, yearly comprehensive crash costs have fallen along these roads by as much as $160.4 million. TPW will continue to employ speed management strategies throughout the city and utilize multiple data sources to corroborate findings.
Problem Statement and Solutions
Speeding is a leading contributing factor in severe traffic crashes nationwide. In 2023, the National Highway Traffic Safety Administration reported that speed was a factor in 29% of U.S. traffic fatalities, claiming over 11,000 lives. The risk posed by speed is not linear: as velocity increases, a driver’s field of vision narrows, braking distances increase and the impact force of collisions rises. This effect is most lethal for vulnerable road users like people walking or biking. According to the AAA Foundation for Traffic Safety, the risk of a vehicle killing a pedestrian climbs from 10% at 23 mph to 50% at 42 mph.
Solutions: Austin’s Holistic Speed Management Approach
In 2020, TPW launched a Vision Zero-led initiative to develop a holistic speed management strategy rooted in Safe System principles. Following a multidisciplinary workshop with the Vision Zero Network and Institute of Transportation Engineers, the City moved from a reactive approach to a more proactive, data-informed speed management strategy that includes the following aspects:
- Policy Alignment: Formalized “Target Speeds” within the Transportation Criteria Manual to ensure that street design dictates driver behavior.
- Data-Informed Traffic Calming: Developed a new traffic-calming methodology that pivoted from a request-based program to one that identifies which residential streets to prioritize with interventions based on crash history, vehicle speeds, street geometry, equity and other contextual factors.
- Speed Limit Reductions: Systematically reduced speed limits by 5–15 mph on certain Level 3 Austin Strategic Mobility Plan (ASMP) arterials when appropriate; lowered the default limit to 25 mph across approximately 800 miles of residential streets—generally those 36 feet wide or narrower—and most of the downtown grid.
Based on recommendations from TPW traffic engineers, Austin City Council authorized lower speed limits along 73 segments of high-speed arterial roadways in 2020 and 2022. Beginning with arterials in Austin’s urban core and later expanding to roads outside the urban core, these changes lowered speed limits between 5 and 15 mph on approximately 100 miles of roadways.
In recommending speed limit changes, TPW staff relied on USLIMITS2, a Federal Highway Administration-endorsed, data-driven tool that recommends speed limits by analyzing real-world driving behaviors, crash risks and roadway context. Compared with traditional methods that rely mostly on how fast drivers are already going, this approach better aligns with Safe System thinking by incorporating safety perspectives and surrounding conditions.
This paper evaluates the efficacy of these systematic changes in reducing vehicle speeds, as well as the frequency and severity of related crashes in Austin.
Methodology
Staff compared before-and-after speed data from various point locations along each study corridor to measure the safety impact of of traffic calming treatments and speed limit reductions. This analysis focused on several key metrics:
- 50th Percentile (Median) Speed: The speed at which half of all drivers travel at or below.
- 85th Percentile Speed: A standard engineering benchmark representing the speed at which most drivers travel at or below.
- Egregious Speeding: A measure of “high-risk” drivers traveling 10 mph or more over the speed limit.
For speed limit reductions, staff supplemented direct measurements with metrics from StreetLight Data, a platform that aggregates anonymized, real-time information from connected vehicles. By comparing pre-intervention data from 2019 with post-intervention data from 2024, staff were able to analyze speed and volume trends across more locations.
Finally, staff looked at crash and injury rates before and after the implementation of traffic calming treatments and speed limit reductions to correlate interventions with actual safety outcomes.
Results
Arterial Speed Limit Reductions
Speeds
TPW collected 24-hour speed data at 186 unidirectional points along the treatment arterials before and after speed limits were changed.
On treatment arterials, speed data showed an average 1.5 mph reduction in 50th percentile speeds and an average 1.7 mph reduction in 85th percentile speeds. StreetLight data for these same locations showed more modest decreases of 1.1 mph and 0.6 mph for 50th and 85th percentile speeds, respectively. In comparison, StreetLight data for all Level 3 arterials across the city showed even smaller reductions—just 0.4 mph for 50th percentile speeds and 0.01 mph for 85th percentile speeds—indicating that the targeted speed limit changes had a positive impact relative to general traffic trends.
To further assess safety impacts, TPW examined egregious speeding. The point speed data showed 3,567 fewer instances of vehicles traveling at least 10 mph over the speed limit after new signs were installed, an 8% reduction. Overall, 51% of locations recorded fewer vehicles engaged in egregious speeding and 53% of data points showed a reduction in the proportion of vehicles exceeding the speed limit by 10 mph or more. Aggregating measurements from all sites, there was a 14% drop in the rate of vehicles traveling 10 mph or more over the speed limit, from 2.9 vehicles per 100 before new speed limits to 2.5 vehicles per 100 after.
Arterial Speed Limit Reductions
50th Percentile Speed Reductions
85th Percentile Speed Reductions
Crashes
Approximately 70% of treatment arterial segments experienced lower annual comprehensive crash costs after speed limit reductions, resulting in an overall decrease of 23%, or $106.2 million per year. These corridors also averaged up to 76.0 fewer injury crashes and 8.9 fewer fatal and serious injury crashes per year—improvements of 23% and 17%, respectively.
Crash Reductions for Arterial Speed Limit Changes Compared to All Level 3 Streets
Fatal and Serious
Injury Crashes
All Injury Crashes
All Crashes
Comprehensive Crash Costs
As shown in the graphic here, these results slightly but consistently outperformed citywide trends on Level 3 streets over the last 10 years when comparing 2016–2020 and 2021–2025. Treatment arterials saw larger reductions in fatal and serious injury crashes, all injury crashes, total crashes and comprehensive crash costs.
Traffic Calming
TPW’s traffic calming efforts use various materials to slow vehicular traffic, including traffic circles or mini-roundabouts, medians or pedestrian islands, curb extensions, chicanes, speed humps, speed cushions, raised crosswalks and Dynamic Speed Display Devices. Most traffic calming projects are on Level 2 streets, but speed cushions and other countermeasures may be implemented on a variety of street levels, including residential streets.
Most of the traffic calming projects analyzed in this paper were sponsored and implemented by TPW’s Speed Management Program after 2022. Vision Zero has also included nine older traffic calming projects completed by different programs to increase its analytical sample size.
Speeds
Staff analyzed before-and-after speed data from 25 traffic calming projects completed after 2020. Both point speed data (48 locations) and StreetLight data (16 street segments) showed average reductions in 50th and 85th percentile speeds, with the point data indicating larger decreases: 5.6 mph for the 50th percentile and 5.9 mph for the 85th percentile. StreetLight data showed a 4.4 mph reduction for the 50th percentile and a 3.4 mph reduction for the 85th percentile.
By comparison, all Level 2 streets citywide—using StreetLight data as a proxy comparison group—experienced little change between 2019 and 2024: 50th percentile speeds decreased by just 0.2 mph, while 85th percentile speeds increased by 0.4 mph. Across both datasets, traffic calming consistently reduced vehicle speeds beyond broader citywide trends.
Point speed data showed 5,300 fewer vehicles traveling at least 10 mph over the speed limit on the 25 treatment streets—a 78% reduction. Overall, 79% of locations recorded fewer vehicles engaged in egregious speeding, and 87% saw a lower proportion of vehicles exceeding the speed limit by 10 mph or more. Aggregating all measurements, the rate of excessive speeding fell 72%, from 6.4 vehicles per 100 to 1.8 vehicles per 100.
Of the 25 projects, 15 used speed cushions and 10 used other traffic calming measures, such as pedestrian crossing islands. Projects with speed cushions reduced vehicles traveling at least 10 mph over the speed limit by 89%, compared with a 65% reduction for projects using other treatments.
Traffic Calming: Speed Reductions
50th Percentile Speed Reductions
85th Percentile Speed Reductions
Crashes
This analysis covers 29 traffic calming projects spanning 18.6 miles, each with at least one year of post-construction crash data. Comprehensive crash costs declined for 23 projects, increased for five and remained unchanged for one. Together, these locations are seeing 11.0 fewer fatal and injury crashes annually with $11.8 million in total, annual comprehensive crash cost savings—significantly exceeding the projects’ one-time collective construction cost. Based on recent projects, Vision Zero estimates that the current yearly cost-benefit ratio for traffic calming is 2.8 (or $2.80 saved in comprehensive crash costs each year for every $1.00 invested).
Crash Reductions for Traffic Calming Projects Compared to All Level 2 Streets
Crashes
Costs
| Measure | Traffic Calming Projects | All Level 2 Streets |
|---|---|---|
| Fatal and Serious Crashes | 33.4% reduction | 22.0% reduction |
| All Injury Crashes | 51.8% reduction | 32.2% reduction |
| All Crashes | 50.8% reduction | 34.0% reduction |
| Comprehensive Crash Costs | 46.7% reduction | 26.8% reduction |
Traffic calming projects also outperformed citywide crash trends on Level 2 streets over the last ten years when comparing 2016–2020 and 2021–2025. Fatal and serious injury crashes declined 33% on treated streets, compared with 22% on all Level 2 streets. Comprehensive crash costs fell 47% after traffic calming, compared with 27% on Level 2 streets citywide.
These results should also be viewed in the context of broader City investments. Over the past decade, Austin has implemented substantial safety improvements on Level 2 streets—including Neighborhood Bikeways, pedestrian crossings, sidewalks, and urban trails—which likely contributed to citywide safety gains.
Neighborhood Speed Limit Reductions
When Austin’s City Council adopted speed limit reductions on core arterials in 2020, they also lowered the default speed limits for over 800 miles of residential streets to 25 mph, most of which had previously been 30 mph. A yearlong study informed this decision, including a statistical analysis of speed data for a sample of 100 residential streets.
Speeds
TPW first collected speed data on more than 370 residential (i.e., Street Level 1) streets before 2020. In late 2024 and early 2025, follow-up data were collected at 51 locations: 35 streets with new 25 mph speed limit signs and 16 control sites that had not yet received updated signage. The sample included neighborhoods across north, central and south Austin. Besides signage and education, the analysis controlled for other major factors.
Vision Zero also analyzed StreetLight data for the same road segments in 2019 and 2024. Nearly all sites had sufficient data despite having fewer connected vehicles. To assess broader trends, the analysis also included more than 11,000 Level 1 street segments from StreetLight with 25 mph speed limits.
Point and StreetLight data both found lower 85th percentile speeds on treated residential streets, although the estimated effects differed. In the graphic, point data showed speed reductions at both treatment and control sites, with treatment sites averaging an additional 0.6 mph reduction. StreetLight data found a larger treatment effect of 1.44 mph.
Across all Level 1 streets with 25 mph speed limits, StreetLight showed a 0.4 mph reduction in 85th percentile speeds between 2019 and 2024. While the magnitude of change varied by the dataset, both sources indicate that Austin’s neighborhood speed limit reductions are correlated with reduced vehicle speeds.
Neighborhood Speed Limit Reductions
(n=51 Locations)
(n=50 Segments)
Speed Limits
(n=11,889 Segments)
| Data Source | Treatment Change | Control Change | All Level 1 Street Change |
|---|---|---|---|
| Point Data, 51 locations | 4.2 mph reduction | 3.6 mph reduction | Not applicable |
| StreetLight Data, 50 segments | 0.04 mph reduction | 1.4 mph increase | Not applicable |
| Level 1 streets with 25 mph speed limits, 11,889 segments | Not applicable | Not applicable | 0.4 mph reduction |
Crashes
As a proxy for residential areas with new speed limit signs, staff analyzed City-owned, Level 1 streets to track crash data over time. In the five years after City Council approved new speed limits of 25 mph, crashes on residential streets declined when compared to the previous five years: 2016–2020 and 2021–2025. These changes have been associated with as many as 35.6 fewer injury crashes per year and 8.2 fewer fatal and serious injury crashes per year. Annual comprehensive crash costs have fallen along residential streets by as much as 32%, or $42.4 million.
When compared to all other street levels, City-owned, Level 1 streets had a higher percent reduction in fatal and serious injury crashes, at 39%. These Level 1 streets also saw the second-largest percent reduction in total crashes, at 29%.
Changes in Fatal and Serious Injury (KA) Crashes and Total Crashes by Street Level
2016–2020 vs. 2021–2025
KA Crashes
KA Crashes
KA Crashes
KA Crashes
KA Crashes
Total Crashes
Total Crashes
Total Crashes
Total Crashes
Total Crashes
| Street Level | KA Crashes | Total Crashes |
|---|---|---|
| Level 1 | 38.7% reduction | 28.6% reduction |
| Level 2 | 22.0% reduction | 34.0% reduction |
| Level 3 | 13.8% reduction | 23.9% reduction |
| Level 4 | 2.3% reduction | 3.4% reduction |
| Level 5 | 7.0% increase | 1.2% increase |
Discussion and Next Steps
Austin’s speed management strategies—including arterial speed limit reductions, traffic calming and residential speed policy changes—have produced consistent evidence of lower vehicle speeds and improved safety. Although the magnitude of change varies across datasets and individual corridors, the overall direction of the findings is remarkably consistent: interventions reduce speeds and are associated with better safety outcomes.
Both point speed studies and StreetLight connected vehicle data found speed reductions following implementation, while crash analyses—particularly for traffic calming projects—show meaningful reductions in injury crashes and comprehensive crash costs. Together, these results suggest that even modest reductions in average or median speeds can substantially reduce the number of drivers traveling at the highest-risk velocities.
The findings reinforce an important principle of the Safe System approach: While lowering speed limits is an effective tool, changes to the physical design of the street have the greatest and most durable impact on driver behavior. Projects that narrow roadways, add traffic calming or create self-enforcing streets consistently produced the largest speed reductions.
Austin’s experience is consistent with research from other U.S. cities:
- In Portland, reducing speed limits on arterials by 5 to 10 mph resulted in lower mean speeds for 69% of streets.
- San Francisco’s traffic calming projects have reduced 85th percentile speeds by an average of 13%.
- In Boston, decreasing default speed limits from 30 mph to 25 mph led to a 29% drop in the odds of a vehicle exceeding 35 mph.
- In Seattle, lowering speed limits to 25 mph along corridors and in urban centers reduced 85th percentile speeds by 7.1%, crashes by 22% and injury crashes by 18%.
Many cities have also adopted additional speed management tools, such as automated speed enforcement and intelligent speed assistance for repeat speeding offenders, although these strategies are currently limited under Texas law.
This paper focused on traffic calming and speed limit reductions, the core elements of Austin’s Speed Management Program. More broadly, TPW also uses lane conversions to curb speeding and improve safety while maintaining traffic flow. These projects repurpose travel lanes—for example, converting four lanes to three with a center turn lane—to reduce crash risks, lower high-risk speeding, and create space for safer pedestrian crossings, bike lanes, or transit stops. Lane conversion projects in Austin have seen impressive safety results:
- On Bluff Springs Road, high-risk speeding fell 58% and crashes fell 30%.
- On Cameron/Dessau Road, the proportion of drivers going 10 mph or more over the speed limit dropped from 20% to 2% while crashes fell 27%.
- On Barton Springs Road, the number of people exceeding 40 mph declined 64%.
- In Austin, comprehensive crash costs have fallen by 19% after lane conversions.
Analytical Limitations
This analysis identifies strong associations between Austin’s speed management strategies and improved safety outcomes but does not establish direct causation. Many corridors received multiple safety improvements during the study period, making it difficult to isolate the effects of individual treatments, such as speed limit reductions, traffic calming or lane conversions. In addition, crash analyses for individual projects are limited by relatively small sample sizes, particularly for crashes involving pedestrians or people on bikes.
Evaluating long-term safety performance is further complicated by broader changes in driving behavior that occurred alongside Austin’s speed management implementation. According to the AAA Foundation for Traffic Safety, the COVID-19 pandemic contributed to a nationwide increase in speeding, impaired driving and seat belt nonuse, with disproportionate increases in traffic fatalities among people of color and those with lower educational attainment. Austin experienced many of these same trends, culminating in a record number of roadway fatalities in 2022. These external factors make it more difficult to attribute changes in crash outcomes to any single intervention.
Despite these limitations, the consistency of the findings across multiple datasets, intervention types and performance measures provides strong evidence that Austin’s Speed Management Program is reducing vehicle speeds and improving safety. Even where measured speed reductions are modest, they represent meaningful decreases in the frequency of the most dangerous speeding behaviors.
Next Steps
Austin will continue advancing its Safe System approach by pairing context-based speed limits with investments in self-enforcing street design. Future efforts will prioritize traffic calming, lane conversions and other roadway improvements that reduce vehicle speeds and create safer conditions for all road users.
The City will also continue refining its data-driven approach to speed management by prioritizing projects based on crash risk, speeding, equity and surrounding land use. To improve the completeness of safety analyses, Vision Zero is integrating EMS and Fire Department records with police crash reports, providing a more comprehensive understanding of traffic injuries and fatalities.
While traffic fatalities remain a significant challenge, recent trends are encouraging, including a 27% reduction in serious injury crashes from 2024 to 2025. As the City continues delivering projects funded through the 2018 and 2020 mobility bonds, ongoing monitoring will help evaluate performance, guide future investments and ensure Austin’s speed management strategies continue to improve safety.
