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Vehicle Miles Traveled

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24.8 Daily vehicle miles traveled per capita in Travis County in 2014

Indicator: Vehicle miles traveled per capita in Travis County

Goal: Reduce vehicle miles traveled per capita in Travis County

Target: 21 daily vehicle miles traveled per capita by 2020

Key Trends: Daily vehicle miles traveled (VMT) per capita in Travis County increased in 2014, after several years of trending downward, and is now higher than it was in 2010. A higher number of miles driven by individuals on a daily basis, combined with population growth, means many more cars on our roadways, resulting in more congestion, more air pollution, and a poorer quality of life. Daily VMT has increased across suburban counties in the Austin area as well, but at an even faster rate. Counties without large employment bases have the highest VMT rates. Population growth, coupled with people driving greater distances to get to work, translates to more congestion. This increase in traffic congestion has landed six Austin corridors on the INRIX 2015 Traffic Scorecard’s 100 most congested traffic corridors in the nation.

what the data tell us

In 2014, daily vehicle miles traveled (VMT) per capita increased to 24.8 in Travis County from 23.0 in 2013. Over the past seven years of reported data, the number of miles driven by individuals on a daily basis, experienced a relatively steady decline, until the uptick in 2014.

Daily VMT has increased across suburban counties in the Austin area as well, but at an even faster rate. As suburban populations continue to grow and jobs continue to locate centrally in the metropolitan area, the number of miles driven by individuals on a daily basis has continued to rise. The Capital Area Council of Governments reports that the majority of people living in the counties listed below, with the exception of Travis County, live and work in two different counties. Research by the Texas Transportation Institute found that about 86% of traffic on Interstate 35 in Central Texas is caused by local traffic.

Definition: Daily vehicle miles traveled on public roads divided by population

Data Source: Texas Department of Transportation (TxDOT)

Data Considerations: VMT reflects miles driven by both personal vehicles and commercial vehicles including freight trucks.  VMT is calculated by TxDOT based on traffic counts collected using permanent counters on some roadways as well as regular saturation counts of major roadways on and off the state highway system. The actual miles driven by residents in the region may be lower or higher than average daily VMT per capita. In 2014, traffic-related data was the result of a new data system. Based on this information, statewide VMT decreased by 1.5% when compared to the 2013 data. This is contrary to local VMT trends.

the story behind the indicator

In recent years, vehicle miles traveled (VMT) per capita have declined steadily in Travis County, but increased in the most recent data. The two major job centers in the Austin MSA are Austin and Round Rock, and their counties—Travis and Williamson—have the lowest VMT per capita in the five-county MSA. Counties without large employment bases have the highest VMT rates. The Capital Area Council of Governments’ Housing Opportunity in Central Texas report notes that, “With the exception of Travis County, a majority of workers in every county in the Austin metropolitan area are employed outside of their home county.”

Traffic, roads, and transportation were a top concern for Austin area residents in the 2015 Zandan Poll with 82% citing it as top issue facing Austin. When asked what Austin has lost due to growth, 23% reported ease of transportation. Traffic congestion is a closely related issue to VMT and has grown steadily worse over time in the Austin area. As of 2015, eight of the state’s 100 most congested roadways were located in Travis County, according to the Texas Department of Transportation.

The Washington State Department of Transportationidentified three main strategies for reducing vehicle miles traveled:
1) Shift modes; 2) Increase vehicle occupancy; and 3) Travel less.

In 2014, about 75% of Travis County workers and 77% of workers in the 5-county Austin MSA drove alone to work, according to the American Community Survey. Approximately 10% of workers in both jurisdictions carpooled to work and about 7% of workers worked from home, a higher percentage than in the state and nation as a whole. Workers also utilized more active modes of transportation including walking, biking and public transit. In 2014, about 8% of City of Austin residents commuted to work using public transportation, a bicycle, or by walking, compared to about 5% in the 5-county area. In Travis County, 4% of workers used public transportation, 1% biked, and 2% walked to work.

The Centers for Disease Control notes that lower VMT results in lower emissions, improving respiratory and cardiovascular health. Lowering VMT by shifting to more active forms of transportation can also improve health by encouraging physical activity. The Gallup-Healthways Well-Being Index reports a wide range of adverse physical and emotional conditions resulting from long commute times. Longer commutes to and from work also impose on family time and time available to be engaged in the neighborhoods and communities where people live. They also have a significant impact on household affordability, as transportation is typically a household’s second largest expense.

a closer look

Click on one of the titles below for more information.

» Commuting mode-share, excluding "Drove Alone" Workers 16 and over, 2014

The majority of commuters in all jurisdictions below drive alone to work. In 2014, about 75% of Travis County workers commuted to work alone. The graph below shows the share of workers utilizing other means of transportation to get to work. After driving alone, the second most common method of commuting in all jurisdictions involves commuting via two-person carpool. Notably, workers in the Austin-area are much more likely to work from home than workers in both the nation and Texas as a whole. In 2014, about 7% of workers primarily worked from home. Perhaps expectedly, residents of the City of Austin area are more likely than residents of the overall metropolitan area to use active transportation. In 2014, about 8% of residents of the City of Austin commuted to work using public transportation, a bicycle, or by walking, compared to about 5% in the 5-county area. In Travis County, 4% of workers used public transportation, 1% biked, and 2% walked to work.

Definition: The percentage of workers, ages 16 and over, who commute to work using a given mode of transportation

Data Source: American Community Survey, 1 Year Estimates.

Data Considerations: The American Community Survey samples 3% of the Nation’s population. Due to small sample sizes, margins of error are increased and hard to reach populations may not be accurately represented in the data. American Community Survey data are collected continuously throughout the year. For questions related to means of transportation, survey respondents are asked to consider a “reference week”, the week immediately before they were surveyed, and answer accordingly. ‘Means of transportation’ refers to the principle mode used to commute to work. Survey respondents who commute to multiple workplaces or use multiple modes of transportation are asked to choose their primary workplace and mode of transportation used for the longest period of time. The data, therefore, do not reflect all modes of transportation utilized and only capture the means of transportation used to commute to work.

» travel time index

Congestion results in a significant amount of lost time for Austin-area commuters. In 2014, the Austin area’s travel time index stood at 1.33. This means that an average commute in Austin takes 33% longer during peak traffic periods. A commute that takes an hour in free-flowing traffic takes about an hour and a half during peak periods. Austin’s travel time index has grown progressively worse over the years, passing the national average in every year since the early 1990s. Houston is the only other major urban city in Texas that has a Travel Time Index as high as Austin.

Definition: The Travel Time Index, calculated by the Texas Transportation Institute for the Austin Urban Area and the average Index for 498 urban areas across the nation

Data Source: Texas Transportation Institute, Urban Mobility Report

Data Considerations: A measure of congestion that focuses on each trip and each mile of travel. It is calculated as the ratio of travel time in the peak period to travel time in free-flow. A value of 1.30 indicates a 20-minute free-flow trip takes 26 minutes in the peak.

» annual delay per peak auto commuter

The average Austin commuter who drives during peak hours loses about 52 hours each year to congestion. Austinites have lost more time in traffic than drivers nationwide every year since 2000. Although the average time lost declined throughout the mid-2000s, it rose again from 2010 to 2014. In 2014, the average driver in the nation lost 42 hours in traffic. Of Texas’ major urban cities, Houston’s commuters lost the most amount of time in 2014 (61 hours), and Dallas and Austin commuters came in a close second and third at 53 and 52 hours respectively.

Definition: Hours lost each year per peak-hour commuter due to congestion

Data Source: Texas Transportation Institute, Urban Mobility Report.

Data Considerations: A yearly sum of all the per-trip delays for those persons who travel in the peak period (6 to 10 a.m. and 3 to 7 p.m.). This measure illustrates the effect of the per-mile congestion as well as the length of each trip.

» map of ranks of Austin's roadways among the most congested in the state

The Texas Department of Transportation, in partnership with Texas A&M’s Texas Transportation Institute, ranked Texas’ 100 most-congested roadways as of October 29, 2015. The map below, from TXDOT, shows the ranks of Austin’s roadways among the 100 most congested in the state. Interstate 35 and MOPAC/Loop 1 are currently Austin’s most congested roadways. TXDOT estimates that congestion on IH 35 costs about $136 million annually and congestion on MOPAC amounts to almost $75 million annually.

Definition: Austin-area roads that are among the Texas Department of Transportation’s top 100 congested roadway segments, as of August 31, 2014

Data Source: Texas Transportation Institute, Texas Department of Transportation.

Data Considerations: The methodology for determining the top congested roadway segments is available here.

some local efforts to improve this indicator

Collaborative Initiatives

Several initiatives are reshaping roadways in the Austin area:

Plans, Data, and Reports

vulnerable populations

People Living in Suburban and Rural Areas of the Region — A 2012 report by the Brookings Institution found that only 30.1% of the overall population and 7.4% of the suburban population of the Austin-Round Rock metro area can reach the typical job in 90 minutes via public transit.

The Elderly, Disabled, and Poor — The Austin/Travis County Community Health Improvement Plan found that the elderly, disabled, and poor in our community are disproportionately impacted by transportation challenges.