Has Austin built enough roads?
Has the Austin region caused worse traffic by not building enough roads?

Jay Blazek Crossley, Farm&City

Responding to a prompt from Tom Wald


There is a myth that local decision makers have somehow denied the people of Austin the roads that they deserve, causing the people of Austin to suffer more from traffic than others and more than they would be suffering today if these poor decisions had not been made.

This creation myth is used extensively to spend money on building roads in the Austin region.

How much has TXDOT been spending in the Austin region?

Looking at the six-county CAMPO region, TXDOT spent $3,723,542,837 on construction and $1,621,263,818 on maintenance from 2006 through 2015. At $284 per person per year, TXDOT spent more per person in the Austin region than in Houston, DFW, San Antonio, Hidalgo County, Corpus Christi, or Brownsville. Compared to the Austin region, TXDOT only spent more on people in El Paso, Killeen-Temple, and all smaller metro areas and rural areas.

73% of the people of Texas live in those six large MPOs that did not enjoy as much TXDOT spending as the Austin region.

Looking at just the construction side, TXDOT spent a little more per person in the Austin region than in the smaller metros and rural areas of the state (the “Rest of State”). So in terms of building new things, the only parts of Texas that got more funding per capita than the Austin region for the decade ending in 2015 were Killeen-Temple – home to one of the worlds largest military bases – and El Paso – home to the Democrat who as Chair of the Texas House Committee on Transportation oversaw the Texas Republican Party’s major accomplishment this century, going from zero in TXDOT debt on the last day of Governor George W. Bush to $21 Billion in 2017, almost all spent on new roads.

So how many miles of road do we have in Austin?

Roads can be measured in lane miles. If your county has only one road that is one mile long and has four lanes (two on each side), then you have four total lane miles in your county. According to TXDOT, Texas has 195,964 lane miles. At perigee – its closest point – the Earth’s moon is 225,623 miles from us. In 2016, Texas had 195,767 lane miles. At this pace of growth, Texas will reach the moon in year 2168.

The 6-county Austin region is home to 6,878 lane miles – only 4% of the state’s quest to get to the moon, but 14% of the lane miles we have in the 9 large MPOs, which are home to 75% of Texans and 84% of Texas’ GDP. Generally, people in Austin think they are comparing it to other major Metropolitan areas when they complain that roads aren’t keeping up with growth. There are vast miles of long roads across this big ole state of ours, which means that 75% of the lane miles in Texas are in all those counties where the other 25% of Texans live - in rural or small metro areas.

When we look at the nine large MPOs in Texas, the Austin region has more lane miles per capita than Dallas - Fort Worth, El Paso, Houston, San Antonio, and Hidalgo County. Only Brownsville, Corpus Christi, and Killeen-Temple have higher rates of lane miles per capita than Austin.

Austin has 54% of the lane miles that the entire DFW region has, but only 29% as many humans.

So what’s the deal with traffic then – if we’ve been blessed with all these roads?

People in Austin think that Austin has bad traffic. The grass is greener. More vehicles drive on Houston’s I-59 Southwest Freeway every single day (341,309) than on Austin’s I-35 (198,682) and Mopac (134,486) combined, and the I-10 Katy Freeway - Houston’s next busiest freeway segment carries another 320,695 vehicles every day.

But Austinites are actually correct in their hunch that traffic is somehow worse in Austin than other Texas cities, even though there is a lot less total amount of it.

Traffic is really measured in vehicle miles traveled. Every single vehicle in a place times how far each one goes on an average day. TXDOT reports VMT by county on TXDOT “on-system” roads. Of the 707.2 million miles driven every day in Texas, 515.9 of them are done “on-system”. So we can compare driving in the different metro areas of Texas using TXDOT’s DISCOS data, but it is important to remember that this does not include driving on local streets and toll roads operated outside of TXDOT’s system.

When we look at VMT per capita in Texas MPOs, Austin again comes out on the bad end of the chart. We drive more than most other Texans, except for those living in the Corpus Christi and Killeen-Temple metro areas, small metros, and rural areas.

People in Dallas and Houston drive less on average – every single day – than people in Austin. More vehicle miles traveled per capita means each one of us actually takes up more space on the roads of the Austin region than our fellow citizens in Houston, Dallas, and San Antonio take up on their lane miles, which translates to more traffic.

We are the traffic.

There is a widespread belief among some traffic engineers and urban planners that building additional roadway capacity causes people to drive more. It could be they have a point. It could be that Austin actually has more roads per capita than other Texas cities and that we all drive more than we would otherwise if we hadn’t built so many roads.

But what about toll roads?

The Austin area is home to two toll road systems, the Central Texas Turnpike System – financed and controlled by TXDOT and the toll roads built and operated by the Central Texas Regional Mobility Authority.

The data in the section above on TXDOT spending comes from their annual DISCOS (District and County Statistics) report, which includes data on costs, lane miles, and vehicle miles traveled, but only on the TXDOT “on-system” roads. This includes major highways, but also many major urban arterials, such as sections of North Lamar in Austin. CTRMA toll roads are not included in these numbers, but I am not sure whether or not the Central Texas Turnpike System is included as “on-system” roads.

Further iterations of this work will look into the costs, lane miles, and vehicle miles traveled on Texas toll roads.

Is Austin sprawled out or something? It’s nowhere as big as Houston?

Yada yada, yes it is.

Spoiler alert: New data set confirms above story, but digging in deeper

After writing this draft above, I was surprised to find this page on TXDOT's website. I've been looking at these kinds of stats for two years, including somewhat long email exchanges with TXDOT staff asking for all the data they have on VMT, but never was shown or found this. So it's exciting. This is a treasure trove of data.

Here is Daily average VMT in each major Texas metro area, not just on the txdot roads, but on all roads. The people of Austin drive more than most Texans, but not quite as much as Killeen-Temple, Corpus Christi, and rural and small metro areas.

With this data (no really this excel is just a remarkable set of data), I think we can get at some things I've wanted to do for a long time, if my friend Omar Chavez can help us with the data science methodology: We can likely use time-series analysis to examine the impact of lane miles per capita on vehicle miles traveled per capita, the age old induced demand question.

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