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Why was I-35 designed as a double-decker through Central Austin?

 The I-35 corridor
Gabriel C. Pérez
When the upper decks of Interstate 35 opened in 1975, they were the only lanes of that type in the country.

This story was originally published on January 19, 2018.

Interstate Highway 35 is many things to many people. It is a vital thoroughfare for commerce and shipping. It is also an economic and social barrier through much of Austin. And nearly from its construction, it has been a source of frustration for drivers stuck in its traffic. I-35 has inspired a number of questions and even legends about its design and those who made it.

First of all, most of the legends – if not all – aren’t true. One that has been floating around for decades is that the person who designed I-35 committed suicide because of the havoc unleashed upon the city with its opening. To be clear, no one who had any role in designing or constructing the upper decks of I-35 committed suicide – at least to anyone’s knowledge.

 Javier Palomares asked our ATXplained project why Interstate 35 is a double-decker through Central Austin.
Credit Gabriel C. Pérez / KUT
Javier Palomares asked our ATXplained project why Interstate 35 is a double-decker through Central Austin.

Secondly, I-35 in the Austin area is not the deadliest stretch of highway in the United States – or even in Texas. In research published last year by the Ross Law Group, Austin’s stretch of 35, all 14 miles, came in at 45th worst in Texas. The research found two other area highways, U.S. 183 and S.H. 71, statistically more deadly than I-35. None in Austin are in the top 10 deadliest.

The interstate is, however, one of the most congested. One of the solutions to ease that traffic congestion more than 50 years ago inspired a question from listener Javier Palomares:

“Why was I-35 designed as a double decker through Central Austin, instead of a wider highway?” the software engineer asked. “As far as I know, there are not many cities that have a highway running through it that was designed in the 1960s and it’s actually a double-decker.”

He’s right. There are not many highways with four lanes over two decks. Conventional highway construction would likely require officials to forcibly buy more nearby property and widen the roadway.

The Interregional

I-35 was initially part of the interregional highway system, built under the Federal-Aid Highway Act of 1944. America was trying to catch up to what World War II soldiers had seen in Germany: an interconnected freeway that could quickly transport troops and supplies … and cars. By 1952, the first leg of “the Interregional” had sprouted in Austin – the stretch between Airport Boulevard and what was then 19th Street (what’s now Martin Luther King Jr. Boulevard).

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By the late ’50s, on what was then called the Interstate Highway system, you could drive from the southern city limits at Slaughter Creek to the northern city limits without leaving the Interregional. Remember, this was when highways were the future!

What was quite revolutionary for the time was that you could go all the way through town without leaving the highway, but not without stopping.

“Austin at the time had a railroad across 35,” Ben Alley Jr. told KUT before he passed away in 2019. “We were the only city I believe in the country that had railroad stops on a freeway.”

Credit Courtesy of the Alley family
Ben "Benny" Alley Sr. examines a portion of I-35 blacktop.

Alley’s dad, Ben “Benny” Alley Sr., was the assistant district engineer at the State Highway Department. As it happens, the Highway Department realized that it was quickly running out of capacity on 35. Alley Sr., who passed away in 2011, was among those who took the lead on the project to get the Interregional over the railroad and get more cars through Central Austin.

“They couldn’t build 35 wider because of the easements,” Alley Jr. said. “That would cost a fortune. They would have had to purchase all the properties on either side of 35. Building a three-lane highway on one pillar was an engineering feat.”

When the path for 35 was initially laid, planners assumed four lanes and 200 feet would be all that would ever be needed. That left Alley and the highway department one choice at the time: to go up.

'An Ugly Scar'

When the upper decks opened in 1975, they were the only lanes of that type in the country. In highway terms, this was a huge splash, one that other futuristic metropolises – like San Antonio and New Orleans – tried to emulate.

But one man’s engineering treasure, is another’s trash.

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“It cuts a horrible swath through the city of Austin,” said state Sen. Kirk Watson (D-Austin). “It is – at best – an ugly scar that runs right through the city.”

For years, Watson has been trying to figure out how to reduce I-35’s visual and social impact, while helping it move traffic.

“That roadway has probably been cussed by more people than virtually any other segment of roadway in America,” he said. “And so something had to be done.”

What is not in I-35’s future through that stretch is more lanes.

“If tomorrow you had the money, if the state of Texas said, ‘We’ve got the billions of dollars necessary to just go out and build you four new lanes of capacity,’ those would be congested very soon,” Watson said. “All the studies and all the experience across the country tells you they would be congested almost immediately.”

And for now, the future of the Interregional is not up, but down.

“We don’t have right of way,” he said. “You can’t take out cemeteries. You can’t take out downtown. You can’t take out the University of Texas. So what do you do? Well, we don’t want to go up, because that adds to the scar. Instead what this would do is it would put much of that below grade.”

There’s a long-range plan to lower parts of 35 through downtown and beyond. That would mean removing the upper decks completely and putting toll lanes under the existing frontage road.

The Roads Less Traveled

Would Ben Alley Jr. be upset if one of his dad’s signature projects were removed?

Credit Jimmy Maas / KUT
Ben Alley Jr., and his wife, Helen, pose outside their Austin home.

“He knew early on that this wasn’t going to be the big fix for I-35 traffic,” he said. “Even after it was built, it was pretty obsolete.”

Benny Alley Sr., will have other legacies to lean on. He helped design MoPac, Loop 360 and the Pennybacker Bridge.

The Alley family has their own memories, including long drives.

“Whenever we traveled with him, we never took main roads,” said Helen Alley, his daughter-in-law. “It’s very interesting because he worked on main roads, but we always took back roads in Texas, because he loved the countryside and the beauty of it.”

“Not just in Texas, when we would travel anywhere out of state, far north, it was always back roads,” Alley Jr. said.

You see, one of the lead engineers on some of Austin’s seminal highways, did not prefer to drive on the highway.


Jimmy is the assistant program director, but still reports on business and sports every now and then. Got a tip? Email him at Follow him on Twitter @maasdinero.
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