What Goes on Top of a Highway?

An illustration prepared as part of an engineering study of the caps and stitches over I-35 shows mostly park space, along with small buildings possible at the edges of the caps. Image: Atkins / City of Austin

The widening and lowering of Interstate 35 in Central Austin isn’t gonna be pretty. Estimated construction times for the Texas Department of Transportation’s so-called Capital Express project hover at around eight years, and will likely take place concurrently with the voter-approved construction of Project Connect’s rail lines and other transit improvements — you should probably plan on avoiding traffic for roughly a decade once everything kicks off. But while Project Connect at least has a train at the end of the tunnel, the I-35 expansion just brings us more lanes, and the local search for a silver lining is currently centered on potentially “capping and stitching” the newly-sunken highway largely at the city’s expense to at least partially bridge the gap I-35 creates between East Austin and the downtown area. 

Image: City of Austin

As you might imagine, a lot of details remain firmly up in the air, with the city currently seeking public feedback as plans move forward. But lately we’re wondering about a more fundamental detail of these caps, which are estimated to reclaim something like 15 acres of space over the highway — what do we put on top of them? The immediate answer is “parks,” and most illustrations of the design simply show the caps covered with empty green space, but we’re not convinced.

That’s a lot of green — but what else should we do? Image: Texas Department of Transportation

A 15-acre linear park a block away from the far more interesting Waterloo Greenway doesn’t sound particularly engaging, and with some estimates putting the price tag of the caps and stitches at around $800 million, we’re not sure that’s gonna cut it. A study of the potential project by global engineering firm Atkins indicates that the new area over the highway will only be structurally capable of supporting one or two-story buildings at most, and only near the edges of the caps — so a big commercial development to recoup some of that cost is largely out of the question. 

1/ PLANS TO WIDEN I-35 have been narrowed by TxDOT from two designs to one. You can leave a public comment on the project until March 7, so here's some of what TxDOT prefers to do. https://t.co/AHeKOThA7n

— Nathan Bernier (@KUTnathan) January 4, 2023

With these limitations in mind, and the design process currently still in a sort of napkin scrawl phase, we figured we’d pose the question to you, our handsome and intelligent readers — what goes on top of a highway? Less glibly, what is the highest and best use of the reclaimed land over I-35 considering the engineering limitations and cost estimate we’ve heard? If the answer is a large park, how should that park be amenitized and programmed to distinguish it from the nearby Waterloo Greenway? There’s a lot to consider here and we’d like to hear your ideas, since the whole I-35 situation currently doesn’t give us much in the way of excitement. Get to it: