Texas is planning on installing their first modern roundabout on an Interstate frontage road near me, at 51st and I-35. Just east of the intersection is my development, the old Austin airport, that will at full build house ~10,000 people and employ ~10,000 people. The development includes big box retail, the area’s children’s hospital, medical research campus, “town center” walkable commercial, etc.
Per TxDOT, the traffic load for the intersection being rebuilt is projected to increase so much by 2020 that they would need to build a triple left-turn lane to keep it flowing under the traditional model. Instead, they propose adding an Interstate bypass lane for frontage road traffic not needing 51st St access and a roundabout that looks pretty intelligent at first look.
This intersection, though, has seen a lot of changes over the year, mostly negatively impacting the intersection.
Using Google Earth as a guide, let’s look back at the history of this intersection.
To orient a bit, the lower-right corner is the then-operational Austin Mueller airport. IH-35 is running north to south, top to bottom. 51st is running east to west, right to left across the screen roughly. Cameron Rd is spurring off to the northeast at this same point.
I’m pretty sure that pre-IH-35, Cameron Rd was a bigger deal than it is today.
To explain the intersection, we have a few fun pieces going on. Northbound IH-35 frontage road splits near the bottom of the picture. The left split is a bypass under 51st and continues along the highway. The right split hits a traffic signal at 51st and continues on as Cameron Rd.
If you were traveling south on Cameron Rd toward that intersection, you have the option of staying left to hit the traditional intersection to turn left or right onto 51st, or you could go right and choose a fancy slight right onto 51st or a direct onramp onto IH-35 courtesy of the near loop.
51st Street traffic could still access SB IH-35 via a traditional onramp south of the intersection. NB traffic could turn onto NB Cameron, then left to a short little snub of 53rd Street that connected to the NB IH-35 frontage road.
For reasons that I don’t know enough of the history of, there is a fancy U-turn for southbound IH-35 frontage onto the northbound lanes that goes over the Cameron->SB IH-35 loop onramp and connected with the NB bypass lane.
Phew. I think that’s everything going on here.
By 2002, the next image Google Earth has available, a couple of things have changed. First, the airport is now closed with plans for redevelopment starting, but no dirt moved yet. Just north of our frame, a set of direct connect ramps for U.S. 290 were built, adding a large number of merging cars onto IH-35.
My understanding is, because of this, they closed the direct on-ramp from Cameron to SB IH-35 as on-ramps from 290, Cameron, and 51st would be too much in a short distance to remain safe.
This increases the type of traffic that would hit the 51st and I-35 intersection.
Slight change here. The slight-right over the special bridge from Cameron to 51st is closed. I’m unsure of the rationale at the time.
2005 shows us the silliest change in my opinion. The old airport is officially being redeveloped and the first roads on going in. A new road, Barbara Jordan Blvd, begins perpendicular to IH-35 near the bottom of the picture running east (right). They build it making the right-turn onto Barbara Jordan as a replacement to the spur direct to the 51st/Cameron intersection.
Now, all traffic wanting to access 51st Street or Cameron must now take a right into the new development through a shopping district, then take an extra turn to then reach 51st Street. Worse, if you were trying to go to Cameron, which used to be direct with a traffic signal, you have to turn on 51st, then turn onto Cameron. Four turns instead of none.
They called this the jughandle, which I don’t think is terribly unfair that in retrospect it was a jughead of an idea.
No changes here, except that the retail space is built out now. The direct access ramp to Cameron was eliminated for a corner of a parking lot.
Two things: TxDOT removed the slight-right from westbound 51st to Cameron Road, in the name of improved access for cyclists and pedestrians, which has had the side effect of longer lines at the intersection.
The fun thing: TxDOT is finishing a new way to directly access Cameron Road. Let’s zoom in.
TxDOT destroyed the long-closed Cameron->51st slight-right bridge, added a poorly marked exit from the frontage road to a hard right turn into an intersection with Cameron.
This is still painful for 51st Street access—traffic backs up on Cameron pretty often and this only adds to it, but I suppose better than the old way.
With the roundabout, they’re fixing the other side of the highway from this intersection, which should really help in many ways, but I’m afraid that they’ve set themselves up for needing a total rebuild of Cameron and 51st in a similar style as this Frankenstein approach has, so far, been applying bandaids to a broken dam.
2025 Update
January 28, 2025
The roundabout opened!
All in all, it looked pretty good. The long-closed direct access bridge from Cameron to 51st partially hung around, with the new NB 35 to Cameron connection open.
Businesses along the southbound frontage road gained a little access road. The intersection there with 52nd Street is blocked so there’s no access to this stub except for the frontage road.
One negative thing—the sliplane from SB frontage to WB 51st that allowed traffic to take that turn without entering the traffic circle created two issues:
- 51st Street was slated (and done) to go on a lane diet to one lane with the merge needing to happen right there.
- The turn to Harmon Ave (the small street just west of the traffic circle off of 51st) was perilous. People coming through the traffic circle would turn across the sliplane traffic, usually too fast. I didn’t look up the crash data, but driving it, it wasn’t ideal.
TxDOT did close the sliplane (not reflected on Google Earth screenshot above) so all must enter the traffic circle now.
The Future
With IH-35 being rebuilt through Central Austin, this intersection isn’t slated to see that much change.
Rotating the original to match the orientation of the images above, the traffic circle is untouched. There will be a new u-turn from NB frontage to SB frontage, and the existing SB to NB will be rebuilt. The Cameron Road access segment will be rebuilt and realigned. The shared use trail will be new, though on the east side, there is already a trail alongside Mueller (The Home Depot). The mainlanes will see a new on-ramp to NB IH-35. The marked new exit for SB is already present, so I’m unsure why it is marked new.
While there will be more changes around Airport Blvd and further south, TxDOT seems generally happy with their roundabout and related changes to this intersection.
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