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Today's Statesman is full of people whining that "city planners" didn't get Ben White / I-35 right.

For those who still don't get it: NOBODY AT THE CITY OF AUSTIN GETS ONE LICK OF LOUSY INPUT INTO THE DESIGN OF AN INTERCHANGE BETWEEN TWO STATE HIGHWAYS. If the road has a big route number on it (like "2222", "71", "290", "I-35", "US-183"), the city doesn't control the road, and TXDOT doesn't ask for the city's opinion on things.

The sum total of the involvement of the City is to screw with signal timings at intersections with traffic lights, in a few cases. And in most of those cases, the bad design decisions made independently by TXDOT mean that all the signal timing changes in the world won't help.

To whit:

Today I biked to work. (Well, I biked to the bus to work; I'll be biking all the way home). I forgot to pack my lunch. I had a bunch of leftover change in my bike bag, so I walked along this route to the local McDonald's to get a cheap greasy lunch.

I noticed a pretty long backup, as always, at the Braker intersection. Today, I ended up passing the same stopped cars a couple of times; so I started paying attention. Guess what? I was able to beat a car in the right lane ON FOOT from my office to the other side of the Braker intersection. This wasn't a twenty-foot trek either. According to Yahoo, this is a quarter-mile jaunt.

Why is this intersection so bad? Why is Ben White's rebuild so painful? Two words: frontage roads. When TXDOT 'builds' a freeway, they're actually (9 times out of 10) turning an existing arterial roadway (with driveways, strip malls, etc) into a freeway by using the original roadspace for the new main lanes and then widening into property on the sides to build "frontage roads" (one-way streets which the main lanes exit to and enter from).

So what are the problems with frontage roads?

  1. They generate their own traffic - cities (who had to give up a ton of land, and in most cases even PAY for the pleasure) aren't going to restrict future development along these streets, especially since TXDOT sells them on the idea that they should keep doing so.
  2. They cause poor intersection design. Most intersection with frontage roads must operate with four independent cycles - meaning that the people arriving from each of 4 directions are given exclusive use of the intersection on their green light. (The "intersection" in this case extends to both frontage roads). Two major two-way arterials which intersect, on the other hand, operate with two cycles (one for each road) with minor additional cycles for left turns.
  3. They preclude better interchanges down the road - unless it's to another freeway. In other states, the intersection at Braker would have long since been upgraded with more space, possibly changed to a SPUI (single-point urban interchange which reduces traffic signal cycles to essentially 3), or possibly improved with a ramp modification, or even adding one or two flyovers... but not here. Here, we're stuck the way we are. On Ben White, you can build a direct connector ramp (flyover) since there's another freeway on the other side. On Braker, building a flyover would mean bulldozing everything on one corner of the intersection that located there because of the frontage road.
  4. They actively exclude cyclists, pedestrians, and transit users. Typically fewer crossings are built or preserved on highways with frontage roads (example: US 183 between Spicewood Springs and 620). This is a minor irritant to motorists but completely screws other users of the roadway, since it's not practical for them to walk a mile down the road, cross at the only remaining crossing for a mile either way (Anderson Mill), and walk back.

What should TXDOT have done in these cases?

Simple: either toughen up and just admit that we can't preserve property access on what's supposed to be a limited-access highway, or do what they do in other states - build perimeter roads (that maintain property access from the city streets, not directly from the highway) rather than frontage roads. This would run counter to the ethos that highway construction and expansion exists to promote retail traffic, which is why it'll never happen in this state, but that's what it would take.

This entry was posted in the following categories: Austin , Driving in Austin , Funding of Transportation , Texas Republicans Hate Cities


I have lived in indianapolis my whole life where there are no frontage roads. It is about the same size as Austin. Every urban interchange between an interstate and major road is usually cloverleaf or diamond-style. I wasn't used to the frontage road situation until I came to Texas.

In my opinion the frontage roads allow much quicker access to a major artery and they also allow for much more efficient real estate usage along the freeway. So you get a tradeoff between moving cars and convenience. The concept is great, but moving traffic on and off of a major thoroughfare is not as efficient.

Basically traffic in Austin just sucks. There are too many drivers, too many unneeded signals that are timed improperly. There aren't enough on- and offramps where they are needed. The lights on the frontage roads seem to be biased to traffic perpendicular to the freeway - eg. traffic going to the other side, instead of being biased in favor of the north-south traffic on 35.

The city and state are constantly messing with the timing of lights at frontage road intersections (this is one of the few places where the city can do ANYTHING relating to a state highway), and fundamentally it's NOT a matter of bias for through traffic.

(I-35 is a bit different because parts of it are so old that the passage across is very short - allowing more of a traditional 3-cycle traffic-signal design in central Austin, for instance).

Better to look at the modern designs where the freeway is quite wide, since that's what new ones are going to look like, and it's not pretty. The necessity for 4 completely isolated cycles (instead of 2, 2+turns, 3, 3+turns, whatever) really hurts the ability to handle more than minimal traffic.

Take a look at 183/Braker, or I-35/Parmer, or Mopac/Parmer, for the most obvious examples of this problem. No matter how much time you give one movement, you still have four separate movements, so the wait for somebody is going to be quite quite long.

I hate frontage roads. They're ugly and inconvenient.

I think they're built because it's a bang for the buck thing. The state can move lots of traffic and it doesn't have to build expensive bridges and interchanges. Cities like them because they don't have to pay for the construction. It also increases the value of property (tax base) to which the frontage is attached. For that reason, landholders along the freeway also like frontage roads.

Do you know what happens when TxDot doesn't want to build a frontage road? The city cries out for one. Look at what happened during the planning for I69, which is, last I heard, being planned with no frontage roads.