TxDOT practices

[TXtoNJ]

I have a few questions about TxDOT practices that I figured y'all might have some insight on:

1. Why has TxDOT historically shied away from express-local configurations? This is starting to change through the use of tolled express lanes (especially the new 635 design), but even the Katy Freeway had a sort of half-implemented express-local design. The major exceptions are the double-deck San Antonio and Austin segments (and even the Gulf Freeway near downtown, to an extent), but these seemed to be designed more on account of space constraints, rather than design preference.

I think about the weaving mess that is this and wonder what the thought was: https://www.google.com/maps/@29.7260869,-95.4712181,194m/data=!3m1!1e3

2. Particularly in the Houston area, there's a design preference for running the freeway over the cross streets, rather than the reverse. While this seems to be the more expensive option, I imagine this makes things easier due to the omnipresent frontage roads. The constant elevation changes seem to have a particularly negative impact on traffic flow at peak times. Any further reasons for this?

[dfwmapper]

For 2, there are a lot of potential reasons. Bridge costs are typically less because of the extra area needed for the turnarounds. Trenching the freeway isn't always a viable option because of soil stability and water table issues. In some cases, the frontage roads and cross streets were built years before the freeway, and elevating the freeway allowed it to be constructed with minimal disruption to the existing roads.

[aboges26]

1.  I would not say that TxDOT has shied away from express-local configurations, be cause the frontage road system serves as a crude express-local configuration, but an extensive express-local system nevertheless.  Space constrains due to frontage roads and the cost of maintaining a vast network, thus money spread thin, are the main reasons for the lack of true express-local configurations.

2.  Houston gets tropical storms, hurricanes, and enough heavy rain throughout the year.  As such, depressed freeways would be rivers during such events and would be a threat to drivers.

[txstateends]

Case-in-point:  Since US 59 (pre- I-69) got redone in the Montrose area just SW of downtown, heavy rains make a mess of that area.  Overheads there, while not as pleasing to some, would have avoided at least some of the heavy-rain issues.

[DJStephens]

Water table issues, for sure.  Overpassing existing streets and building MSE walls is a lot easier and cheaper than constructing depressing cross sections that have waterproofing.   

[TXtoNJ]

1.  I would not say that TxDOT has shied away from express-local configurations, be cause the frontage road system serves as a crude express-local configuration, but an extensive express-local system nevertheless.  Space constrains due to frontage roads and the cost of maintaining a vast network, thus money spread thin, are the main reasons for the lack of true express-local configurations.

2.  Houston gets tropical storms, hurricanes, and enough heavy rain throughout the year.  As such, depressed freeways would be rivers during such events and would be a threat to drivers.

True, but I was more thinking of keeping the freeway at grade, and running cross streets above grade.

[MaxConcrete]

1. Why has TxDOT historically shied away from express-local configurations? ...

2. Particularly in the Houston area, there's a design preference for running the freeway over the cross streets, rather than the reverse. ... Any further reasons for this?

1. I don't know of an official reason for TxDOT standards regarding express-local. But as you mention, this aversion to express-local has been around since the 1950s, and I think it is just continued as a design practice, whether it makes sense or not.

One possible reason is the right-of-way width issue. Back in the 1950s it was normal to acquire 300-foot-wide corridors, sometimes slightly wider (maybe up to 350 feet) but rarely any wider. This provides space for an 8-lane freeway with 6-lane frontage roads, but not much else. Of course 300 feet is much too narrow to support today's needs (which need 400 to 500 feet), and the major cities are paying a heavy price for the lack of right-of-way, with huge costs to expand corridors, or widening becoming cost prohibitive or politically infeasible.

But the reason right-of-way is so narrow is because funds were very tight in the 1950s, particularly before 1956 when local governments were required to pay for most right-of-way. So they reduced the right-of-way requirement to the minimum feasible (300 feet). Both frontage roads and express lanes could not fit in that corridor width, so express lanes were on the losing end of the choice since frontage roads always take precedence in Texas.

As for the location you cited (Southwest Freeway at Chimney Rock), TxDOT has near-term plans to minimize weaving in the outbound direction by building a new, long exit ramp to Chimney Rock which splits from the main lanes inside the loop.

2. As for Houston freeways always going over the cross streets, I think a big factor is the adjacent landowner's preference for accessibility. With the cross street going over the freeway, more right-of-way is required (costing more money and potentially generating more opposition), but more importantly the property on the four corners is not as conveniently accessible. Landowners like the corner with easy access from the frontage road and the cross street. When land is donated for the freeway (which is often the case), the landowners normally want to donate the minimum amount of land and get maximum accessibility, and TxDOT is willing to satisfy the landowner desires.
 

[lordsutch]

True, but I was more thinking of keeping the freeway at grade, and running cross streets above grade.

That would work poorly with frontage roads, as you'd have to elevate them to the cross street level, space them out wider to allow the cross street to ascend between the frontage road and the main lanes,  or overpass both the main lanes and the frontage roads and use ramps to access the frontage road. Maybe for an occasional overpass it's OK but in an urban area, you want the freeway to be the non-at-grade route.

[Marc]

2. Particularly in the Houston area, there's a design preference for running the freeway over the cross streets, rather than the reverse.

Everyone has mentioned good reasons here. I always figured it was because Houston is as flat as a pancake. That, coupled with the existence of frontage roads, it seems more logical to have the freeway crossover the cross street. For the streets that do cross over freeways, the frontage roads are either extended way out, or elevated.

With that said, there are some examples of roadways going over the freeway. Prior to widening the Katy Freeway, Grand Parkway (formerly Peek Rd.), Mason Rd., Fry Rd., and Barker-Cypress Rd. all crossed over I-10. Barker-Cypress also crosses over US 290.

[aboges26]

2. Particularly in the Houston area, there's a design preference for running the freeway over the cross streets, rather than the reverse.

Everyone has mentioned good reasons here. I always figured it was because Houston is as flat as a pancake. That, coupled with the existence of frontage roads, it seems more logical to have the freeway crossover the cross street. For the streets that do cross over freeways, the frontage roads are either extended way out, or elevated.

With that said, there are some examples of roadways going over the freeway. Prior to widening the Katy Freeway, Grand Parkway (formerly Peek Rd.), Mason Rd., Fry Rd., and Barker-Cypress Rd. all crossed over I-10. Barker-Cypress also crosses over US 290.

Here are some west Texas examples between Amarillo and Canyon:

I-27 & Lair Rd: https://www.google.com/maps/@35.0582514,-101.9194007,746m/data=!3m1!1e3

I-27 & W Rockwell Rd: https://www.google.com/maps/@35.0434991,-101.9190751,3a,75y,251.13h,79.28t/data=!3m7!1e1!3m5!1syuwBe79W0jfd0b2AGQBSyQ!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DyuwBe79W0jfd0b2AGQBSyQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D75.848022%26pitch%3D0!7i13312!8i6656

[briantroutman]

But the reason right-of-way is so narrow is because funds were very tight in the 1950s, particularly before 1956 when local governments were required to pay for most right-of-way. So they reduced the right-of-way requirement to the minimum feasible (300 feet). Both frontage roads and express lanes could not fit in that corridor width, so express lanes were on the losing end of the choice since frontage roads always take precedence in Texas.

Does anyone know of an instance (in Texas or elsewhere) where frontage roads were sacrificed in favor of transferring that right of way to the freeway?

[dfwmapper]

Unlikely in Texas. State law requires property owners to be compensated for a decrease in property value caused by loss of access to public roads, and since property with no access is basically worthless, it makes more sense for everyone involved to come to an agreement for the state to purchase a portion of the property to expand the ROW. If the property owner won't do it at a price the state considers fair, then the state uses eminent domain to force it.

[txstateends]

Does anyone know of an instance (in Texas or elsewhere) where frontage roads were sacrificed in favor of transferring that right of way to the freeway?

The closest example that might be applicable (to my knowledge) is a short portion of US 175 east of Crandall.  When the highway through there was made into a freeway in the early 1970s, the section just to the east of the city ended up with no service road for a short distance.  This section had a parallel Southern Pacific rail line up until the mid-1980s, when that track was abandoned.  Instead of shifting everything over so that there would be room for main lanes and service roads in both directions, the freeway ended up built without an EB service road between Crandall and the next exit east.  There are now plans to rectify this, since the railroad is no longer there.  Last I've heard, the rectification is still in the planning stage.

[Guysdrive780]

But the reason right-of-way is so narrow is because funds were very tight in the 1950s, particularly before 1956 when local governments were required to pay for most right-of-way. So they reduced the right-of-way requirement to the minimum feasible (300 feet). Both frontage roads and express lanes could not fit in that corridor width, so express lanes were on the losing end of the choice since frontage roads always take precedence in Texas.

Does anyone know of an instance (in Texas or elsewhere) where frontage roads were sacrificed in favor of transferring that right of way to the freeway?

yes, there are a couple places on the PGBT where a Frontage Road is gone and disappear somewhere.

[dfwmapper]

AFAIK there is nowhere along PGBT where frontage roads were removed to make room for the tolled lanes. There are places where they were never built to begin with, but that was more of a decision to not compete with the toll lanes than it was about ROW. Most of the frontage roads that do exist were built by TxDOT as part of SH 161 or SH 190 long before the main lanes were ever built by NTTA. The ones NTTA did build (e.g. in Rowlett) were usually because of the short distances between cross streets or the need to preserve access along an existing corridor.