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Other San Antonio Area Roads
SH 151/Alamo Ranch Parkway/Loop 1604 area

This page last updated January 28, 2023


This page summarizes the history of various projects in the Loop 1604 - SH 151 - Alamo Ranch Parkway (ARP) - Westwood Loop area, discusses future plans, and answers frequently asked questions about this oft-maligned intersection.

The history of projects around this location illustrate the incremental method that road improvements often take and epitomizes the old addage "Don't let the perfect be the enemy of the good."

Many people just assume that either the City of San Antonio or TxDOT is responsible for all the roads in this area. However, that's not the case. TxDOT is responsible for SH 151 and Loop 1604 and their access roads. Bexar County is responsible for Alamo Ranch Parkway starting about 800 feet west of Loop 1604 including the intersection at Westwood Loop, while TxDOT is responsible to the east of that point. There are signs on Alamo Ranch Parkway that mark where Bexar County's jurisdiction begins (see below.) The City of San Antonio is not responsible for any of the roads in this immediate vicinity.

Bexar County maintenance sign on ARP

Sign (at right) marking the beginning of Bexar County jurisdiction on Alamo Ranch Parkway
(Photo by Brian Purcell)

Project History

Original TxDOT project (completed in 2017)

The original TxDOT project in 2017 constructed a flyover from southbound Loop 1604 to SH 151 and an overpass connecting SH 151 to Alamo Ranch Parkway at Westwood Loop. This overpass replaced a previous signalized intersection for eastbound traffic crossing Loop 1604 and a circuitous route along the Loop 1604 access roads for westbound traffic.

The flyover from Loop 1604 southbound to SH 151 eastbound removed all that traffic from the southbound access road and the previous signalized intersection required to cross Loop 1604 and enter SH 151. The new overpass connecting SH 151 to ARP provided a direct connection between those roadways. Prior to that, westbound traffic from 151 to ARP had to use the northbound 1604 access, take the turnaround at Culebra, then use the southbound 1604 access road to reach ARP.

The flyover and overpass allowed the previous signalized at-grade intersection on Loop 1604 at SH 151 to be removed, which was necessary in order to extend the Loop 1604 freeway to the south.

Generalized 151/1604 area traffic patterns before and after ARP overpass
Illustrates a major intent of the original state project to remove traffic from the overcrowded 1604 access roads
and 1604/Culebra intersection

Work on this project began in April 2015. The flyover from southbound Loop 1604 to SH 151 opened to traffic July 30, 2016. The ARP overpass opened on December 17, 2016.

ARP/Westwood Loop traffic signal (completed in 2017)
The intersection at ARP and Westwood Loop was originally a two-way stop (stop signs on Westwood Loop), then a four-way stop. To accommodate the expected increase in traffic, the county planned to have a traffic signal at ARP and Westwood Loop ready in time for the opening of the overpass from SH 151 in December 2016. However, the Casa Blanca theater was announced after the county had already started their planning process for the signal, so it required engineering for the signal to be paused while the county waited for the driveway and turn lane plans from the theater developer, thus delaying the signals until after the overpass opened. The signals finally went into operation on February 27, 2017. Unfortunately, there was a fatal crash at the intersection in that interim period.

ARP/Westwood Loop turn issues
Due to numerous issues with drivers making aggressive lane changes in order to make a right or left turn at Westwood Loop from westbound 151/ARP, flexible pylons were installed separating the SH 151 and Loop 1604 approach lanes. However, many drivers simply ignored these and drove over them or made illegal turns at the intersection. The pylons were replaced a few months later with a concrete island, after which some drivers continued to make illegal turns, often causing crashes.

Suggestions for a "split-phase" signal were considered but dropped after modeling showed that the increased signal cycle time required for it would substantially increase congestion on all approaches. 

New pylons on ARP at Westwood Loop 

Installation of pylons on westbound ARP at Westwood Loop to prevent problematic lane changes.
These were subsequently replaced by a concrete island (visible in the photo at the top of this page
(Photo courtesy of Josh Donat, TxDOT)

ARP/Westwood Loop additional westbound through lane project (completed in May 2019)

Due to increasing traffic congestion on westbound SH 151 at the Alamo Ranch Parkway/Westwood Loop intersection, the county built an additional lane on westbound ARP through the Westwood Loop intersection. This additional lane allowed the left lane coming from SH 151, which used to be a left turn only lane, to become a left turn/straight option lane instead, i.e. it provided two through lanes from 151 through the intersection. 

Westbound ARP overpass at Westwood Loop
To finally resolve the illegal turning and associated safety issues at Westwood Loop discussed above, funding was obtained to build an overpass for westbound ARP traffic over Westwood Loop. The overpass opened in mid October 2021. See the Alamo Ranch Parkway at Westwood Loop project page for more information.

Westbound SH 151 ramp to northbound Loop 1604 (construction starting in 2023)
The obsolete hairpin or hook entrance to northbound Loop 1604 from SH 151 will be replaced in the near future by a new direct connector as part of an expansion project on SH 151.


  • Why did they make a highway end at a traffic signal?
    It may seem like that's the case since the 151 mainlanes continue straight onto Alamo Ranch Parkway (ARP), but the point of the overpass from 151 was to provide a direct connection from 151 to ARP, and ARP is a surface street with signalized intersections, so that's just how it worked out. This situation is not unheard of and is found in many other cities.

    Since ARP lies directly ahead of the end of 151, the route must inherently go straight from 151 to ARP. Therefore, it gives the impression that the highway keeps going over 1604 and Westwood Loop and then encounters a signal, but you'll notice that the speed limit decreases to 45 mph as you approach Loop 1604, and there are large yellow "FREEWAY ENDS - SIGNAL AHEAD" signs that tell you the freeway is ending and that you are transitioning to a surface street. Therefore, the overpasses are really just a long, straight exit from 151 to ARP-- it just happens to be at the end of the freeway. Furthermore, with the addition of the overpass at Westwood Loop, traffic from SH 151 now is winnowed down to a single lane and merges onto ARP more like a typical exit ramp, which also should signal to drivers that they've left the freeway.

    This is a case where drivers need to pay attention and adjust their expectations accordingly.

    New pylons on ARP at Westwood Loop
    "Freeway ends" warning signs on westbound SH 151 approaching Alamo Ranch Parkway 

  • This configuration causes westbound traffic from 151 to back up when it reaches ARP.
    Indeed, traffic queues at the signal at Lone Star Parkway, but this happens anywhere traffic leaves a freeway and encounters a signalized intersection such as on exit ramps and access roads elsewhere in the city, and where freeways end and become surface roads (for example, southbound Loop 1604 at US 90.) As mentioned above, this is essentially an exit from 151 to ARP-- it just happens to be a straight exit at the end of 151. As such, there's no reason to expect this location wouldn't have backups like any other highly-trafficked exit from a freeway to a surface road.

    Furthermore, traffic backed up there prior to the overpasses being built and it was never claimed nor intended that the overpasses would solve that. Instead, the overpass from 151 is an improvement over the previous circuitous route from 151 to ARP via the Loop 1604 access roads and Culebra turnaround, and the Westwood Loop overpass has solved the previous problem of numerous crashes caused by illegal turning there as it was intended to do.

    The cause of the congestion is simply that the signals at Lone Star Parkway cannot provide sufficient throughput for the peak traffic volume on ARP. The wide median on ARP makes it very difficult to design an efficient signal cycle. The same problem existed on Wurzbach Parkway at NW Military Hwy.; a project that was completed there in 2022 realigned the left turns to allow for more efficient signal phasing. A similar project here-- or perhaps another alternative intersection design-- could provide relief.

  • Why didn't they extend the overpass over Westwood Loop when the overpass from 151 was built?
    There were a few reasons. First, the state's right-of-way doesn't extend that far, so this intersection was outside the scope of that project aside from some incidental work. In addition, it would have increased the cost of that project, which was already limited. And, frankly, planners just did not expect the issues that manifested there. Road improvements in fast growing areas with limited funding will always be an exercise in incremental improvements and some trial and error.

  • Why didn't they build an eastbound overpass at Westwood Loop when they built the westbound overpass?
    The westbound overpass over Westwood Loop was built specifically to solve the issue of drivers making illegal turns to Westwood Loop and causing crashes, and so it was awarded safety funding on that basis. The process to obtain funding requires demonstrating that the proposed project will solve the identified problem; an eastbound overpass in this case would not have done anything to solve the illegal/unsafe turning issue, and there wasn't a similar issue on the eastbound side, so thatís why an eastbound overpass wasnít included.

  • Are there any plans for an eastbound overpass at the intersection of ARP and Westwood Loop?
    Not at this time.

  • What other improvements were considered for ARP and Westwood Loop?
    A proposal to convert the intersection to a "superstreet" configuration was considered as was a proposal to change the westbound signals to a "split-phase" where the approaches from SH 151 and Loop 1604 would each have had their own green time, thus allowing left and right turns from each lane (similar to the McCullough exit from southbound I-35 downtown.) It was determined that changing to a split-phase would have extended the signal cycle length considerably (essentially increasing it from a four-way to a five-way intersection), thereby increasing wait times by up to 20% in all directions.

  • I heard/remember that an endangered spider caused this mess.
    Not really, and in fact, it actually made things better. Prior to the overpass, there was an earlier plan for SH 151 to pass under Loop 1604 and then intersect the southbound Loop 1604 access road at ARP. The discovery of a federally-protected endangered spider during construction forced TxDOT to stop work and redesign the project to go over the protected karst habitat of that spider. The redesign actually resulted in a few improvements:
    • First, in the original project, the east-west roadway connecting SH 151 to ARP would have crossed the southbound Loop 1604 access road at a signalized intersection, meaning traffic on one of those roadways would have a red signal to allow traffic on the other roadway to proceed. You can imagine the backups this would cause today, not only on 151 and ARP, but also on the southbound access road. Today, of course, the east-west traffic goes completely over the access road, and the only signal is for a westbound to southbound Loop 1604 left turn, which only stops eastbound traffic briefly and doesn't stop westbound traffic at all.
    • Secondly, the flyover from southbound Loop 1604 to 151 was not included in the original project. With that project, traffic on southbound Loop 1604 wanting to go to eastbound 151 would have exited onto the southbound Loop 1604 access road just south of Culebra, and then have made a left turn to go under Loop 1604 and onto SH 151 at the aforementioned signalized intersection. However, while the project was being redesigned, additional funding became available to include the flyover in the revised project.

    So actually, in the end, the spider resulted in a better outcome.
Original plans for 1604/151/ARP intersection
Original plan for SH 151/Loop 1604/Alamo Ranch Pkwy. intersection that was
cancelled due to an endangered spider being found during construction

  • Why didn't they plan for the increase in traffic caused by the overpass?
    In theory, the new overpass would only be carrying traffic that was already going from SH 151 to ARP via the convoluted access road route, so it really shouldn't have increased traffic. But improving that connection also likely triggered something known as "latent demand" or "induced demand". This when a significant number of people were using alternate routes to avoid the congestion and/or inconvenience of the previous 151 to ARP route, and after thenew overpass opened, they started using it since it was now better than their previous route (or at least perceived to be.) While planners can do studies to attempt to estimate what that latent demand might be, it's virtually impossible for anyone without a crystal ball to know for sure what that demand is until the new road opens and that traffic materializes, especially in an area like Alamo Ranch that's growing so rapidly. 

  • Why is there a signalized intersection for the ramp to southbound Loop 1604 instead of a flyover?
    There was not enough funding for a flyover for that connection, and, given the road network in this part of the city, planners estimated that there should not be a considerable amount of traffic making that turn (at least, not enough to justify the cost of a flyover), so this was the compromise. Furthermore, the peak period for traffic making that turn is in the evening when eastbound ARP/151 traffic is typically lighter. Traffic counts on that ramp since it has opened have validated planners' assumptions.

  • Why didn't they make the flyover from southbound 1604 to 151 two lanes?
    Funding for that connector was limited. Furthermore, there are not enough lanes downstream on 151 to receive two lanes from the connector plus the lanes coming from ARP plus the entrance ramp from northbound 1604. Making that connector two lanes would have resulted in a pretty significant bottleneck where it merges into 151. That said, a future upgrade to that connector is being discussed.

  • Why did they close the Wiseman exit ramp on eastbound SH 151?
    Technically, there wasn't an exit there before. Traffic coming from Loop 1604 previously was on the access road and could either enter the SH 151 mainlanes just before Wiseman or stay on the access road to Wiseman. Since the new connector from 1604 enters the 151 mainlanes directly and not the access road, it bypasses that earlier option.

  • Okay, then why didn't they add an eastbound exit to Wiseman?
    The reason why they didn't add an eastbound exit to Wiseman from the Loop 1604 flyover is because there isn't sufficient space to do so. From the end of the on-ramp coming from northbound 1604, they would need a minimum of 1,500 feet for a weave area that would be safe and minimize possible conflicts. At the 1,500 foot mark, the exit to Wiseman would be quite steep and would put the end of that off-ramp much too close to the Wiseman intersection (less than 500 feet.) This would require drivers wanting to turn right onto Wiseman to make a sharp cut across the access road, which might be difficult if more than a few vehicles were stopped at the signal and would mean that traffic would likely frequently back up onto the exit ramp.

  • Will the hairpin/hook connector from 151 to northbound 1604 be replaced?
    TxDOT did not have enough funding in the previous projects to improve that ramp. However, a new direct connector for that turn will be included in the upcoming project to widen SH 151.

  • Why didn't they build a flyover or ramp from eastbound ARP to northbound Loop 1604?
    Two reasons-- there was not enough funding or demand to build such a connector. They used the funding they did have on the most urgent need-- the southbound 1604 to eastbound 151 connector. But planners are studying it as part of a larger study for future improvements to the Loop 1604 corridor.

  • Why is there no entrance to SH 151 from Culebra?
    The decision to not include an entrance from Culebra to SH 151 was based on several factors:
    • The volume of traffic now and especially in the future needing to exit from southbound 1604 to ARP likely exceeds that of traffic needing to get from Culebra to SH 151; this made an exit for ARP a higher priority than an entrance from Culebra.
    • There is only room for one surface ramp in that area and the cost for a "braided" ramp was prohibitive.
    • There are reasonable alternatives to get to SH 151 from Culebra whereas there are very limited possibilities to get from southbound 1604 to ARP that don't add significantly to existing congestion (i.e. southbound Loop 1604 at Culebra.).
    • An entrance from Culebra onto the SH 151 connector would have resulted in significant congestion on the connector during most of the day caused by the stream of slower-moving traffic entering from Culebra trying to merge into a single lane with the stream of faster-moving traffic coming from Loop 1604, all while moving uphill to the connector. This congestion would have backed-up onto Loop 1604 as well as onto the access road and possibly into the intersection at Culebra.

    As mentioned a few bullet points above, planners are considering long-term plans that would expand the southbound Loop 1604 flyover to SH 151. To do so would actually require constructing a new flyover. If they do that, they envision retaining the existing flyover and repurposing it as a connector from the southbound Loop 1604 access road to SH 151.
  • They should fire the idiot who designed this.
    If after reading the information above you still feel that way, see this page.

Other sites of interest
TxDOT - Loop 1604 from FM 1957 to FM 471

This page and all its contents are Copyright © 2023 by Brian Purcell

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