If you're just looking for information on the planned overpass at Alamo Ranch Parkway and Westwood Loop, see the Alamo Ranch Parkway at Westwood Loop project page.

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

Projects

Original TxDOT project (completed in 2017)
The original TxDOT project 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.

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. 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 theater developer, thus delaying the project. The signals finally went into operation on February 27, 2017.

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 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.

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

 

Installation of pylons on westbound ARP at Westwood Loop to prevent problematic lane changes.
These were subsequently replaced by a concrete island.
(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 (under construction)
To finally resolve the turning and associated safety issues at Westwood Loop discussed above, funding was obtained to build an overpass for westbound ARP traffic over Westwood Loop; see the Alamo Ranch Parkway at Westwood Loop project page for more information.

Westbound SH 151 ramp to northbound Loop 1604 (planned ca. 2025)
The obsolete hairpin 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.

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

• 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 traffic coming from 151 had to go somewhere onto 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.
  
  The goal of the original TxDOT project was to provide a direct connection from 151 to ARP so that traffic would no longer have to follow the access road to Culebra, turn around, and go back on the opposite access road to reach ARP, which added substantial congestion on those access roads (see traffic patterns maps above.) Also, the project was needed so that traffic going from ARP to 151 would not have to cross Loop 1604 at a the previous at-grade signalized intersection, which had to be removed in order to upgrade Loop 1604 to a freeway.
  
  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 suddenly ends at an intersection, 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 overpass is really just a long, straight exit from 151 to ARP-- it just happens to be at the end of the freeway.
  
  This is a case where drivers need to pay attention and adjust their expectations. It's a location that required an anomalous design (a situation complicated by an endangered species finding; more on that below.) Perhaps drivers would have more intuitively understood that they're exiting the freeway if the 151 access road had been extended over Loop 1604 instead of the mainlanes and ARP-bound traffic had to "exit" and use that. However, there still would have been the same issues where that access road transitioned to ARP.
  
  
• This configuration causes westbound traffic from 151 to ARP back up at Westwood Loop.
  Yes, traffic queues at that signal just as it does anywhere traffic leaves a freeway and encounters a controlled intersection such as it does on exit ramps and access roads elsewhere in the city and where freeways end and become surface roads (e.g. 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 overpass being built and it was never been claimed that the overpass would solve that. Instead, the direct overpass is an improvement over the previous circuitous route from 151 to ARP via the Loop 1604 access roads and Culebra turnaround.
  
  
• Couldn't they have extended the overpass over Westwood Loop?
  Possibly, but the state's right-of-way doesn't extend that far, and so this intersection was outside the scope of that project. In addition, it would have increased the cost of that project. They did the best they could with the funding they had at the time. Road improvements in fast growing areas with limited funding will always be an exercise in incremental improvements.
  
  That said, funding has been obtained to construct an overpass for westbound ARP over Westwood Loop; see the Alamo Ranch Parkway at Westwood Loop project page for more information
  
  
• Are there any future plans to improve the intersection of ARP and Westwood Loop?
  Yes, funding has been obtained to construct an overpass for westbound ARP over Westwood Loop; see the Alamo Ranch Parkway at Westwood Loop project page for more information
  
  
• What other improvements were considered for ARP and Westwood Loop?
  Previously-considered plans to convert the intersection to a "super street" configuration were dropped as was a previous 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 phase, thus allowing left and right turns from each (similar to the McCullough exit from southbound I-35 downtown.) It was determined that changing to a split-phase would have extended the cycle length excessively, thereby increasing congestion.
  
  
• Couldn't they have built an underpass under Loop 1604 instead of the overpass?
  That actually was the original plan, but the discovery of a federally-protected endangered spider during construction forced TxDOT to stop work and redesign the project to go over the protected habitat of that spider. The good news is that the direct connector from southbound Loop 1604 to 151 was not included in that original project, so the discovery of the spider resulted in that improvement being expedited as part of the new project.
  
  
• Why didn't they plan for the increase in traffic caused by the overpass?
  Obviously, planners knew that traffic would increase with the opening of the overpass. The challenge is something known as "latent demand" and "induced demand". These are the significant number of people who were using alternate routes to avoid the congestion and/or inconvenience of the previous 151 to ARP route, and the new development in an area that results from the improved access. While planners can do studies to attempt to estimate what that latent and induced 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, so this was the compromise. 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 did they only build the connector from southbound 1604 to 151?
  The simple answer is funding. They only had enough funding to construct one connector, and that's the one with the most traffic and most "bang for the buck". A new direct connector from westbound 151 to northbound 1604 will be built as part of an upcoming expansion of SH 151.
  
  
• Why didn't they make the connector 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 envisioned.
  
  
• 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. The new connector from 1604 enters the 151 mainlanes directly, not the access road.
  
  The reason why they didn't add an eastbound exit to Wiseman from the Loop 1604 connector is because there wasn'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 congestion. At the 1,500 foot mark, the exit to Wiseman would be quite steep and would put the end of the off-ramp much too close to the Wiseman intersection (less than 500 feet), which means drivers wanting to turn right onto Wiseman would have 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 back up onto the exit ramp during peak periods.
  
  
• Will the hairpin connector from 151 to northbound 1604 be replaced?
  TxDOT did not have enough funding in the 1604/151/ARP project to improve that ramp. However, a new direct connector for that turn will be included in a future project to widen SH 151.
  
  
• Will there be a flyover or ramp from eastbound ARP to northbound Loop 1604?
  No, there are no plans at this time for such a connector. Planners are keeping it in mind as they make other improvements in the area so as to not do anything that would interfere with one eventually being built.
  
  
• Why is there no entrance ramp 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 probhibitve.
• 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 congestionon the connector during peak periods caused by the stream of slower-moving traffic entering from Culebra trying to merge 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 soutbound Loop 1604 flyover to SH 151. To do so would actually require constructing a new flyover. If they do that, they likely would retain the existing flyover and repurpose 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.
  

TxDOT - Loop 1604 from FM 1957 to FM 471 http://www.txdot.gov/inside-txdot/projects/studies/san-antonio/loop1604-fm1957-fm471.html