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[i] Information AREA'S FIRST HOV LANE SET TO OPEN
The eastbound HOV lane on I-10 from Ralph Fair Rd. to La Cantera Blvd. is scheduled to open the week of September 28th.

Other San Antonio Area Roads
PROJECT INFO: Alamo Ranch Pkwy at Westwood Loop

This page last updated August 22, 2020

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Project locationLocation
Alamo Ranch Parkway (ARP) at Westwood Loop 

Status
Construction starting soon.

Description
This nearly $4 million project will construct an overpass for westbound ARP over Westwood Loop. The existing merge from SH 151 to westbound ARP between Loop 1604 and Westwood Loop will be removed. Traffic coming from SH 151 will instead continue on a new separate roadway where it will merge from two lanes to one, pass over Westwood Loop, and then merge into the existing westbound ARP approximately 1,100 feet west of Westwood Loop (i.e. in front of the Landon Ridge assisted living center) where it will become the left lane on ARP beyond the merge.

On the existing westbound ARP approaching Westwood Loop, the concrete island between the #2 and #3 lanes will be removed. All four lanes will remain, but the lane assignments will change to allow only one through lane from the second lane from the right. The two left lanes will become left-turn only and the right lane will remain right-turn only.

On ARP west of Westwood Loop, the single through lane will be joined by a lane from the turnaround, which will then merge to the right so that a single lane continues westbound into the merge from the new overpass where it will become the right lane on ARP beyond the merge location.

No changes will be made to eastbound ARP or Westwood Loop.

See the schematic at the bottom of this page for further details.

It's a common misconception that ARP in this area is SH 151 and/or is maintained by TxDOT. However, the state's responsibility ends about 400 feet east of Westwood Loop, so this intersection is technically the responsibility of Bexar County. However, the county and state agreed to build this overpass as a joint project with TxDOT designing it and managing the project to completion. Funding is from state safety funds.

How this project will help

With the completion of the SH 151-ARP connection in 2017, the westbound ARP lanes had to be segregated to prohibit left turns onto Westwood Loop for traffic coming from Loop 1604 and right turns onto Westwood Loop for traffic coming from SH 151. This caused substantially more problems than planners expected. After many reports and observations of drivers violating the turn restrictions and the resultant crashes, and attempts to mitigate the problem with bollards and a concrete island, engineers evaluated several additional options including a "split-phase" signal. However, modeling showed that a split-phase signal would have extended signal cycle times and further exacerbated delays at the intersection, and existing and future traffic volumes would have rendered most of the other options evaluated obsolete within a few years. An overpass was determined to be the best long-term solution.

For a further discussion of the history of projects in the Loop 1604/SH 151 area, see the SH 151/Alamo Ranch Parkway at Loop 1604 page.

The overpass will remove all traffic coming from SH 151 and send it over Westwood Loop before merging onto ARP. This will eliminate the need for the segregated lanes and associated turn restrictions on westbound ARP, thus allowing for all turning movements for traffic coming from Loop 1604. Removing all the SH 151 traffic will also reduce the amount of green time needed for westbound ARP, which means additional green time will be available for the other approaches; this should help to reduce congestion all around this intersection.

Timeline
Construction is expected to begin in late 2020 and should take about a year to complete.

FAQ

  • 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.

  • Why didn't they build this when they built the overpass over Loop 1604?
    This intersection is technically beyond the state's right-of-way, so it was out-of-scope for the original project, plus it would have appreciably increased the cost of the project. They did the best they could with the funding they had at the time. And frankly, traffic volumes increased more than expected and the issue with the illegal turning movements was not expected to be as problematic as it has become. It's worth keeping in mind that road improvements in fast growing areas with limited funding will always be an exercise in incremental improvements and occasional trial-and-error.


  • All they have to do is adjust the signal timing and that will solve the problem.
    It's a common belief that congestion can be solved by simply adjusting the signal timing. In some specific cases, that can be true, but at a very busy intersection like this where there has to be sufficient green time for a plethora of movements on every cycle, the signals can only be optimized so much before the laws of physics win. For example, the green time on Westwood Loop could be extended to help clear out the peak period backups that occur there, but that means the light will stay red longer for ARP, which then increases the congestion there. If the green time on ARP is then increased to ease those backups, that means the light will stay red longer for Westwood Loop and you're right back where you started. So as you can see, it's really not as easy as it sounds.

  • Why couldn't they just change the signals on westbound ARP to operate like the signals on I-35 at McCullough downtown?
    This configuration, known as a "split-phase" signal, was evaluated. However, the extra green time that would have been needed for the extra phase would have extended the red time on all the other approaches, which would have increased the congestion there.

  • They just had to add a second through lane to handle the traffic from SH 151 to westbound ARP, but the new connector from SH 151 will narrow from two lanes to one before merging with ARP. How is this an improvement?
    That's because this is not an apples-to-apples comparison. Since SH 151 traffic will fly over Westwood Loop and bypass the signal there and therefore be free-flowing, it will typically be able to move twice as much traffic over a given period than each lane at the signalized intersection. Therefore, that single lane on the overpass is roughly equivalent to two lanes at the signalized intersection. (The third through lane at the intersection services traffic coming from Loop 1604.)

  • They just added the additional through lane on westbound ARP through the Westwood Loop intersection, and now it will be taken out? That seems like it was a waste of money.
    The additional through lane (known as an auxiliary lane) was intended to be a temporary solution and provide relief until the overpass could be built, and funding for the overpass was obtained a bit faster than expected. Given traffic volumes from Loop 1604 there, only one through lane should needed. If future traffic volumes necessitate an additional through lane, the dedicated lane added from the turnaround can be used and the turnaround switched to a yield.

  • Traffic already backs-up at the signal at Lone Star Pkwy. during rush hours, so this will just exacerbate that.
    Indeed, that is a likely outcome of this. As mentioned earlier, road improvements in fast growing areas with limited funding will always be an exercise in incremental improvements, and this overpass is mainly intended to improve safety at the Westwood Loop intersection. By removing westbound traffic from SH 151 from the intersection, it will have the knock-on effect of reducing overall congestion at the intersection. So while it may make things worse downstream at Lone Star Pkwy., it should have a net overall benefit. 

  • Are there any plans for an eastbound overpass at Westwood Loop?
    Not at this time.

  • Are there any plans to extend the expressway west from Westwood Loop?
    While ARP was designed with sufficient right-of-way to allow for a narrow expressway between the existing lanes (similar to Wurzbach Parkway), there are no plans for that at this time. However, a short "stub" will be left at the western end of the new overpass for a future connection.


  • Are there any plans to extend SH 151 westward?
    A plan released in 2009 would have extended SH 151 westward as a tollway, but that was later scrapped. TxDOT currently has no plans to extend SH 151 past Loop 1604. Alamo Ranch Parkway is a county road.

Schematic
TxDOT did not have a "consumer-friendly" schematic available for this project, so yours truly created one based on the official construction plans made available by TxDOT. Note that the schematic shows the approximate locations and should not be considered to be definitive. Instead, it is intended to convey the general plan. It will open in a new window that you can scroll and zoom. 


PROJECT SCHEMATIC

Click above to see the annotated schematic for this project






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