Location
Alamo Ranch Parkway (ARP) at Westwood Loop 

Description
This nearly $4 million project has constructed an overpass for westbound ARP over Westwood Loop and the existing merge from SH 151 to westbound ARP between Loop 1604 and Westwood Loop has been removed. Traffic coming from SH 151 instead now continues on a new separate roadway where it merges from two lanes to one, passes over Westwood Loop, and then merges into the existing westbound ARP approximately 1,100 feet west of Westwood Loop where it becomes the left lane on ARP beyond the merge.

On the westbound access road from Loop 1604 approaching Westwood Loop, the previous concrete island between the #2 and #3 lanes has been remove and the lane assignments  adjusted.

Simplified line schematic showing lane configuration for westbound traffic

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, and this location is not in the City of San Antonio, 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 overpass in 2017, the westbound lanes had to be segregated to prohibit left turns onto Westwood Loop for traffic coming from Loop 1604 and to prohibit 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 and a "super street" configuration. However, modeling showed that a split-phase signal would have lengthened 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.

The overpass removes all traffic coming from SH 151 and sends it over Westwood Loop before merging onto ARP. This eliminates the need for the segregated lanes and associated turn restrictions on westbound ARP at Westwood Loop, thus allowing for all turning movements for traffic coming from Loop 1604. Removing all the SH 151 traffic also reduces the amount of green time needed for the westbound ARP signal (for traffic coming from Loop 1604), which means additional green time is available for the other approaches.

The drawback to this change is that traffic headed westbound on SH 151 no longer can no longer directly access Westwood Loop. Those drivers should exit prior to Loop 1604 and access Westwood Loop via the Loop 1604 access roads, or they can use the turnaround at Lone Star Parkway.

• This project did nothing to alleviate the evening rush hour congestion on westbound 151 exiting to ARP.
  This project was not intended to alleviate that congestion (not all road projects are to address congestion.) Instead, this project was a safety project designed to address the specific previous problems at Westwood Loop of people turning illegally and causing lots of crashes. The turning restrictions that were being violated were necessitated by the conflicts caused by the previously combined traffic flows there from 151 and 1604. Separating the 151 traffic onto the overpass eliminated that conflict and allowed those turning restrictions to be removed.
  
  
• Traffic already backed-up at the signal at Lone Star Pkwy. before this project, and this had just exacerbated that.
  Yes, it's true that traffic did back up there before, which means it was going to back up there anyway without the overpass, so this project didn't cause that. Now, instead of that westbound traffic backing up at two intersections like it did before, it only backs up at the one (Lone Star.) In any case, this overpass was intended to address the specific previous safety issue at Westwood Loop of people turning illegally and causing lots of crashes; it was not intended nor designed for congestion relief. While it may seem like it's making things worse downstream at Lone Star Pkwy., it's really not since it's not introducing any new traffic that wouldn't have already been there anyway, and it is still having a net overall benefit by improving safety at Westwood Loop. It also eliminates a signal for westbound 151 traffic, which is certainly beneficial during off-peak periods, and it reduces westbound traffic through the Westwood Loop intersection, which can give some "breathing room" for the signals to better handle the remaining traffic.
  
  
• 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. After completion of that project, traffic volumes increased more than expected, and the issue with the illegal turning movements was not expected to be as problematic as it became. 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 had to do is adjust the signal timing and that will solve the problem.
  It's a common belief that congestion could have been 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 by about 20%, which would have increased the congestion there. (The traffic volumes at the I-35/McCullough intersection are low enough that the split-phase does not cause excessive delays.)
  
  
• They had just added a second through lane to handle the traffic from SH 151 to westbound ARP, but the new connector from SH 151 narrows 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 now flies over Westwood Loop and bypassed the signal there, that single lane 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 the two previous lanes from SH 151 at the signalized intersection. (The third through lane at the intersection serviced traffic coming from Loop 1604.)
  
  
• They had just added the additional through lane on westbound ARP through the Westwood Loop intersection, and now it's been 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 the traffic volumes coming from Loop 1604 there, only one through lane should be needed at that location. 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. However, that would likely need be done in conjunction with an expansion of ARP further west.
  
  
• 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" was built at the western end of the new overpass for a future continuation of the westbound lanes.
  
  
• 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 currently 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