Portions of this project are currently in design The descriptions below are based on preliminary schematics and, as a result, details may change before the project goes to construction. The first two phases of this project are being built using a design-build contract, so final plans are not available before construction starts as they typically are with a conventional bid contract. However, based on TxDOT's specifications and approved schematics for the project, the ultimate design isn't expected to differ substantially from what is described below.

TxDOT has been studying an expansion of I-35 from downtown San Antonio to the Schertz area since the mid '90s. For much of the past decade, those plans necessarily included tolled lanes due to the project's cost and funding constraints. But with the deprecation of tolling statewide in the past few years and resultant increased tax funding for highways, the toll component of this expansion has been removed, and TxDOT is now planning to expand I-35 by adding non-tolled express lanes and HOV lanes from AT&T Center Pkwy. to FM 1103. The new lanes will be elevated (double-decked) south of FM 3009 and be at-grade from there to FM 1103. Below is complete information and the latest status of this project. When all phases are completed, this stretch of I-35 should be the 14th longest road bridge in the world and 4th longest in the US according to https://en.wikipedia.org/wiki/List_of_longest_bridges.

On this page

• Background
• Project description
• Timeline
• How this project will help
  
• Schematics and renderings
  
• FAQ
• Video
  
• Other sites of interest

Background

In 1996, a Major Investment Study of the I-35 northeast corridor recommended barrier-separated express lanes as the best long-term solution for the corridor. However, acute funding shortages in the early 2000s caused this plan to be shelved.

In 2009, the Alamo Area Regional Mobility Authority (ARMA) included this corridor as a secondary phase for a local tollway system and initiated a Planning and Environmental Linkages (PEL) study in 2011, which essentially reiterated the findings of the 1996 study. The subsequent in-depth study proposed two express lanes in each direction with connectors to Loop 1604, Loop 410 Northeast, and Loop 410 South. As the plans were further fleshed-out, it was determined that the new lanes would have to be elevated along most of the route from downtown to the FM 3009 area due to right-of-way constraints. The environmental study for that project was completed and approved in 2015.

Around that time, tolling became deprecated both locally and statewide as the legislature and citizens approved new funding sources for highways. As a result, the various local planned toll projects were successively "de-tolled" as new funding sources were identified for them. Tolls were removed from the I-35 project in June 2018.

With the toll component removed, TxDOT began work redesigning the project without tolls. Additionally, recent local transportation policy changes have promoted the addition of HOV lanes to freeway expansion projects where feasible. Given the length and commuting patterns of this corridor, as well as an already impressive 10% carpooling rate, HOV lanes were determined to be a good fit and so were added to the project.

Rendering showing planned double-decking with cutaway view

Project description

This nearly $3 billion project will add non-tolled express lanes and HOV lanes on about 16 miles of I-35 from AT&T Center Pkwy. to FM 1103. The new lanes will be elevated (double-decked) south of FM 3009 and be at-grade from there to FM 1103. There will be two express lanes in each direction from AT&T Center Pkwy. to Rittiman Rd., two express lanes plus an HOV lane in each direction from Rittiman Rd. to the Bexar county line, one express lane and one HOV lane in each direction from Schertz Pkwy to FM 3009, and one new general-purpose at-grade mainlane and one HOV lane in each direction from FM 3009 to FM 1103.

The project will also build new interchanges above or near the existing interchanges to connect the new upper level lanes to Loop 410 South, Loop 410 Northeast, Loop 1604, and Pat Booker Rd., as well as an intermediate access point to and from the I-35 mainlanes at the Bexar county line, and make some incidental changes to existing roadways to accommodate the new elevated lanes and interchange ramps. The new interchanges will serve the upper levels only; the existing interchanges at those locations will remain as they are and will continue to serve the lower-level lanes of I-35.

Cross-section from AT&T Center Pkwy. to Rittiman Rd.

Cross-section from Rittiman Rd. to Bexar county line

Cross section from Bexar county line to FM 3009

Cross section from FM 3009 to FM 1103

Crossovers between the two upper levels will be provided for emergency access at three locations in the corridor: between Eisenhauer Rd. and Walzem Rd., near O'Connor Rd., and near Olympia Pkwy. (see rendering below.)

The project will also include several ramp revisions and other minor adjustments to existing roadways to accommodate the access and egress locations and columns for the new elevated lanes. Turnarounds will be added at Schertz Pkwy., Cibolo Valley Dr., and at FM 2252, and new overpasses and intersection improvements will be also included at Cibolo Valley Dr. and FM 2252.

Rendering of proposed emergency crossover near O'Connor Rd.

Timeline

Current funding constraints, as well as engineering and contracting considerations, require the project to be divided into multiple phases. Initially, funding was only available for the central segment from Loop 410 Northeast to FM 3009, including the new connectors to Loop 410 Northeast and to Loop 1604 to the west of I-35. In August 2019, the Texas Transportation Commission approved additional funding for the southern segment from Loop 410 South to Loop 410 Northeast. The remaining segments-- from FM 3009 to FM 1103, Walter St. to Loop 410 South, and the connectors for Pat Booker Rd. and for Loop 1604 east of I-35-- are currently unfunded. 

Phases 1 and 2a of this project are being built using a design-build contract, which means that TxDOT has/will select a contractor who will complete the final design of the project, build it, and then maintain it for five years. This process generally results in time and cost savings due to the ability to overlap design and construction timelines as well as increased efficiencies from a single entity managing the entire project. The remaining phases are currently planned to use the more traditional design-bid-build process.

First column for elevated lanes under construction near I-35 and Shin Oak
(Source: I-35 NEX Twitter feed)

How this project will help

This corridor experiences frequently-recurring congestion due to traffic volumes regularly exceeding the capacity of the road. Studies of the corridor in the 1990s and early 2010s determined that a significant percentage of the traffic is passing all the way through the corridor or traveling between the major interchanges, and therefore recommended barrier-separated express to segregate that traffic-- including a substantial amount of truck traffic-- from the local traffic that will remain in the existing mainlanes, thus reducing congestion there.

It is estimated that when the first phase is complete, travel time on the existing mainlanes between the Bexar county line and Loop 410 North will be cut in half from about 20 minutes to less than 10 minutes. When the entire project is complete, the travel time between FM 1103 and AT&T Center Pkwy. is estimated to be reduced from about 45 minutes to less than 20 minutes.

HOV lanes are now being added to major freeway expansion projects where feasible. The intent is to encourage carpooling and use of mass transit. Each person that opts to do so is one less vehicle on the freeway, which helps to reduce congestion and pollution for everyone. A study of this corridor showed an impressive 10% of commuters were already carpooling, a number that could increase with the provision of an HOV lane. For more information about local HOV lanes, see the HOV lanes page.

Rendering of proposed northbound double-decking near George Beach Dr.

Schematics and renderings

Click on one of the areas on the map below to open the detailed schematics for that section of the project. The base schematics are from TxDOT with my own annotations added to help clarify and explain the various elements. Each schematic will open in a new window that you can scroll and zoom.

The base schematic is the one presented to the public in August 2019. Some changes have been made since then and they've been patched over the base schematic; you may notice some slight misalignments and color differences in those locations 

On the schematic, any elevated segments colored in blue are Phase 1 (called the "base" sections in the legend.) The sections colored in green south of Loop 410 NE (schematics C and D) are Phase 2. The sections colored in green north of the Bexar county line and east of I-35 at Loop 1604/Pat Booker Rd. (schematics A and B) are Phase 3. (See phase details above.) Other improvements shown in different colors will typically be done in the corresponding phase of the adjacent elevated section.

Typical proposed double-deck section




Proposed I-35/Loop 1604 interchange
This view is looking to the west. The Forum is just off the bottom right, and IKEA now occupies the empty lot at the top left. Note that the new flyovers connect to the new upper levels of I-35; the existing cloverleaf will continue to serve the existing lower-level roadways. A change to the plans since this image was rendered is that the northbound I-35 elevated lanes exit to westbound Loop 1604 will not be a left exit as depicted here, but instead will be a righthand exit that will then go over the elevated lanes. This is shown in the next rendering below.




Proposed I-35/Loop 1604 interchange
This is an updated rendering and is looking to the east-northeast. The Forum is across the interchange and IKEA is below and slightly behind us. 




Upper level interchange at Loop 410 NE
This view is looking to the northwest. Loop 410 runs left-to-right across the top. The large building just above the center of the image is Cowboys dance hall. The elevated ramps at the top left will tie into Loop 410 at Perrin-Beitel Rd. The existing interchange will remain as-is. A change to the plans since this image was rendered is that the southbound I-35 elevated lanes exit to westbound Loop 410 will not be in the location depicted here; instead, it has been moved further north and will mirror the existing southbound I-35 exit to westbound Loop 410.




Another view of the new upper level interchange at Loop 410 NE
This view is looking north.




Loop 410 South Cutoff interchange
This view is looking south. A change to the plans since this image was rendered is that the southbound I-35 elevated lanes exit to southbound Loop 410 will cross over to the right side of Loop 410 before decending instead of merging on the left side as depicted in this image.

Video

I put together a video overview of the NEX project including a virtual flyover of Phase 1:

I-35 NEX Preview

FAQ
For questions about the HOV lanes, see the FAQ on the HOV lanes page.

• Will this project be tolled?
  No. Although earlier versions of this project proposed adding managed toll lanes, funding was secured to remove the toll component. Instead, non-tolled express lanes and HOV lanes will be added.
  
  
• Why are they building expensive elevated lanes instead of a more conventional at-grade widening?
  The existing right-of-way along most of the corridor is inadequate for a traditional widening, and because of the extensive development along the frontage roads, the cost to acquire the needed right-of-way would be more expensive-- and disruptive to the businesses and neighborhoods along the corridor-- than building the elevated lanes.
  
  
• Why aren't there more entrances and exits from the elevated lanes?
  A study of the corridor in the 1990s determined that a significant percentage of the traffic is passing all the way through the corridor or traveling between the major interchanges, a pattern that hasn't changed much today. Therefore, the intent of the new elevated lanes is to provide an express corridor for that traffic-- including a lot of truck traffic-- thus removing it from the existing mainlanes below. Since that traffic is traveling longer distances, they don't need those intermediate entrances and exits. Furthermore, additional entrance and exits would increase the traffic volumes on those elevated lanes and would also cause additional "friction" from entering/exiting traffic, both of which would engender congestion. Also, providing those additional entrances and exits would require additional right-of-way, which is limited in this corridor. This same concept is used on the I-35 elevated lanes in Austin, the Katy Freeway express lanes in Houston, the Dan Ryan express lanes in Chicago, and the New Jersey Turnpike express lanes, among others.
  
  
• The lack of entrances and exits will hinder emergency response and will trap traffic on the upper level if a crash blocks all the lanes.
  To improve access for emergency vehicles and provide an escape route for trapped traffic, emergency crossovers will be constructed at three strategic locations in the corridor: between Eisenhauer Rd. and Walzem Rd., near O'Connor Rd., and near Olympia Pkwy. This same approach has been used on other long dual-span roads that have limited or no access, most notably in Louisiana on I-10 over the Atchafalaya Swamp and on the two bridges over Lake Pontchartrain. 
  
  
• I will not use/can't access the elevated lanes, so how will it benefit me?
  Traffic that uses the elevated lanes will not be on the mainlanes below, so this will reduce traffic volumes and associated congestion there. It is estimated that when the first phase is complete, peak period travel time on the existing mainlanes between the Bexar county line and Loop 410 North will be cut in half from about 20 minutes to less than 10 minutes.
  
  

Other sites of interest

	I-35 NEX Central official project page https://www.txdot.gov/35nexcentral
	TxDOT - I-35 from Loop 410 South to FM 1103 https://www.txdot.gov/inside-txdot/get-involved/about/hearings-meetings/san-antonio/081519.html
	YouTube - I-35 Expansion Video (TxDOT) https://youtu.be/JnRfzETWzZo
	YouTube - I-35 Northeast Expansion (NEX) Central Project (TxDOT) https://https://youtube.com/watch?v=oO1P0qtCsjs