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San Antonio Area Freeway System
I‑35 Northeast Expansion (NEX) Program

This page last updated June 12, 2024

Engineer

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 program are being built using a design-build contract, so final plans were not available before construction started as they typically are with a conventional bid contract. However, based on TxDOT's specifications and approved schematics, the ultimate design isn't expected to differ substantially from what is described below.

Project location mapTxDOT 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 increased funding for state highways and the deprecation of tolling, 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 Frost Bank Center Dr. 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 about this project and the latest status.

Bridge length rankings
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 Wikipedia.



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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 voters 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 therefore were added to the project.

I-35 NEX cutaway view

Rendering showing planned double-decking with cutaway view
(Courtesy of TxDOT)


Project description

This $3.2 billion project will add non-tolled express lanes and HOV lanes on about 16 miles of I‑35 from Frost Bank Center Dr. to FM 1103. The new lanes will be elevated (double-decked) south of FM 3009 and will be at-grade from there to FM 1103. There will be two express lanes in each direction from Frost Bank Center Dr. 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 the county line to FM 3009, and one new at-grade general-purpose 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 what will become the lower-level lanes of I‑35.


Cross-section from Frost Bank Center Dr. to Rittiman Rd.

Cross-section

Cross-section from Rittiman Rd. to Bexar county line

Cross-section

Cross section from Bexar county line to FM 3009

Cross-section

Cross section from FM 3009 to FM 1103

Cross-section

NOTE: In the cross-sections above, the number of access road lanes varies depending on location. Diagrams are for illustrative purposes only and are not to scale.


Unlike the double-decked freeways downtown, the upper levels on this project will be express lanes, meaning there will be limited entrances and exits along their length. The intent for the new lanes is to provide an express facility for longer-distance through traffic in the corridor, but this will also benefit the lower-level by removing much of that long distance traffic from those lanes.

In addition to the north end (FM 3009 area) and south end (Frost Bank Center Dr. area), motorists will also be able to enter or leave the elevated lanes at the following locations:

I-35 NEX access map

Elevated lanes access points

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 crossover

Rendering of proposed emergency crossover near O'Connor Rd.
(Courtesy of TxDOT)


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 half of the southern segment stretching from Loop 410 South to Loop 410 Northeast. The remaining segments — from FM 3009 to FM 1103, Walters 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 selected 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.

I-35 NEX phases map

I‑35 NEX project phases

PHASE 1 (Central segment): Loop 410 Northeast to Bexar county line

This phase will include the following:


PHASE 2a (South segment Project 1): Loop 410 South to Loop 410 Northeast

This phase will include the following:


PHASE 2b (South segment Project 2): Loop 410 South from I-35 to FM 78

This phase will include the following:


PHASE 2c (South segment Project 3): Walters St. to Loop 410 South

This phase will include the following:


PHASE 3 (North segment): Bexar county line to north of FM 1103.; Pat Booker Rd./Loop 1604 East interchange

This phase will include the following:

Column construction photo

First column for elevated lanes under construction in January 2023 near I‑35 and Shin Oak



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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 is 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 Frost Bank Center Dr. 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 in San Antonio 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 I-35 NEX

Rendering of proposed northbound double-decking near George Beach Dr.
(Courtesy of TxDOT)


Schematics and renderings

Click on one of the letters 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 I've patched them 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.

Click on one of the letters on the image above to open the detailed schematic for that section

Below are several renderings of what the finished project might look like. Note that since this project is still in design, these are conceptual and the exact final project may vary from these. Renderings are framegrabs from TxDOT's I‑35 Expansion Video and I‑35 Northeast Expansion (NEX) Central Project video (Links in the "Other sites of interest" section below.)

Artist rendering

Typical proposed double-deck section

Artist rendering

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 right-hand exit that will then go over the elevated lanes. This is shown in the next rendering below.

Artist rendering

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.

Artist rendering

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.

Artist rendering

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

Artist rendering

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 descending 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


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/projects/hearings-meetings/san-antonio/archive/081519.html
YouTube - I‑35 Expansion Video (TxDOT)
https://www.youtube.com/watch?v=JnRfzETWzZo
YouTube - I‑35 Northeast Expansion (NEX) Central Project (TxDOT)
https://www.youtube.com/watch?v=oO1P0qtCsjs