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San Antonio Area Freeway System

This page last updated February 18, 2024

TransGuide is San Antonio's award-winning, inter-agency Advanced Transportation Management System. When it went online in July 1995, it was the most advanced system of its kind in the nation, and it continues to be a leader in Intelligent Transportation Systems (ITS) technology.

The system is now operational on about 190 miles of freeway in Bexar County and is currently under construction on about 30 additional miles of freeway. Below is a map of TransGuide's current coverage area and planned future expansions. "Full coverage" areas shown on the map are the areas with contiguous camera coverage and more extensive message signs all connected via fiber optic cable. "Auxiliary coverage" areas have more widely-spaced cameras and message signs connected via wireless communications; these can be thought-of as "TransGuide Lite" areas. Some of these areas are planned for future upgrades to full coverage.

Map of TransGuide coverage
Map legend

Map of TransGuide coverage


On this page:


In the late 1980s, Raymond Stotzer, TxDOT's San Antonio director, instructed the local district to develop an innovative ITS system that would be a model for other systems nationally. Ergo, the Texas Traffic Responsive Automated Corridor (TxTRAC) project was announced in early 1993. The system would eventually be branded as "TransGuide", and the operations center and initial 26 mile core section officially went online on July 26th, 1995. That original core section consisted of the inner loop of freeways around downtown: I‑35 from New Braunfels Ave. to Southcross Blvd., I‑10 West from I‑35 to Hildebrand Ave. (with fiber optic cable then continuing to the TransGuide building at Loop 410), I‑10 East and US 90 from Zarzamora St. to Roland Ave., and I‑37 and US 281 from St. Mary's St. to Fair Ave.

TransGuide building construction photo

TransGuide building under construction in 1994
(Photo by Brian Purcell)

Over the past two decades, the full coverage system has been gradually expanded:

In 2008, in coordination with TxDOT's Austin district, ITS coverage was extended to the entire I‑35 San Antonio-Austin corridor as the first such intercity project in the state. TransGuide is responsible for the section south of the Comal/Hays County line with Austin's ITS system taking it from there.

In 2009, TransGuide completed the first major upgrade of their computer systems and website.

In 2017, dynamic message signs and cameras were installed at strategic locations along I‑10 between San Antonio and Ozona.

Auxiliary coverage
Over the past decade or so, "auxiliary coverage" areas (my term; TxDOT is calling these "gap coverage" areas) have been added on the periphery of the primary corridors and along the Interstates into the hinterlands. These areas include cameras, dynamic message signs, and traffic monitors, but in more widely-spaced strategic standalone locations to help provide additional regional coverage at reduced cost, sort of a "TransGuide Lite."

Amber alerts
In 2006, TransGuide was designated as the central TxDOT unit to disseminate statewide Amber Alerts and other emergency alerts, and it continues that role today.

Operations center renovation
Work was completed in 2021 on a major renovation of the 25 year-old TransGuide operations center. This project renovated the main operations room and replaced the obsolete consoles, video walls, and other technology, renovated and reconfigured offices and support spaces, replaced the building's roof, and upgraded the various building utility and mechanical systems. The City of San Antonio's traffic management center, which has been located in a separate space in the TransGuide building, then moved into the main operations room to join the SAPD, VIA, and HERO dispatchers there.

TransGuide TV station
For many years, TransGuide operated a low-power UHF television station on channel 54 that broadcast a rotation of video feeds from select traffic cameras for use by local TV stations, but the signal was also available to anyone with a UHF antenna. The video was also transmitted on the City of San Antonio's cable channel during rush hours and emergencies.

In 2003, TransGuide established direct fiber-optic feeds to the local TV stations along with the capability for them to select specific camera feeds for their broadcast. Shortly thereafter, the UHF transmitter was shut down.

Model Deployment Initiative
In 1996, TransGuide was selected as one of four participants nationally for the US Department of Transportation's ITS Model Deployment Initiative (MDI). This program was developed to design, test, and pilot a variety of innovative transportation technologies. In San Antonio, those included the following:

Several of these technologies are commonplace today but were quite innovative for their time as that was before the ubiquitous Internet access, GPS, public traffic data, and Wi‑Fi that we have today. The MDI program ended in 1999.

Travel time program
In 1999, TransGuide was among the first ITS systems to display real-time estimated travel times on dynamic messages signs, which has now become commonplace nationally. Besides the explicit information it provides to drivers, one of the major benefits of showing travel times confirms to drivers that the signs and system are operational. Previously, the signs were dark unless there was an incident, and surveys indicated that many drivers interpreted the dark signs as the system being offline, which reduced confidence. After the success of travel time displays in San Antonio and a couple of other cities, the Federal Highway Administration issued a memo in 2004 that recommended travel times be the default message on DMSs.

Initially, travel times were displayed from 6:00 am to 10:00 pm. The first generation of travel times just showed the destination and a travel time range. A recent improvement has added the corresponding distance, which allows drivers unfamiliar with the route to better correlate the time to distance and therefore assess downstream conditions.


When it was first developed, the specifications called for TransGuide to be able to reliably detect incidents within two minutes, quickly verify the incident, and then be able to implement a response scenario that would update the dynamic message signs and lane control signals within 15 seconds. To accomplish these goals, TransGuide uses a variety of technologies, and the system today is composed of the following major components:

Operations Center
The TransGuide Operations Center (TOC) is located in the southwest quadrant of the I‑10/Loop 410 interchange on the Northwest Side and houses the system's central computer and communications equipment and offices for the system's managers and engineers. The heart of the building is the main operations room, which is the "mission control" style room with large video walls showing various camera and data views, and over 30 workstations for the various operators and dispatchers. In addition to TxDOT's traffic managers and HERO dispatchers, the San Antonio Police Department and VIA Metropolitan Transit also have dispatchers in the TOC. This allows seamless coordination between these agencies. The building also contains rooms for local officials and the media to use during emergencies.

In 2009, the City of San Antonio established their own Transportation and Infrastructure Management Center in the TransGuide building from which they monitor traffic on major arteries and manage the operation of the city's more than 1,400 traffic signals. Previously, COSA's center was in a separate room from TxDOT's, but after a renovation in 2021, the city and state centers were combined in order to improve coordination and efficiency between them.

From around 2010 until 2017, the regional office for the Texas Department of Motor Vehicles (which was spun-off from TxDOT in 2009) was housed in the TransGuide building. It has since moved to a location on Nacogdoches Rd.

When it was originally built, the building was inside of — and accessible only from — one of the interchange's cloverleaf ramps. The cloverleaf has since been removed, and today the building is accessible from the eastbound Loop 410 access road.

TransGuide building photo

TransGuide building
(Photo by Brian Purcell)

Operations room photo

Operations room
(Photo by Brian Purcell))

Closed-circuit cameras
TransGuide employs about 250 closed-circuit video cameras with full tilt/pan and zoom control along the city's freeway system so that traffic managers and dispatchers can view and identify incidents. These cameras are not used for traffic enforcement, and video is not recorded.

First generation camera Current generation camera

First-generation traffic camera (left) and contemporary camera (right)
The white box with antenna was part of the Model Deployment Initiative's EMS wireless communications system.
(Photos by Brian Purcell)

Traffic detectors
TransGuide originally used in-pavement induction-loop traffic detectors spaced at half-mile intervals in each lane to monitor traffic flow in order to detect congestion and associated incidents. Maintenance of those proved problematic and is no longer used, and over the past couple of decades, other traffic monitoring technologies have been developed and deployed by TransGuide at various times including transponder tags, machine vision (VIVDS) cameras, acoustic detectors, side-fire radar, and Bluetooth tracking.

Due to funding shortages in the early part of this century, maintenance and expansion of the traffic monitoring systems took a back seat to maintenance of cameras and DMSs. Today, while some side-fire radar and Bluetooth tracking are still in use, commercial GPS traffic data is the now primary source of traffic data.

Dynamic message signs
Dynamic message signs (DMSs) display text-based messages alerting drivers to incidents, congestion, or scheduled construction, providing travel times, or displaying periodic safety reminders, with humorous campaigns often going viral.

In addition to the standard mainlane DMSs, TransGuide also originally deployed frontage road DMSs at on-ramps, which was unique to San Antonio. However, as with lane control signals (see below), funding shortages have resulted in the frontage road DMSs being deactivated and, in many cases, removed, and there are currently no plans to restore them.

Future expansions and upgrades will include full-color, full-matrix DMSs, which will allow for more flexible messages including reproductions of official traffic signs and other symbols. The first such DMS in the state was installed on I‑35 near Benton City Rd. in Von Ormy.

Freeway mainlane DMS photo

Freeway mainlane DMS displaying travel time information
This specific sign was destroyed in a crash in 2017 and was not replaced.
(Photo by Brian Purcell)

Full-color full-matrix DMS photo

Full-color full-matrix DMS displaying travel time information
(Photo courtesy of TxDOT)

Frontage road DMS photo

Frontage road DMS
(Photo by Brian Purcell)

Travel time comparison signs
In conjunction with the implementation of an Advanced Traveler Information System in 2021, 17 travel time comparison signs like the one shown below were installed at various strategic "decision points" around the city. These show real-time travel times for two different routes through or around the city or downtown area so that drivers can decide which route to use. Similar signs are in use elsewhere in the state, although San Antonio's system is the largest such deployment to date. These signs differ from the travel times shown on DMSs in that they are dedicated to this purpose and show a comparison of travel times for two routes instead of single "inline" travel times for the route you are on.

Travel time comparison sign photo

Travel time comparison sign
(Photo by Brian Purcell)

Lane control signals
Lane control signals (LCSs) are devices placed over each lane to give motorists information about the downstream status (open/closed) of that lane. LCSs were an integral part of TransGuide from its inception. However, due to maintenance funding shortages in the first couple of decades of this century, the cost to maintain and operate them was deemed unsustainable, and eventually spare parts for them were no longer available. As a result, they were turned-off in late 2009 and have since been removed from some areas. With increased funding now available, there were discussions for a partial restoration of the LCS system, primarily at major interchanges, but it was determined that the benefits did not warrant the ongoing cost to maintain them. They will be removed over time as part of other construction projects.

A study in 2007 showed about an 80% compliance rate with LCS and DMS messages. (Perhaps another corollary of the old 80/20 rule.)

Lane control signals photo

Lane control signals
(Photo by Brian Purcell)

TransGuide has had a website since its launch. The original site had a very rudimentary traffic map and documentation about the TransGuide system. An upgrade in mid 1998 added an improved map that included incident and lane closure reports and DMS messages. Camera snapshots and travel times were added in 2000. As other ITS systems in Texas came online, TransGuide's site was merged into a statewide ITS site in 2010. Work is underway to add streaming video from the cameras.

TransGuide website in 1997

TransGuide website in 1997

TransGuide website in 2000

TransGuide website in 2000

Current and future expansions and upgrades

Ongoing funding shortages during the first two decades of this century delayed expansion plans for the system and resulted in a substantial backlog of deferred maintenance. This funding shortage resulted in the decision to permanently disable the system's lane control signals and frontage road dynamic message signs in 2009 as discussed above. However, recent increases in funding have allowed for renewed expansion of the system and a program to clear the backlog of deferred repairs, upgrades, and expansions. The 2021 winter storm highlighted the importance of ITS and is driving additional improvements and expansions.

The system is currently being expanded into new areas in conjunction with major freeway construction projects along Loop 1604, I‑10 East, and SH 151. Work started in late 2021 to add auxiliary coverage along Wurzbach Parkway. Additionally, cameras are being installed on I‑37 in Atascosa County and on I‑10 between Seguin and Luling, primarily for monitoring during hurricane evacuations. Future expansion of the full-coverage system is planned as part of the US 90 West expansion projects and the future phases of the I‑10/Loop 410 East interchange project.

Future expansions and upgrades will include full-color, full-matrix DMSs which will allow for more flexible messages including reproductions of official traffic signs and other symbols.

Work is currently underway to make streaming video from the cameras available on the TransGuide website.


Through the years, several studies have proven the benefits of ITS systems in the form of reduced secondary collisions, mitigated congestion (and all that entails) due to expedited incident clearing and timely driver information, and, most importantly, lives saved. Here are some statistics from one report that did a before-and-after study of the first phase of TransGuide:

(Source: Texas Transportation Institute Study, 1997)

Wrong-way driver initiative

Flashing wrong-way sign In 2011, after a series of wrong-way driver incidents culminating in the death of a San Antonio Police Department officer, a task force was established to combat the local wrong-way driver (WWD) problem. The task force included TxDOT, SAPD, the City of San Antonio Public Works department, the Bexar County Sheriff's Office, the Federal Highway Administration, and the Texas Transportation Institute. Their charge was to identify local WWD hot spots, analyze previous WWD research, investigate WWD countermeasures implemented elsewhere and determine those that could be implemented locally, and identify funding for a WWD countermeasures program.

The task force identified several countermeasures to implement including enhanced signage and pavement markings, active/illuminated signage, and detection technologies. In 2012, TxDOT began work on a pilot project to install flashing LED wrong way signs on all 29 exit ramps on US 281 north of downtown. That was followed in 2013 by installation of flashing LED wrong way signs and WWD detection radar as part of a larger expansion project on I‑35 in the Selma area. Later in 2013, WWD radar was installed on the US 281 locations, and testing of a mainlane WWD detection and warning system was completed at the Southwest Research Institute. That system detects wrong way drivers using radar, then illuminates multiple wrong way signs to alert the driver. All the ramp and mainlane WWD radar systems notify operators at TransGuide when a WWD is detected. TransGuide operators then dispatch police and activate warning messages on the DMSs along the route to alert drivers.

In addition to the above, other countermeasures that have been implemented include red reflective tape added to the wrong way signposts to increase their visibility, adjustments to the locations of the reflectors used in off-ramp pavement arrows to reduce loss due to repeated contact, and additional, repositioned, and/or larger signage where warranted.

The results of the US 281 pilot project were significant with a 29% reduction in WWD events recorded in the year after the changes were made. Since then, the system has been improved and expanded to most freeways in the area. Newer installations include multiple radar units as well as a camera. When a WWD is detected, the camera takes a picture, which is then included in the automated notifications to TransGuide and SAPD. SAPD now also announces WWD incidents over their radio with an emergency tone.

Between 2011 and 2018, the local WWD system detected and helped stop 67 wrong way drivers. TxDOT continues to refine, improve, and expand the system.

Spike strips on exit ramps
One frequent and seemingly common-sense suggestion made by the public is to install spike strips on exit ramps, such as those used in some parking lots and rental car facilities. However, this idea has been thoroughly studied and there are several reasons why they would not work in this application:

In short, although it seems like an obvious solution to the WWD problem, spike strips have too many "fatal flaws" to be a bona fide option.

HERO program

The Highway Emergency Response Operation (HERO) program, which patrols the local freeways to assist stalled motorists, clear debris, and provide traffic control at crash scenes, is operated out of TransGuide. More details on the HERO program is on the primer page.