Antonio Area Freeway System
last updated February 14, 2013
is San Antonio's inter-agency Advanced Transportation Management
System. When it went online in July 1995, it was the first system
of its kind in the nation and it continues to be a leader in
Intelligent Transportation Systems (ITS) technology. Now
operational on about 100 miles of freeway, the system may eventually
cover almost 300 miles of freeway in the San Antonio area.
Below is a map of
TransGuide's current coverage area.
The original 26
mile section consisting of the freeways around downtown went online on
July 26th, 1995. The sections on US 281 north of St. Mary's, Loop
410 west of I-10, and I-10 between Fulton and Wurzbach went online in
early 1999. The sections on I-10 north of Wurzbach, Loop 1604,
and Loop 410 east of I-10 went online in August 1999. The section
on I-35 between New Braunfels Ave. and Walzem went online in March
2000, and the section between Walzem and Starlight Terrace went online
in August 2000. The US 90 segment, west of Zarzamora, went online
in June 2001. The section on I-37 near Loop 410 went online in
May, 2002. The segment on I-35 north of Starlight Terrace and on
Loop 1604 west of I-10 was completed in April 2003. The section
on US 281 from Basse to Nakoma and on Loop 410 from Ingram to Culebra
were completed in 2009. Coverage of US 281 north of Nakoma to
Winding Way was completed in 2012.
TransGuide was designated as the central TxDOT unit to handle statewide
Amber Alerts and other emergency alerts.
In 2008 in
coordination with TxDOT's Austin district, ITS coverage was extended to
the entire I-35/San Antonio-Austin corridor.
In November 2009,
TransGuide upgraded their website and internal computer systems and
announced a maintenance program to clear a backlog of deferred repairs
and upgrades to field equipment.
various technologies to detect incidents and warn motorists. The
system is composed of the following major components:
divergently-routed fiber-optic rings and associated communications
- Over 2,500
inductive loop, acoustic, radar, or video-recognition (VIVDS) traffic
detectors at 220 total locations
closed-circuit, remote-controlled video cameras
- 220 mainlane
and frontage road Dynamic Message Signs (DMS)
- 246 Lane
Control Signal (LCS) systems
(currently switched-off due to maintenance funding limitations)
Traffic Operations Center (TOC)
computer system, specialized software, and related equipment
The TOC is
located in the southwest corner of the I-10/Loop 410 interchange on the
northwest side. In addition to TxDOT, the San Antonio police,
fire, and EMS dispatchers are located at the TOC, as well as
dispatchers for VIA Metropolitan Transit. This allows seamless
coordination with these agencies during major traffic incidents.
In 2009, the City of San Antonio established their own Traffic
Management Center in the TOC from which they manage the city's 1,200
How it works
The system is
designed to locate incidents within two minutes and then warn motorists
within 15 seconds. Here is how it works:
- The traffic
detectors located in each lane at ½ mile intervals measure
traffic volume and speed in 20-second rolling averages. When a
sudden or unusual change in volume or speed is detected, the system
alerts personnel at the TOC.
- Upon receiving
an alarm, operators activate the nearest camera to determine the cause
of the alarm. The operator enters information about the incident
(type of incident, lanes obstructed, and traffic data) into the system
which then searches through a database of over 30,000 scenarios and
selects a corresponding response plan based on the situation.
Police and fire dispatchers located at the TOC also use the cameras to
determine which emergency services to dispatch.
- This response
recommends what changes should be made to DMSs, LCSs, and other
equipment. These changes are presented to the operator for review
and, upon approval, the system executes all the changes within 15
seconds. TransGuide can also change the timing of traffic signals
along the access roads and major surface arteries if traffic is forced
to divert because of a freeway closure.
text-based messages alerting drivers to incidents or congestion ahead
or on an intersecting freeway. LCSs display one of the following
symbols to guide motorists into the appropriate lanes:
signals is important. Failure to do so causes increased
congestion at best and additional accidents at worst. Also, state
law requires motorists to obey them. A survey in 2007 showed
about 80% compliance with LCS and DMS messages.
late 2009, the decision was made to turn off the LCS system as a
cost-cutting measure. Maintenance on the signals had been
deferred due to financial constraints for several years and it was
determined that there simply was not sufficient funding in the
foreseeable to restore and maintain the signals. If funding is
available in the future, the system may be restored.)
years, several studies have proven TransGuide's benefits to San Antonio
motorists in the form of reduced secondary collisions, mitigated
congestion due to expedited incident clearing and 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
- 41% reduction
- 20% reduction
in response times to incidents
- Annual savings
of $1.65 million in time and fuel
- 2,600 gallon
fuel savings per major incident
- Increase in
driver compliance to posted instructions from 33% to 80%
US Department of Transportation Study, 1997)
been a leading innovator in the ITS field for over a decade. In
the future, TransGuide will continue to develop and implement new
technologies to improve traffic management. Besides continued
physical expansion of the system, other plans for TransGuide are:
- Toll system
integration: TransGuide will be fully integrated with San
Antonio's proposed tollway system.
For example, TransGuide would display travel time comparisons between
tolled and non-tolled lanes to help drivers make informed decisions on
the best route to take.
- 511 service:
TransGuide is planning to implement a local 511 telephone traffic
information service. 511 is the national standard telephone
number for such services.
Advisory Radio: These special radio stations broadcast information
about localized traffic conditions and will be especially helpful for
through trucks on the I-10 and I-35 corridors.
communication: With most major metro areas in Texas now fielding
ITS systems, it's time to start connecting these islands of information
together to improve traffic management between cities.
management: Continued improved coordination between TransGuide and
San Antonio's Emergency Operations Center will help facilitate better
response and operations during local emergencies, hurricane evacuations
and issues related to homeland security.
Frontage road DMS
Freeway mainlane DMS displaying travel time information
Lane control signals
Operations Center (inside)
Operations Center (outside)
Other sites of interest