Antonio Area Freeway System
last updated June 8, 2018
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 a little over 100 miles of freeway, the system may
cover almost 300 miles of freeway in the San Antonio area.
is a map of
TransGuide's current coverage area and planned future expansions.
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. The section on Loop 1604 from Braun
to Culebra went online in mid 2016.
cameras have also been installed at several locations outside of the
fully-instrumented sections including at SH 151 and Loop 410,
East and Loop 1604. I-35 South and Loop 1604, and several locations on
Loop 410 South between I-35 and I-37, Loop 1604 North between I-10 and
US 281, and US 90 between Loop 1604 and SH 211.
TransGuide was designated as the central TxDOT unit to handle statewide
Amber/Silver Alerts and other emergency alerts.
coordination with TxDOT's Austin district, ITS coverage was extended to
the entire I-35/San Antonio-Austin corridor. TransGuide monitors
the section from the Bexar County line to the Comal/Hays County line.
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.
shortages over the past decade have delayed expansion plans for the
system and resulted in a substantial backlog deferred maintenance.
Engineers estimate the maintenance funding should be $7 million a
year, but TransGuide has been receiving less than $1 million for
maintenance and roughly $1 million for improvements. This
funding shortage resulted in officials deciding to permanently turn-off
the system's lane control signals and frontage road dynamic message signs (DMSs) in 2009.
are hoping to soon revive the lane control signals at major
2017, DMSs were installed along I-10 between San
Antonio and Ozona.
Current and future expansions
system is currently being expanded into new areas in conjunction with
major freeway construction projects. These are along US 281 north of
Loop 1604, I-10 from Camp Bullis to Leon Springs, Loop 410 from Ingram
to US 90 West, and Loop 1604 from SH 151 to US 90 West. There are plans
to expand the system in 2019 to existing sections of Loop 1604 between
I-10 and I-35 and US 281 from Nakoma to Loop 1604 as well as in
conjunction with the further expansion of US 281 north of Stone Oak.
project to construct an Advanced Traveler Information System (ATIS)
will begin in mid 2018. This project will include the installation of 17 travel time comparison (TTC) signs at major decision points
citywide, 40 additional
Bluetooth sensors to improve travel time calculations, and new DMSs and cameras on
the South and East sides of town. The purpose of this system will be to
give motorists information on the fastest route to take through (or
around) the city. More details on this system are below.
various technologies to detect incidents and warn motorists. The
system is composed of the following major components:
divergently-routed fiber-optic rings, wireless transmitters/receivers,
and associated communications
detectors (mostly side-fire radar and Bluetooth sensors) at ~200 total
closed-circuit, remote-controlled video cameras
mainlane dynamic message signs (DMS)
- 17 travel time comparison (TTC) signs (coming
- Three-story traffic operations center (TOC)
computer system, specialized software, and related equipment
Traffic operations center
located in the southwest corner of the I-10/Loop 410 interchange on the
Northwest Side. In addition to TxDOT, the San Antonio Police Department
and VIA Metropolitan Transit have dispatchers co-located in the TOC.
coordination with these agencies during major traffic incidents.
2009, the City of San Antonio established their own TOC 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. Currently, COSA's TOC is separate from TxDOT's,
but plans are in the works to combine the two in order to improve
coordination between them.
Dynamic message signs
|Operations center (outside)
||Operations center (inside)
text-based messages alerting drivers to incidents or congestion ahead
or on an intersecting freeway. The TransGuide system employs both
mainlane and frontage road (entrance ramp) DMSs; however, due to
maintenance funding shortages, frontage road DMSs have been deactivated
and there are no plans currently to restore them.
mainlane DMS displaying travel time information
Lane control signals
control signals (LCSs) placed over each lane give motorists information
about the status of that lane downstream. LCSs have been a part
of TransGuide since it began; however, due to severe maintenance
funding shortages, the cost to maintain and operate them was
unsustainable and they were switched-off in late 2009 and have since
been removed from some areas. However,
plans are in the works for a partial restoration of the
LCS system, primarily at major interchanges.
Lane control signals
LCSs display one of the following
symbols to guide motorists into the appropriate lanes:
law requires motorists to obey LCS signals. A survey in 2007 showed
about an 80% compliance rate with LCS and DMS messages.
originally used conventional in-pavement induction-loop traffic
detectors spaced at half-mile intervals in each lane to monitor traffic
flow in order to detect slow-downs and associated incidents. Over
the past decade or so, other traffic monitoring technologies have been
developed including transponder tags, video/machine vision (VIVDS),
acoustic detectors, side-fire radar, and Bluetooth tracking, all of
which have been implemented at various times by TransGuide. Today,
side-fire radar is the main technology employed along with
some Bluetooth tracking in the I-35 corridor (currently being expanded
citywide.) However, due to
funding shortages, maintenance of the traffic sensors has been a lower
priority than cameras and DMSs, so most corridors no longer have
comprehensive passive traffic monitoring. If funding is increased,
restoration of this capability is a priority. In the meantime,
the remaining detectors are used along with 911 reports and cameras to
locate congestion and incidents.
employs more than 200 closed-circuit video cameras along the city's
freeway system so that officials can view and identify incidents. These
cameras offer full pan/tilt and zoom control. These cameras are not
used for traffic enforcement and video is not recorded.
First-generation closed-circuit camera
Travel time comparison signs
In conjunction with the implementation of an Advanced Traveler
Information System (see below), 17 travel time comparison signs like
the one shown below will be installed at various "decision points"
around the freeway system. These will show the travel times through the
city or section of the city on two different routes so that drivers can
decide which route to use. Similar signs are in use elsewhere in the
state. These signs differ from the travel times currently shown on
existing DMSs in that they are dedicated to this purpose and show
comparisons of travel times on two routes instead of "inline" travel
times for the freeway you are on.
Travel time comparison sign in Temple
years, several studies have proven the benefits of ITS systems 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
in response times to incidents
of $1.65 million in time and fuel
fuel savings per major incident
driver compliance to posted instructions from 33% to 80%
US Department of Transportation Study, 1997)
been a leading innovator in the ITS field since its inception. In
the future, TransGuide will continue to develop and implement new
technologies to improve traffic management. Besides continued
physical expansion of the system (described at the top of this page), other plans for TransGuide are:
Traveler Information System: A project to install 17
Travel Time Comparison (TTC) signs at major decision points citywide
will begin in mid 2018. This project will also add 40 additional
Bluetooth sensors to improve travel time calculations and new DMSs and cameras on
the South and East sides of town. This
system will give motorists information so they can make
informed decisions on
the best route to take through
(or around) the city.
communication: With ITS systems in most of Texas' major metro
areas, TxDOT has started connecting these islands of information
together to improve traffic management between cities. The San
Antonio/Austin corridor was the first such project.
of COSA TOC: Moving
the COSA TOC to the main TransGuide operations floor will result
in improved coordination between TransGuide and the City of
Antonio's traffic operations center and facilitate better
response during incidents and emergencies. This project is planned for 2019.
- Restoration of lane control
The LCS system was switched-off in late 2009 due to a lack of
maintenance funding. Over the next few years, some LCS gantries
will resume operation, mainly in the vicinity of major interchanges.
- Restoration of traffic sensors:
Like the LCS system, funding shortages have resulted in the loss of
numerous traffic sensor locations. This has reduced the ability
of TransGuide to monitor traffic flow along many corridors. If
funding levels improve, restoration of this equipment is a high
are answers to some frequently-asked questions about TransGuide:
the point of TransGuide? All it ever tells me about is congestion that
I see everyday and already know about.
it's true that many TransGuide messages are about areas of chronic or
recurring congestion that are familiar and well-known to commuters
along those routes. However, these congestion reports are useful to
people who are not familiar with that road (e.g. truckers and tourists
passing through, local residents who don't usually travel that route,
etc.) and are also useful as reminders to regulars to be cautious as
they approach the congestion. Studies have shown that these warnings
improve the traffic flow and safety in the areas where they are used.
TransGuide's original intent, and the area where it really provides
benefits, is reporting on incidents that cause unusual or severe
congestion, and providing those reports in a timely manner to allow
motorists to take alternate routes. Also, TransGuide can often detect
such incidents before they are even reported by phone and, even when an
accident is reported by phone, TransGuide is useful in determining the
precise location of the incident as telephoned reports are often vague
or inaccurate in this regard. Furthermore, TransGuide's operators can
determine the full extent of the incident to ensure that the proper
assistance is dispatched immediately. These factors combine to mean
that TransGuide saves lives and helps clear incidents faster.
the point of the travel times on TransGuide signs? I know how long it
takes to get where I'm going.
travel times shown on TransGuide signs are computed every minute based
on real-time traffic conditions. While the times they show during
periods without congestion may seem pointless to those who travel the
road often, they do serve the purpose of providing regular travelers of
the road with a "baseline" travel time for a route. Then, when the road
is congested and travel times increase correspondingly, travelers
familiar with that "baseline" travel time can judge the severity of the
downstream congestion and determine whether or not to use an alternate
still think TransGuide is a waste of money. Why don't they use the
money spent on TransGuide building new highway lanes?
for TransGuide comes from funding allotments reserved only for
Intelligent Transportation Systems (ITS). As a result, the money that's
used for TransGuide cannot be used for anything other than ITS
projects. If TransGuide didn't get that money, some other city's
traffic management system would. Besides, there comes a point when you
can no longer just build your way out of congestion. Instead, you
to manage what you have. That's the function of TransGuide, not to
mention the previously-mentioned benefits to safety. All-in-all, ITS
systems provide a high return-on-investment.
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