Antonio Area Freeway System
last updated June 3, 2019
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 over 100 miles of freeway, the system is currently being expanded to about 50 more miles.
is a map of
TransGuide's current coverage area and planned future
mile section consisting of the freeways around downtown went online on
July 26th, 1995. The sections on US 281 north of St. Mary's St., Loop
410 west of I-10, and I-10 between Fulton Ave. and Wurzbach Rf. went
early 1999. The sections on I-10 from Wurzbach Rd. to Camp Bullis
Blvd., 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 Rd. went online in March
2000, and the section between Walzem Rd. and Starlight Terrace went
in August 2000. The US 90 segment, west of Zarzamora St., went online
in June 2001. The section on I-37 near Loop 410 went online in
May, 2002. The segment on I-35 from Starlight Terrace to Loop 1604 and
Loop 1604 from I-10 to Bandera Rd. was completed in April 2003. The
on US 281 from Basse Rd. to Nakoma Dr. and on Loop 410 from Ingram Rd.
to Culebra Rd.
were completed in 2009. Coverage of US 281 from Nakoma Dr. to
Winding Way was completed in 2012. The section on Loop 1604 from Braun
to Culebra Rd. 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 south of the Comal/Hays County line.
2017, DMSs and cameras were installed at strategic locations along I-10
Antonio and Ozona.
shortages over the past two decades have delayed expansion plans for
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 well less than that for many
funding shortage resulted in the decision to permanently turn-off
the system's lane control signals and frontage road dynamic message
signs (DMSs) in 2009. In
TransGuide upgraded their website and internal computer systems.
Recent increases in funding have allowed for renewed expansion of the system and a program to clear the backlog of deferred repairs
and upgrades to field equipment. Engineers
are also hoping to soon revive lane control signals at
Current and future expansions
system is currently being expanded into new areas in conjunction with
major freeway construction projects along US 281 north of
Loop 1604, I-10 from Camp Bullis Rd. to Leon Springs, Loop 410 from
Rd. to US 90 West, Loop 1604 from SH 151 to US 90 West, and I-10 East
from Loop 410 to Loop 1604. Additionally, work will begin in mid 2019
on standalone expansions of the system on Loop 1604 between
I-10 and I-35, and US 281 from Nakoma Dr. to Loop 1604.
project to construct an Advanced Traveler Information System (ATIS) began
mid 2018. This project includes 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
the southern and eastern approaches to the city. The purpose of this
system will be to
give motorists information on the fastest route to take through (or
around) the city.
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)
travel time comparison (TTC) signs (coming
traffic operations center (TOC)
computer system, specialized software, and related equipment
Traffic management 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 TMC.
coordination with these agencies during major traffic incidents.
2009, the City of San Antonio established their own traffic 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. Currently, COSA's TMC is separate from TxDOT's,
but work is underway to combine the two in order to improve
coordination and efficiency between them.
Dynamic message signs
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 currently no
plans to restore them.
mainlane DMS displaying travel time information
Lane control signals
control signals (LCSs) placed over each lane give motorists information
about the downstream status of that lane. LCSs have been a part
of TransGuide since its inception; however, due to severe maintenance
funding shortages, the cost to maintain and operate them was deemed
unsustainable and they were switched-off in late 2009 and have since
been removed from some areas. However,
with recent funding increases, plans are in the works for a partial
restoration of the
LCS system, primarily at major interchanges.
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 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 traffic managers can view and identify
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 major "decision
around the city. 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 single "inline"
times for the route 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 construct an Advanced Traveler Information System (ATIS)
began mid 2018. This project includes 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 southern and eastern approaches to the
city. The purpose of this system will be to give motorists information
on the fastest route to take through (or around) the city. 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 TMC: Moving
the COSA TMC 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 first reported by phone, TransGuide is useful in determining the
precise location of the incident as telephoned reports are often vague
or inaccurate. 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 helps improve response times and results in incidents being cleared 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 shown during
periods without congestion may seem pointless to those who travel the
road often, they do serve the purpose of reassuring drivers that the
route ahead is clear and that the system is online. (Studies have shown
that when DMS signs are blank, many drivers assume the system is not
operating.) When the road
is congested and travel times increase correspondingly, motorists can
use the travel times shown to 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?
Much of the funding
for TransGuide comes from funding sources dedicated to
Intelligent Transportation Systems (ITS). As a result, that
money cannot be used for anything other than ITS
projects. If TransGuide didn't get that money, some other city's
traffic management system would. Furthermore, the amount of money spent
on ITS projects is substantially less per mile than roadway expansions,
so eliminating ITS funding would not result in many new highway lanes.
Compared to roadway expansions, ITS has been shown to result in a more
substantial and longer-lasting return-on-investment. Regardless, it is
well-understood now that there is a point when you
can no longer just build your way out of congestion. Instead, you have
to manage what you have, which is the intent of ITS systems.
sites of interest