SH 151/ALAMO RANCH PARKWAY
The new 151 to ARP overpass has generated lots of questions and complaints; answers
Antonio Area Freeway System
last updated April 10, 2015
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.
equipment will be added to Loop 1604 from Bandera to Culebra as part of
the project to upgrade that stretch to an expressway. TransGuide
cameras have been added to a couple of locations outside of the
fully-instrumented sections including at the SH 151/Loop 410
interchange and at I-10 East at Loop 1604. Additional
cameras are currently being added to Loop 1604 between NW Military and
Blanco and are planned for US 90 from Loop 1604 to SH 211.
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. TransGuide monitors the section from Loop 1604 to the Comal/Hays County line.
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.
shortages over the past decade have delayed expansion plans for the
system and resulted in substantial deferred maintenance.
Engineers estimate the maintanence funding should be $7 million a
year, but TransGuide currently only receives less than $1 million for
maintenance and roughtly $1 million for improvements.
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
detectors (mostly side-fire radar) at 150 total locations
closed-circuit, remote-controlled video cameras
- 220 mainlane
Dynamic Message Signs (DMS)
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, San Antonio and VIA transit
police dispatchers are located in the TOC. This allows seamless
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 manage the
operation of the city's more than 1,200
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.
The Texas Department of Motor Vehicles (DMV) also has their San Antonio regional office in the TransGuide building.
|Operations Center (outside)||Operations Center (inside)|
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 no plans currently to restore them.
|Freeway mainlane DMS displaying travel time information||Frontage road DMS|
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 exceeded
available resources and they were switched-off in late 2009.
However, plans have been made for a partial restoration of the
LCS system as part of future highway projects. Gantries located
at and within a mile or so of major interchanges will be upgraded and
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 80% compliance 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),
accoustic 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. 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 pasive 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.
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
- 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.
communication: With ITS systems in most of Texas' major metro areas, TxDOT plans to start connecting these islands of information
together to improve traffic management between cities. The San Antonio/Austin corridor was the first such project.
- Colocation of COSA TOC: Moving
the COSA TOC to the main TransGuide operations floor will result
in improved coordination between TransGuide and the City of San
Antonio's traffic operations center and facilitate better
response during incidents and emergencies.
- Restoration of lane control signals:
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
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