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San Antonio Area Freeway System
Primer

This page last updated January 31, 2013

On this page:


Site conventions

Freeway segments: Information about the various freeways is divided by freeway segment.  Segments are based on logical divisions of the routes, or at least what I consider to be the logical divisions.  Routes with more than one segment are given directional identifiers.  For example, I-35 North is the segment of I-35 north of downtown.  Interstate 37, Interstate 410, Loop 1604, Spur 371, SH 151, and the Wurzbach and Kelly Parkways are all single-segmented.  US 90 and US 281 are technically bi-segmented, but one of their two segments runs concurrent with an Interstate, so only the non-concurrent segments are listed as the US route.  For example, US 281 South is multiplexed with I-37, so you will not find a page for US 281 South; see I-37 instead.

Travel directions: On my site, I give directions such as "northbound", "southbound", "eastbound", or "westbound"-- these indicate the specific traffic lanes along a given freeway route.  For I-10 West, since it is signed east/west but actually runs more north-south, I generally use "inbound" (i.e. toward downtown) or "outbound" instead.

Putting it together: So, what does "southbound I-35 North" mean?  The SOUTHBOUND lanes of Interstate 35 NORTH of downtown.

Route termini: On each of the pages, I discuss segments of freeway within what I consider the urbanized area of Greater San Antonio. Generally speaking, this includes the stretches of freeway that have nighttime illumination and/or one-way access roads, two hallmark urban freeway characteristics in Texas. The length listed for each segment is the length that I detail on that page. The official San Antonio Urbanized Area varies slightly from my definition.  Over time, as the city grows, I have and will extend those termini as appropriate.

Now, on with the primer...


Freeway system statistics

Below are some basic statistics about San Antonio's freeways.  All statistics are from the Federal Highway Administration (2008 data) and cover the San Antonio Urbanized Area.  The number in parenthesis is the San Antonio's rank nationally for that category.

  • Centerline miles of freeway: 233 (22)
    • Interstate highway miles: 143
    • US and State highway freeway miles: 90
  • Lane miles of freeway: 1,253 (23)
  • Daily vehicle miles driven on freeways: 19,465,000 (22)
  • Average daily traffic per freeway segment: 83,540 (50)
  • Average daily traffic per freeway lane: 15,535 (48)
  • Percent of local roads that are freeways: 4.3% (58)
  • Percent of total local daily traffic carried on freeways: 51.7% (21)

Freeway system layout

The city's freeway network was designed on the spoke-and-loop system.  Eight radials, two loops, and a spur make up the 211 mile system.  The goal of the system's planners was that no Bexar County resident would be more than 30 minutes from downtown San Antonio.  With today's traffic, the new rule is more like 30-45 minutes, but the spirit of that goal-- a comprehensive controlled-access highway network-- has been realized.  San Antonio is a classic example of a city that would come to a grinding stop without its freeways.  Most destinations require a freeway trip, even many short-distance journeys.  Only sections of the northwestern part of the city lack relatively close freeway access.

In the past, most of the city's busy freeway segments outside downtown were six lanes, but over the past couple of decades, many of them have been expanded to eight and 10 lanes.  In 2005, about nine miles of freeway were 10 lanes; today there about 30 miles.

Lane count map.  Lane counts do not include auxiliary lanes or transitional changes in lane counts.


Access roads & turnarounds

Texas uses frontage roads extensively, and San Antonio is no exception.  Locally, they're referred to as "access roads."  Only about ¼ of the freeways here don't have access roads.   These include I-10 East, I-37 South, US 281 North (between downtown and Loop 410), and about half of US 90 West.  The downtown freeways also lack access roads.  In these areas, ramp systems seen in the rest of the world are used.

Dedicated U-turn lanes are usually provided at intersections to allow traffic to turn-around and head the opposite direction on the opposite frontage road without having to traverse the signalized intersection.  In San Antonio, these are known as "turnarounds" and are so marked.

For more information on frontage roads and turnarounds, see my Texas Highways primer.
 

Turnaround

Typical San Antonio turnaround


Median barriers and fencing

Median barriers in Texas have shifted away from conventional Jersey Barrier to Constant Slope Barriers.  All new projects in the San Antonio area since the early '90s have featured that type of barrier.

Fencing atop the median barriers used to be universal on area freeways.  In the late '80s, however, median barrier fencing was phased out.  New freeway construction did not include it, and damaged sections were not replaced.  Fifteen miles of fencing was removed in 1996 on Loop 410 to accommodate conduit for TransGuide fiber optic cable atop the center barrier.  The fencing has since been removed from all of the other freeways.


Ramp metering

Like median barrier fencing, ramp meter signals are now a thing of the past in San Antonio.  The first ramp control signal was installed in May 1973 on the entrance ramp from Culebra to eastbound I-10.  By 1980, there were nine locations equipped with meter signals.  All but one of these were in the downtown area along I-10 or I-35.  The exception was the southbound US 281 entrance ramp from eastbound Basse.  San Antonio even sported an rarity in ramp metering-- a meter signal on a freeway-to-freeway ramp, specifically the southbound US 281 ramp to southbound I-35.

In addition to the meter signals, there were also two entrance ramp gates-- one on the entrance ramp from Colorado to eastbound I-10 and one on the entrance from St. Mary's to southbound I-35.  These gates were used to close the entrance ramps during the morning rush hour to help reduce congestion caused by weaving problems associated with the proximities of those entrances to other ramps.

The "Downtown Y" double-decking project (see below) during the '80s removed all of the signals and gates along
I-10 and I-35.  For a long while, the ramp meter on the Basse entrance ramp to US 281 was the last one remaining in the city, although it was rarely used.  It was upgraded in early 2005 with new equipment, but subsequently removed entirely in June 2005.

Ramp meter signal on I-10

Ramp meter signal along I-10 in 1981, probably at Woodlawn entrance to inbound I-10
 

Ramp meter map

Ramp metering map ca. 1980


Double-decked freeways (The "Downtown Y Project")

Roughly eight miles of I-10 and I-35 around downtown San Antonio are double-decked.  These freeways were rebuilt as part of the $272 million "Downtown Y" project from 1984 to 1991.  Named for the "Y" formed by I-10 and I-35 west of downtown, the project modernized 10 miles of the original four lane freeways built in the late '40s and early '50s.  Those freeways were antiquated and located in narrow canyons and on outdated viaducts.  The double-decking added elevated structures located just outside of the lower level mainlanes.  This allows two to four lanes to overhang both the lower level as well as adjacent streets, thus allowing 10 lanes to be shoehorned into virtually the same right-of-way as the original four lane freeways.  The elevated structures were built using a then-new type of construction called "segmental winged-T" bridges.  This method had two benefits: the bridges are aesthetically-pleasing, and they were able to be pre-cast off-site and trucked in and assembled, thus minimizing traffic disruption.  The segments are joined together by tensioned cables called tendons located within ducts inside the segments.  The bridges sit atop single-column support piers.

In 1995, a section of the upper level of I-10 near Fredericksburg Rd. was closed when cracks were discovered in a couple of support piers and segments.  A temporary support, similar to the ones used after an earthquake (which, coincidentally, occurred in the area a few days later) was installed and the upper level, except for the Fredericksburg Rd. entrance ramp, was reopened.  That entrance ramp, as well as the main upper level section, were eventually reinforced with strategic steel rods.  Other than this, the design has fared well, and the double-decked roads have added much needed capacity to the downtown area freeway network.  For pictures of the double-decked freeways, click here.   For a diagram on how the upper levels were built, click on the picture below.

Constructing the "Y"

Constructing the "Y"
Click on the image to see the full-sized illustration (69KB)


Speed limits

Until the repeal of the 55/65 national speed limit, all freeways in the San Antonio area were 55 mph or less, and I-35 was 55 mph all the way to FM 306 north of New Braunfels.  Most freeways inside of Loop 410 are now posted at 60 or 65 mph.  Outside of 410, speed limits are generally 65 on the Northside and 70 on the Southside.  Speed limits jump up to 70 outside of Loop 1604 on the Northside.  Loop 410 is 66 mph north of US 90 and 70 mph to the south.  Loop 1604 is generally 70 mph on its freeway segments with some 65 and 55 stretches in Live Oak and Universal City.

While the City of San Antonio still has an ordinance declaring that the minimum speed limit on freeways is 10 mph below the posted maximum speed limit, the minimum speed limit signs were removed by the late '90s. 


Left lane truck restriction

Truck ban map In 2004, the San Antonio City Council took advantage of a new state law and passed an ordinance prohibiting trucks from using the left lane of US 90 (both East and West) inside Loop 410 between 6am and 9pm Monday through Friday.  This was a trial project to determine whether similar restrictions should be implemented on other area freeways.  A before-and-after study showed an overall 10% reduction in crashes along the corridor with a 30% reduction in crashes involving trucks.  However, the restriction has not been expanded to any other freeways within the city of San Antonio.

In February 2007, the Texas Transportation Commission extended the existing left lane truck restriction in place along I-35 in the Austin area south from San Marcos to just inside Loop 1604.  A continuation of that restriction on I-35 through the city of San Antonio was subsequently investigated by no action ever taken.

   

Signs

Signage on local freeways is generally good.  However, there are a couple of areas which I feel need improvement.  Interchange Sequence Series signs (the signs that show the next three exits), which are used widely in many urban areas, are used sporadically here.  Schematic signs before major interchanges, also widely used in other cities, are conspicuously absent here.  Another peculiarity: control cities.  On radial routes, many, but not all, pull-through signs switch the inbound control city from "San Antonio" to "Downtown San Antonio" at about Loop 410.  But US 90 West and I-37 South just use "San Antonio" and I-10 West has several signs inside and outside of Loop 410 reading "San Antonio/Houston" even though signs approaching Loop 410 read "Downtown San Antonio".  Meanwhile, even when the radial control city is "Downtown San Antonio", guide signs on adjacent Loop 410 approaches just show "San Antonio".


Unbuilt freeways

The only major freeway that I know of that was part of original freeway plans and never was built was the Bandera Freeway.  This road would have filled what is now an obvious missing link in the network.  Two routes were proposed over the years for this freeway.  The first, proposed in 1964, would have started at Bandera and Huebner and followed Bandera to Evers.  It then would have paralleled Bandera slightly to the west running southeast nearly to Guadalupe before turning east, crossing I-35, following Cesar Chavez to I-37, then heading northeast to end at Commerce.  (A map of this route is here.)  The second route, proposed in 1971, would have run along Culebra from I-10 West to Loop 1604.  A "bypass connector" would have been built in conjunction with this route.  It would have arced through the near West Side connecting I-10 at Culebra to US 90 at Zarzamora, providing an inner-city bypass to the congested downtown sections of I-10 and I-35.  (Click here for a map.)

Two small connector freeways branching from McAllister Freeway were also proposed in 1964.  One would have connected 281 with I-35 roughly along St. Mary's.  The other would have upgraded San Pedro north of Loop 410 to 281.

For more information on the history of the freeway system and proposed routes, see the history page.

Looking at maps and seeing the way it was built, I also think that State Highway 16 and Spur 422, which branches off of I-35 in southwest San Antonio, was originally destined to be a freeway.  In fact, the road is officially named the Poteet-Jourdanton Freeway.  Many people (including myself) refer to it as the Poteet-Jourdanton Highway, though, although strictly technically-speaking, it should named Poteet-Jourdanton Expressway.  The road is currently a four lane divided highway with signalized intersections, but it has frontage roads along several miles.  This would have allowed the roadway to be upgraded to a freeway relatively quickly.  When the road was built, most projections saw the city expanding to the south.  Instead, San Antonio has grown northward and westward.  As a result, the relatively lightly-used Spur 422 remains mostly in its original configuration.


Metropolitan Planning Organization

The San Antonio/Bexar County Metropolitan Planning Organization (MPO) is an agency created in accordance with federal law to coordinate and distribute state and federal transportation funding for the San Antonio Urbanized Area.  This area currently includes Bexar County and parts of neighboring Comal and Guadalupe County, although there have been recent discussions about expanding the boundaries to include the New Braunfels area.  The MPO replaced the San Antonio-Bexar County Urban Transportation Study (SABCUTS).


Courtesy Patrol

The Highway Department started the Freeway Courtesy Patrol in 1968 during HemisFair to assist the high volume of tourists coming to the city for the fair.  It was disbanded after the fair, but returned in 1979.  The patrol would assist stranded motorists, clear debris from the roadways, and assist at accident scenes.  Courtesy Patrol workers provided gasoline, water, battery jump starts and tire changes, but they did not make mechanical repairs.  The patrol trucks were also equipped with fire extinguishers and traffic control equipment.  The Courtesy Patrol was discontinued in the mid 2000s due to budget issues.


Traffic congestion

Because of the extensive network of freeways, San Antonio suffers relatively low levels of overall congestion compared to other large cities, although it has increased substantially in recent years.  On average, the freeway and arterial street systems are operating slightly over capacity.  However, most Northside freeways do suffer chronic delays; Loop 410, Loop 1604, US 281, SH 151, I-10, and I-35 all have areas of moderate to severe daily congestion.  Expansion work is underway or planned for many of these roads.  The TransGuide system is also designed to manage and ease this congestion.  Rush hours are generally from 6:30-9:00 am, and 3:30-7:00 pm.


Hazardous materials route

Harzardous Cargo RouteAt one time, San Antonio was the largest metropolitan area in Texas with no hazardous cargo routing plan.  However, after a series of hazmat accidents near downtown, a plan was finally drafted.  Due to objections from the City of Castle Hills, which is bisected by Loop 410 (one of the proposed hazmat routes), the plan had to be approved by the Texas Transportation Commission, which did so in June 2001.  The map below shows the adopted hazmat routing plan.  Designated hazmat routes are marked with the "HC" sign pictured to the left above.

Hazmat route map

Vehicles with hazardous cargo are completely banned from the red sections and banned with the exception of specific local deliveries on the orange sections. All through hazmat traffic must use the green routes.
(Based on San Antonio Municipal Ordinance 94321)


The "Ice Plan"

The San Antonio area gets winter precipitation only about once or twice a year on average, usually in the form of freezing rain or sleet.  Such precipitation, of course, makes driving very hazardous.  As a result, TxDOT and the City of San Antonio have formulated a plan to manage the city's freeway system during such events.  The plan calls for TxDOT to begin de-icing bridges and overpasses using chemical agents and crushed limestone (chat rock) when such precipitation begins or is predicted.  If conditions become too dangerous, the plan calls for most of the freeway system to be closed, mostly in areas with many overpasses or elevated lanes.  To prepare for this eventuality, TxDOT has barricades pre-positioned at exit and entrance ramps to enable them to be quickly put into position by highway workers and police and has hinged signs on the freeways that, when opened, announce the road closures and direct traffic off the freeway.  Traffic is then routed to the access roads until conditions improve.


This page and all its contents are Copyright 2013 by Brian Purcell

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