On this page:

• Site conventions and coverage
• Freeway system statistics
• Freeway system layout
• Access roads and turnarounds
• Median barriers and fencing
• Ramp metering
• Double-decked freeways
• Speed limits
• Left lane truck restriction
• Signs
• Unbuilt/cancelled freeways
• Metropolitan Planning Organization
• HERO/Courtesy Patrol
• Traffic congestion
• Hazardous materials route
• The "Ice Plan"

Site conventions and coverage

Site coverage: The area covered by the "San Antonio freeway system" section of this site is generally the urban and suburban freeways. In that past, that was fairly easily discernible by one-way access roads and continuous streetlighting, but over the years, the lines have become more blurred as TxDOT has extended one-way access roads into the surrounding hinterland and streetlighting has become a bit more inconsistent. So I use a completely subjective determination on where I draw the line. As of right now, here are the boundaries of the freeways I cover:

• I-10 East: Pfeil Rd.
• I-10 West: Ralph Fair Rd.
• I-35 North: FM 482/FM 2252
• I-35 South: Loop 1604
• I-37: US 181
• US 90 West: Loop 1604
• US 281 North: Sonterra Pkwy. (will be extended to the Comal county line upon completion of the freeway expansion)

These will change over time as the city grows.

Loop 1604 is covered along its freeway section (currently US 90 West around to FM 78.) Loop  410, SH 151, General Hudnell Drive/Spur 371, and Wurzbach Parkway are covered in their entirety.

Coverage of major projects on I-10 west toward Boerne, I-35 north toward New Braunfels, and Loop 1604 on the South Side is included in the "Other San Antonio Roads" section.

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 seem to me to be the logical divisions. Routes with more than one segment are given directional identifiers based on their position relative to downtown. For example, I-35 North is the segment of I-35 north of downtown. Interstate 37, Spur 371, SH 151, and the Wurzbach and Kelly Parkways are all single-segmented. Loops 410 and 1604 are also single-segmented for the purposes of this site, although they are divided into north, south, east, and west segments for addressing and general referral. US 90 and US 281 are technically two-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 runs concurrent with I-37, so you will not find a page for US 281 South; see I-37 instead.

Travel directions: On this site, directions such as "northbound", "southbound", "eastbound", or "westbound" are used-- 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, "inbound" (i.e. toward downtown) or "outbound" are sometimes used instead if needed to avoid confusion.

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

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 (2017 data) and cover the San Antonio Urbanized Area. The number in parenthesis is the San Antonio's rank nationally for that category for the top 100 urbanized areas.

• Centerline miles of freeway: 258 (21)
  • Interstate highway miles: 142
  • US and State highway freeway miles: 86
• Percent of local roads that are freeways: 3.2%
• Daily vehicle miles driven on freeways: 24,890,000 (21)
• Percent of total local daily traffic carried on freeways: 50.9% (10)

Freeway system layout

The city's freeway network was designed on the spoke-and-loop system. Eight radials, two loops, a spur, and a crosstown parkway make up the system. The goal of the system's planners in the 1950s was that no Bexar County resident would be more than 30 minutes from downtown San Antonio. With today's traffic and overall growth of the city, 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. Many destinations require a freeway trip, including many short-distance journeys. Only a swath of the northwestern part of the city lacks relatively close freeway access.

Lane counts
Lane counts on this site include the total lanes in both directions. Thus, a freeway with three lanes in each direction is labeled as a six-lane freeway. Counts are for general-purpose through lanes; auxiliary lanes of less than a mile are not included nor are HOV lanes.

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 are roughly 30 miles, with more planned.

Lane count map
Lane counts do not include short (< 1 mile) auxiliary or transition lanes or HOV lanes.

Access roads & turnarounds

Texas uses frontage roads extensively, and San Antonio is no exception. Locally, they're traditionally referred to as "access roads." Only about one-fourth of the freeways here don't have access roads. These include sizable sections of 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, interchange types used 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 generally signed as such.

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

Typical San Antonio turnaround

Median barriers and fencing

Median barriers in Texas have shifted away from conventional Jersey Barrier (sometimes called "K-rails") to Constant Slope Barriers. All new projects in the San Antonio area since the early '90s have featured the newer type of barrier.

Fencing/glare screens atop the median barriers used to be universal on area freeways. Due to increasing maintenance costs, median barrier fencing was phased out from new projects starting in the late '80s, 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, and the fencing was removed from all of the other local freeways circa 2000.

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 had a 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 (both of these ramps no longer exist.) These gates were used to close the entrance ramps during the morning rush hour to help reduce congestion caused by traffic influx and 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 metering map ca. 1980
(Source: San Antonio-Bexar County Urban Transportation Study)

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 1983 to 1994. Named for the "Y" formed by I-10 and I-35 west of downtown, the project improved 10 miles of the seminal four-lane freeway system built in the late '40s and early '50s. Besides being obsolete, those freeways had suffered from chronic congestion almost since they had opened. Earlier proposals to relieve the congestion there by constructing a bypass route on the near West Side were eventually scuttled. 

About six miles of the original freeway was located below grade and in a narrow right-of-way that made a conventional widening prohibitively expensive. The double-decking added elevated structures on a single row of piers located just to the outside of the lower level but within the existing right-of-way. This allowed the upper level to overhang the lower level, thus allowing the additional lanes to be shoehorned into the original right-of-way.

The elevated structures were built using a then-new type of construction called "segmental winged-T" bridges. Besides being aesthetically-pleasing, this method had the major technical benefit of allowing the bridge segments to be cast off-site and then trucked in and assembled in-place, thus expediting construction and minimizing traffic disruption. Segments were lifted onto a special support truss and joined together with epoxy. Then tensioned cables called tendons located within ducts inside the segments were tightened to hold the structure together. It was likened to a suspension bridge but with the cables inside the bridge.

An observant motorist driving on the lower levels may notice a difference in the piers used on each side of the road. The original design was modified midway through the project to allow for improvements to the bridge segments that made the casting process easier and reduced costs. This new design increased the width of the bridge "spines" and, thus, required a wider pier to support it.

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 to support damaged bridges 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 provided much needed capacity to the downtown area freeway network. For photos of the double-decked freeways, click here. For a diagram on how the upper levels were built, click on the image below.

Constructing the "Y"
Click on the image to see the full-sized illustration
(Source: San Antonio Light)

In 2018, TxDOT announced plans to double-deck 15 miles of I-35 on the northeast side. When completed, this will likely be the longest section of double-decked freeway in the country and possibly the world.

Speed limits

Prior to 1987, the national speed limit was 55 mph, and all freeways in San Antonio were posted at 55 mph with the downtown freeways posted at 50. In 1987, the federal government permitted states to increase the speed limit to 65 mph on rural Interstates. In San Antonio, this applied to I-10 West north of Loop 1604 and to the other Interstates outside Loop 410 with the exception of I-35 North, which was posted at 55 mph all the way to FM 306 north of New Braunfels. The national speed limit was completely repealed in 1995.

Today, most freeways inside of Loop 410 are posted at 60 or 65 mph. Outside of 410, speed limits are generally 65 on the North Side and 70 on the South Side. Speed limits jump up to 70 outside of Loop 1604 on the North Side. Loop 410 is 65 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, minimum speed limit signs were removed during the mid and late '90s. 

Left lane truck restriction

In 2004, the San Antonio City Council 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 but no action ever taken.

Signs

Signage on local freeways is generally good. However, Interchange Sequence Series signs (the signs that show the next three exits), which are used widely in many urban areas, are only used sporadically here. Schematic signs before major interchanges, also widely used in other cities, are conspicuously absent here, although they are being added to new interchanges more often.

Another peculiarity are 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 on US 90 West and I-37 South, signs inside Loop 410 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 control city on the radial freeway is "Downtown San Antonio", guide signs on the corresponding Loop 410 ramps at the same interchange just show "San Antonio".

Unbuilt/cancelled freeways

The only major freeway that was consistently listed in freeway plans over the years but was never built was the Bandera Expressway. This route would have filled what is now an obvious missing link in the system. Two corridors were proposed over the years for this freeway. The first, proposed in 1964, would have started on Bandera Rd. outside Loop 410 and paralleled Bandera to the west south to Guadalupe St. before turning east, crossing I-35, and following Cesar Chavez to I-37, then heading northeast to end at Commerce St. east of downtown (click here for a map.)

The second route, proposed around 1971, would have run along Culebra from I-10 West to Loop 410 (click here for a map.) Opposition due to the projected displacement of thousands of West Side residents eventually killed the project.

A bypass route for I-10 downtown was proposed several times in the '50s, '60s, and '70s to relieve congestion along the original "Downtown Y" expressways of I-10 and I-35. The first proposal would have routed this bypass down the Navidad Street corridor from I-10 at Fulton to US 90 near Zarzamora. Subsequent plans had it running further east, first along or near Brazos Street, then following the railroad right-of-way. This bypass was scrapped with the Bandera Expressway in the mid '70s and a new plan to double-deck I-10 replaced it.

Two small connector freeways branching from US 281 were also proposed in 1964. One would have connected US 281 with I-35 roughly along St. Mary's St. The other would have upgraded San Pedro between Loop 410 and US 281 to a short connector freeway.

Finally, a freeway along Roosevelt Ave., which at the time was US 281, was briefly proposed in the mid '50s.

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, State Highway 16 South and Spur 422, which branches off of I-35 in southwest San Antonio, was likely intended to eventually be a freeway. In fact, the road is officially named the Poteet-Jourdanton Freeway. Strictly technically-speaking, though, it should named Poteet-Jourdanton Expressway as the road is a four lane divided highway with signalized intersections but has frontage roads along several miles. This configuration would have allowed the roadway to be upgraded to a freeway relatively easily by simply building overpasses for the mainlanes at the major intersections. Additionally, the interchange at I-35 used to have direct ramps from I-35 to SP 422 (those ramps were subsequently removed ca. 2010.) When the road was built, most projections saw the city expanding to the south. Instead, San Antonio has grown mostly northward and westward. As a result, the relatively lightly-used Spur 422 remains mostly in its original configuration.

Metropolitan Planning Organization

The Alamo Area Metropolitan Planning Organization (AAMPO) is an agency created in accordance with federal law to coordinate and distribute state and federal transportation funding for the San Antonio area. This area originally included Bexar County and parts of neighboring Comal and Guadalupe County. In 2014, it was expanded to include all of Comal and Guadalupe counties as well as southern Kendall County around Boerne. AAMPO was previously named the San Antonio-Bexar County MPO and, prior to that, the San Antonio-Bexar County Urban Transportation Study (SABCUTS), which was first established in 1963.

HERO/Courtesy Patrol

The Highway Department started the Freeway Courtesy Patrol in San Antonio in 1968 during HemisFair to assist the large volume of visitors coming to the city for the fair. The patrol would help stranded motorists by providing gasoline, water, battery jump starts, tire changes or air, and assistance in making minor roadside mechanical repairs or arranging for towing for vehicles that could not be repaired.

Although it was deemed very successful, the patrol was discontinued after HemisFair due to budgetary issues. A decade later, the program was reinstated with the added duties of clearing disabled vehicles, minor crashes, and debris from the roadways, assisting with traffic control at accident scenes, and placing temporary traffic control devices where needed. Budget issues again caused the program to be discontinued around 2008. 

In 2018, TxDOT obtained funding to restart the local program once more, and the patrol hit the roadways again on August 31, 2020. The Highway Emergency Response Operation (HERO) program covers about 240 miles of local freeways with 28 vehicles. The HERO patrol will provide all the aforementioned services with full coverage operating weekdays from 5 am to 9 pm and limited service at other times. Assistance is free and can be requested by calling 210-732-HERO. During its first 18 months in operation, HERO assisted with over 64,000 incidents, or an average of about one incident every 12 minutes, and provided over 127,000 services to motorists. A Texas Transportation Institute study in 2021 estimated that the HERO program reduced secondary crashes at incident scenes by nearly half.
 

Traffic congestion

Because of the extensive network of freeways, studies show that San Antonio typically suffers lower 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 of the area's freeways now have sections that suffer moderate to severe daily congestion. Expansion work is underway or planned for many of these roads.

Rush hours are generally from 6-9 am, and 3-7 pm.

Hazardous materials route

At 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 in the mid '90s, a plan was finally drafted around the turn of the century and was approved by the Texas Transportation Commission in June 2001.

The map below shows the adopted hazmat routing plan. Designated hazmat routes are marked with the standard "HM" sign such as shown above.

Bexar County hazardous vehicle routes
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 a couple of times a year on average, usually in the form of freezing rain or sleet. Such precipitation, of course, makes driving very hazardous, especially on the numerous overpasses and flyovers. As a result, TxDOT and the San Antonio Police Department 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 brine solution, chemical agents, and sand or 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. Traffic is then routed to the access roads until conditions improve.