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 December 4, 2016
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
Routes with more than one segment are given directional
identifiers. For example, I-35 North is the segment of I-35
of downtown. Interstate 37, Interstate 410, Loop 1604, Spur
SH 151, and the Wurzbach and Kelly Parkways are all
single-segmented. US 90 and US 281 are technically
but one of their two segments runs concurrent with an Interstate, so
only the non-concurrent segments are listed as the US route.
example, US 281 South runs concurrent with I-37, so you will not find a
page for US 281 South; see I-37 instead.
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
east/west but actually runs more north-south, I generally use "inbound"
(i.e. toward downtown) or "outbound" instead.
together: So, what does
"southbound I-35 North" mean? The southbound lanes of Interstate 35 north of downtown.
On each of the pages, I discuss segments of
freeway within what I consider the urbanized area of 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 somewhat from my definition.
time, as the city grows, I have and will extend those termini as
on with the
basic statistics about San Antonio's freeways. All statistics
from the Federal Highway Administration (2010 data) and cover the San
Antonio Urbanized Area. The number in parenthesis is the San
Antonio's rank nationally for that category.
miles of freeway: 228
highway miles: 142
and State highway freeway miles: 86
vehicle miles driven on freeways: 20,258,000
of local roads that are freeways: 3.7%
of total local daily traffic carried on freeways: 53.1%
freeway network was designed on the spoke-and-loop system.
radials, two loops, and a spur make up the 228 mile system.
goal of the system's planners was that no Bexar County resident would
be more than 30 minutes from downtown San Antonio. With
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
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
relatively close freeway access.
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.
map. Lane counts do not
lanes or transitional changes in lane counts.
roads & turnarounds
frontage roads extensively, and San Antonio is no exception.
Locally, they're traditionally referred to as "access roads." Only about
¼ of the freeways here don't have access
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
also lack access roads. In these areas, ramp systems seen in
rest of the world are used.
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.
San Antonio, these are known as "turnarounds" and are so marked.
For more information on frontage roads and turnarounds, see my Texas Highways primer.
Typical San Antonio
barriers and fencing
in Texas have shifted away from conventional Jersey Barrier to Constant
Slope Barriers. All new projects in the San Antonio area
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
phased out. New freeway construction did not include it, and
damaged sections were not replaced. Fifteen miles of fencing
removed in 1996 on Loop 410 to accommodate conduit for TransGuide fiber
optic cable atop the center barrier. The fencing has since
removed from all of the other freeways.
barrier fencing, ramp meter signals are now a thing of the past in San
Antonio. The first ramp control signal was installed in May
on the entrance ramp from Culebra to eastbound I-10. By 1980,
there were nine locations equipped with meter signals. All
one of these were in the downtown area along I-10 or I-35.
exception was the southbound US 281 entrance ramp from eastbound
Basse. San Antonio even boasted a rarity in ramp metering:
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 (this ramp no longer exists) and
one on the entrance from St. Mary's to southbound I-35. These
gates were used to close the entrance ramps
the morning rush hour to help reduce congestion caused by traffic influx and weaving
problems associated with the proximities of those entrances to other
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
along I-10 in 1981,
probably at Woodlawn
entrance to inbound I-10
Ramp metering map
freeways (The "Downtown Y Project")
miles of I-10 and I-35 around downtown San Antonio are
double-decked. These freeways were rebuilt as part of the
million "Downtown Y" project from 1984 to 1991. Named for the
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
canyons or on outdated viaducts. The double-decking added
elevated structures located just to the 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 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 expediting construction and minimizing traffic disruption.
segments are joined together by tensioned cables called tendons located
within ducts inside the segments. The bridges sit atop
single-column support piers.
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
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
the main upper level section, were eventually reinforced with strategic
steel rods. Other than this, the design has fared well, and
double-decked roads have added much needed capacity to the downtown
area freeway network. For photos of the double-decked
For a diagram on how
the upper levels were built, click on the picture below.
Constructing the "Y"
Click on the image to see the
full-sized illustration (69KB)
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
60 or 65 mph. Outside of 410, speed limits are generally 65
Northside and 70 on the Southside. Speed limits jump up to 70
outside of Loop 1604 on the Northside. Loop 410 is 65 mph
of US 90 and 70 mph to the south. Loop 1604 is generally 70
on its freeway segments with some 65 and 55 stretches in Live Oak and
Universal City and 60 mph on the newest segment south of Bandera Road.
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
lane truck restriction
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
to any other freeways within the city of San Antonio.
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.
freeways is generally good. However, Interchange Sequence Series
(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.
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 the corresponding Loop 410 ramps
just show "San Antonio".
freeway that was part of original freeway plans and
never was built was the Bandera/Hill Country Freeway. This road would have
filled what is now an obvious missing link in the network.
routes were proposed over the years for this freeway. The
proposed in 1964, would have started at Bandera and Huebner and
followed Bandera south to Evers. It then would have paralleled
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
The second route, proposed in 1971, would have run along Culebra from
I-10 West to Loop 410. (Click
for a map.) A subsequent plan added a "bypass connector" to be
built in conjunction with this route-- it would have arced
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.
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
north of Loop 410 to 281 to a freeway.
information on the history of the freeway system and proposed routes,
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
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
but has frontage roads along several miles. This
allowed the roadway to be upgraded to a freeway relatively
quickly. Additionally, the interchange at I-35 used to have a
direct ramps from I-35 to SP 422 (they were subsequently removed ca.
2010.) When the road was built, most projections saw the
expanding to the south. Instead, San Antonio has grown
and westward. As a result, the relatively lightly-used Spur
remains mostly in its original configuration.
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
Urbanized 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).
SABCUTS was established in 1963.
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,
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.
extensive network of freeways, studies show that San Antonio suffers lower
levels of overall congestion compared to other large cities, although
it has increased substantially in recent years. On average,
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
for many of these roads. Also, the TransGuide system was implemented
and ease this congestion. Rush hours are generally from
6-9 am, and 3-7 pm.
At one time,
San Antonio was the largest metropolitan area in Texas with no
hazardous cargo routing plan. However, after a series of
accidents near downtown in the mid '90s, a plan was finally drafted around the turn of the century. 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.
map below shows the adopted hazmat routing plan. Designated
hazmat routes are marked with the standard "HC" sign such as shown to the left (or "HM" on newer signs.)
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
(Based on San Antonio Municipal
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 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 chemical agents and
limestone (chat rock) when such
precipitation begins or is predicted. If conditions become too
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 to announce the road closures and direct traffic off the
Traffic is then routed to the access roads until conditions improve.