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Texas Highwayman Pages > San Antonio Freeway
System > Primer
(The FAQ section that
previously was on this page has moved here.)
Site conventions
Freeway segments:
Information about the various freeways is divided by freeway segment.
Segments are based on (what I consider) logical divisions of the routes.
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 bisegmented, but one of their two segments is
multiplexed with an Interstate, so only the non-multiplexed 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"
(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.
Now, on with the primer...
Freeway system statistics
Below are some basic statistics
about San Antonio's freeways. All statistics are from the Texas
Transportation Institute (2003 data) and cover the San Antonio Urbanized
Area.
- Total centerline miles of
freeway: 211
- Total lane miles of freeway:
1,075
- Total number of miles driven
in SA daily on all roadways: 31.4 million
- Total number of miles driven
daily on freeways: 16.1 million
- Percent of total miles driven
daily in SA served by freeways: 51.3%
- Average daily traffic per
freeway lane: 14,976
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 roughly 200 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 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 close
freeway access.
In the past, most of the city's
busy freeway segments outside downtown were six lanes, but in recent
years, many of them have been expanded to eight and 10 lanes, and more
such projects are on the horizon. In 2005, about nine miles of
freeway were 10 lanes; that will increase threefold by
2010.
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 US 90 West. The downtown freeways also lack
access roads. In these areas, ramp systems seen in the rest of the world
are used.
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.
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 the new 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 meters
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 oddity 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. It was upgraded in early 2005
with new signal units, but subsequently removed in June 2005.
Ramp meter
signal along I-10 in 1981, probably at Woodlawn entrance
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 an 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"
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 north of New Braunfels.
Most freeways inside of Loop 410 have now gone to 60 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 60 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, most of the minimum speed limit signs have been removed during
the past decade or so and only a handful remain, mostly around
downtown.
Left lane truck restriction
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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.
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 is
currently being investigated as are other possible corridors in
the San Antonio area. |
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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 much less frequently here. Segments with ISS signs
include I-35 North between 410 and 1604, parts of I-10 West between 410
and DeZevala, and I-35 South from US 90 to Zarzamora. IIS signs
are also used sporadically in other areas of the city. 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" (new signs approaching Loop 410 now 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 Durango 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.
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. Most people (including myself)
refer to it as the Poteet-Jourdanton Highway, though, and rightfully so.
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 in its original configuration,
although the recent construction of a Toyota manufacturing plant just
south of the city along SH 16 is expected to increase development and
traffic in the area.
Metropolitan Planning Organization
The San Antonio/Bexar County
Metropolitan Planning Organization (MPO) is the agency charged with
designating transportation projects to receive federal
transportation funding for the San Antonio Urbanized Area. This
area currently includes Bexar County and parts of neighboring Comal and
Guadalupe County. The MPO replaced the San Antonio-Bexar County
Urban Transportation Study (SABCUTS).
Courtesy Patrol
TxDOT operates a free Courtesy
Patrol on the area's freeways to assist stranded motorists, clear debris
from the roadways, and assist at accident scenes. Courtesy Patrol
workers provide gasoline, water, battery jump starts and tire
changes, but they do not make mechanical repairs. The patrol
trucks are also equipped with fire extinguishers and traffic control
equipment.
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 permanently in 1979.
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, US
281, I-10, and I-35 all have areas of moderate to severe daily
congestion. Expansion work is underway or planned for 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
 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, 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.
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 when such
precipitation begins, using chemical agents and crushed limestone (chat
rock). 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. Traffic is then routed to the access roads until
conditions improve.
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