Antonio Area Freeway System
151/Alamo Ranch Parkway at Loop 1604
page last updated June 27,
the history of various projects in the Loop 1604 - SH 151 - Alamo Ranch
Parkway (ARP) -
Westwood Loop area, discusses future plans, and answers frequently
Many people just assume that either the City of San Antonio or TxDOT is
responsible for all the roads in
this area. However, that's not the case. TxDOT is responsible
SH 151 and Loop 1604 and their access roads. Bexar County is
responsible for Alamo Ranch
Parkway starting about 800 feet west of Loop 1604 including
the intersection at Westwood Loop, while TxDOT is responsible to the
that point. There are signs on Alamo Ranch
Parkway that mark where Bexar County's jurisdiction begins (see below.)
The City of
San Antonio is not responsible for any of the roads in this immediate
(at right) marking the beginning of Bexar County jurisdiction on Alamo
(Photo by Brian Purcell)
from Loop 1604
southbound to SH 151 eastbound removed all that traffic from the
southbound access road and the previous
signalized intersection to cross Loop 1604. The new
overpass connecting SH
151 to ARP improved the connectivity between those
this was done to reduce congestion on both Loop
1604 access roads south of Culebra as SH 151 traffic destined for ARP
and southbound Loop 1604 no longer has to use those access roads and
the turnaround at Culebra. In
addition, traffic from
Culebra headed to SH 151 now uses routes other than the southbound
Original TxDOT project (completed in 2017)
The original TxDOT project constructed a flyover
southbound Loop 1604 to SH 151 and an overpass connecting SH 151 to
Alamo Ranch Parkway at
Westwood Loop. This overpass
a previous signalized
intersection for eastbound traffic crossing Loop 1604 and a circuitous
route along the Loop 1604 access roads for westbound traffic.
The flyover and overpass allowed the signalized at-grade
intersection on Loop
1604 at SH 151 to be removed, which was necessary to extend the Loop
1604 freeway to the south.
Generalized 151/1604 area traffic
patterns before and after ARP overpass
Illustrates a major intent of the original state project
to remove traffic from the overcrowded 1604 access roads
and 1604/Culebra intersection
on this project began in
April 2015. The flyover from southbound Loop 1604 to SH
151 opened to traffic July 30, 2016. The ARP overpass
opened on December 17, 2016.
traffic signal (completed
intersection at ARP and Westwood Loop was originally a two-way stop
(stop signs on Westwood Loop), then a four-way stop. To accommodate the
expected increase in traffic, the county planned to have a traffic
signal at ARP and Westwood Loop ready in time for the opening of the
overpass from SH 151. However, the Casa Blanca theater was announced
after the county had already started their planning process for
the signal, so it required engineering for the signal to be paused
while the county waited for the driveway and turn lane plans from
theater developer, thus delaying the
project. The signals
finally went into operation on February 27, 2017.
Loop turn issues
to numerous issues with drivers making aggressive lane changes in order
to make a right or left turn at Westwood Loop from westbound ARP,
flexible pylons were installed separating the SH 151 and Loop
approach lanes. However, many drivers simply ignored these and drove
them or made illegal turns at the intersection. The pylons were
replaced a few months later with a concrete island.
for a "split-phase" signal were considered but dismissed after modeling
showed that the increased cycle time required for it would
substantially increase congestion on all approaches.
Installation of pylons on westbound ARP at Westwood Loop to prevent
These were subsequently replaced by a concrete island.
(Photo courtesy of Josh Donat,
ARP/Westwood Loop additional
westbound through lane project (completed
in May 2019)
to increasing traffic congestion on westbound SH 151
Parkway/Westwood Loop intersection, the county built an
additional lane on westbound ARP through the Westwood Loop
additional lane allowed the left lane
coming from SH 151, which used to be a left turn only lane, to become a
left turn/straight option lane instead, i.e. it provided two through
lanes from 151 through the intersection.
at Westwood Loop (under construction)
finally resolve the turning and associated safety issues at Westwood
Loop discussed above, funding was obtained to build an overpass
westbound ARP traffic over Westwood Loop; see the Alamo
Ranch Parkway at Westwood Loop project page for
Westbound SH 151
ramp to northbound Loop 1604 (planned
The obsolete hairpin entrance to northbound Loop 1604 from SH 151 will
replaced in the near future by a new direct connector as part of an expansion
project on SH 151.
The projects around this location illustrate the
incremental method that road improvements often take and epitomizes the
concept of "Don't let
the perfect be the
enemy of the good."
- Why did they make a highway end
at a traffic signal?
It may seem like that's the case since the 151
continue straight onto Alamo Ranch Parkway (ARP), but traffic coming
had to go somewhere onto ARP, and ARP is a surface street with
signalized intersections, so that's just how
it worked out. This situation is not unheard of and is found in
many other cities.
The goal of the original TxDOT project was to provide a
direct connection from 151 to ARP so that traffic would no longer have
to follow the access road to Culebra, turn around, and go back on the
opposite access road to reach ARP, which
substantial congestion on those access roads (see
traffic patterns maps above.) Also,
the project was needed so that traffic
going from ARP to 151 would not have to cross Loop 1604 at a the
signalized intersection, which had to be removed in order to upgrade
Loop 1604 to a freeway.
Since ARP lies directly ahead of the end of 151, the route must
inherently go straight
from 151 to ARP. Therefore, it gives the impression that the
highway keeps going over 1604 and suddenly ends at an intersection, but
you'll notice that the speed limit decreases to 45 mph as you approach
and there are large yellow "FREEWAY ENDS - SIGNAL AHEAD" signs that
tell you the
freeway is ending and that you are transitioning to a surface street.
overpass is really just a long, straight exit from
151 to ARP-- it just
happens to be at the end of the
is a case where drivers need to pay attention and adjust their
expectations. It's a location that required an
anomalous design (a situation complicated by an
endangered species finding; more on that below.) Perhaps drivers would
have more intuitively
understood that they're exiting the freeway
if the 151 access road had been extended over Loop 1604
instead of the mainlanes and ARP-bound traffic had to
"exit" and use that. However,
there still would have been the same issues where that access road
transitioned to ARP.
- This configuration causes
traffic from 151 to ARP back up at Westwood Loop.
traffic queues at that signal just as it does anywhere traffic
leaves a freeway and encounters a controlled intersection such as it
exit ramps and access roads elsewhere in the city and where freeways
end and become surface
roads (e.g. Loop 1604 at US 90.) As mentioned above, this is
exit from 151 to ARP-- it just
happens to be a straight exit at the end of 151. As such,
no reason to expect this location wouldn't have backups like any other
highly-trafficked exit from a freeway to a surface road. Furthermore,
traffic backed up there prior to the overpass being built and
never been claimed that the overpass would solve that. Instead,
the direct overpass is an improvement over the previous circuitous
from 151 to ARP via the Loop 1604 access roads and Culebra
- Couldn't they have extended the
overpass over Westwood Loop?
but the state's right-of-way doesn't extend that far, and so this
intersection was outside the scope of that project. In
addition, it would
have increased the cost of that project. They
the best they could with the funding they had at the time. Road
in fast growing areas with limited funding will always be an exercise
in incremental improvements.
That said, funding has been obtained to construct an overpass for
westbound ARP over Westwood Loop; see the Alamo
Ranch Parkway at Westwood Loop project page for
- Are there any future plans to
improve the intersection of ARP and Westwood Loop?
Yes, funding has been obtained to construct an overpass for
westbound ARP over Westwood Loop; see the Alamo
Ranch Parkway at Westwood Loop project page for
- What other improvements were
considered for ARP and Westwood Loop?
Previously-considered plans to
convert the intersection to a
"super street" configuration were dropped as was a
previous proposal to change the westbound signals
to a "split-phase" where the approaches from SH 151 and Loop
1604 would each have had their own green phase, thus allowing left and
right turns from
each (similar to the McCullough exit from southbound I-35 downtown.) It
was determined that changing to a split-phase would
have extended the cycle length excessively, thereby increasing
- Couldn't they have built an
underpass under Loop 1604 instead of the overpass?
That actually was the original plan, but the discovery of a
federally-protected endangered spider during
construction forced TxDOT to stop work and redesign the
project to go over the protected habitat
of that spider. The good news is that the direct connector
from southbound Loop 1604 to 151 was not included in that original
so the discovery of the spider resulted in that improvement
being expedited as part of the new project.
- Why didn't they plan for the
increase in traffic caused by the overpass?
Obviously, planners knew that traffic would increase with
the opening of the overpass. The challenge is
something known as "latent demand" and "induced demand". These are the
significant number of people who were using
alternate routes to avoid the congestion and/or inconvenience of the
previous 151 to ARP route, and the new development in an area that
results from the improved access. While planners can do studies to
attempt to estimate what that latent and induced demand might be, it's
virtually impossible for anyone without a crystal ball to know for sure
what that demand is until the new road opens and that traffic
especially in an area like Alamo Ranch that's growing so
Why is there
a signalized intersection for the ramp to southbound Loop 1604
instead of a flyover?
There was not enough funding for a flyover for that connection, and,
the road network in this part of the city, planners estimated that
there should not be a
considerable amount of traffic making that turn, so this was
the compromise. The peak period for traffic making
that turn is in the evening when eastbound ARP/151 traffic is
typically lighter. Traffic counts on that ramp since it has
opened have validated planners' assumptions.
- Why did they only build the
connector from southbound 1604 to 151?
The simple answer is funding. They only had enough funding
to construct one connector, and that's the one with the most traffic
and most "bang for the buck". A new direct connector from westbound 151
to northbound 1604 will be built as part of an upcoming
expansion of SH 151.
- Why didn't they make the
connector from southbound 1604 to 151 two lanes?
Funding for that connector was limited.
Furthermore, there are not enough lanes downstream on 151 to receive
two lanes from the connector plus the lanes coming from ARP plus the
ramp from northbound 1604. Making that connector two lanes would have
resulted in a pretty significant bottleneck where it merges into 151.
That said, a future upgrade to that connector is envisioned.
- Why did they close the Wiseman
exit ramp on eastbound SH 151?
Technically, there wasn't an exit there before. Traffic
coming from Loop 1604 previously was on the access road and could
either enter the SH
151 mainlanes just before Wiseman or stay on the access road to
Wiseman. The new
connector from 1604 enters the 151 mainlanes
directly, not the access road.
The reason why they didn't add an eastbound exit to
Wiseman from the Loop 1604 connector is because there wasn't sufficient
space to do so. From the end of the on-ramp coming from
northbound 1604, they would need a minimum of 1,500 feet for a weave
area that would be safe and minimize possible congestion. At
the 1,500 foot mark, the exit to Wiseman would be quite steep and would
the end of the off-ramp much too close to the Wiseman intersection
(less than 500 feet), which means drivers wanting to turn right onto
Wiseman would have to make a sharp cut across the access road, which
might be difficult if more than a few vehicles were stopped at the
signal and would mean that traffic would likely back
up onto the exit ramp during peak periods.
- Will the hairpin connector from
151 to northbound 1604 be replaced?
TxDOT did not have enough funding in the 1604/151/ARP project to
ramp. However, a new direct connector for that turn will be included
in a future project to widen SH 151.
- Will there be a flyover or ramp
from eastbound ARP to northbound Loop 1604?
No, there are no plans at this time for such a connector. Planners are
keeping it in mind as they make other improvements in the area so as to
not do anything that would interfere with one eventually being built.
- Why is there no entrance
ramp to SH 151 from Culebra?
The decision to not include an entrance
from Culebra to SH 151 was based on several factors:
mentioned a few
bullet points above, planners are considering long-term plans
that would expand the soutbound Loop 1604 flyover to SH 151. To do so
actually require constructing a new flyover. If they do that, they
likely would retain the existing flyover and repurpose it as a
connector from the southbound Loop 1604 access road to SH 151.
- The volume of traffic now and especially
in the future needing to exit from southbound 1604 to ARP likely
exceeds that of
traffic needing to get from Culebra to SH 151; this made an
exit for ARP a higher priority than an entrance from Culebra.
- There is only room for one surface ramp in that
area and the cost for a "braided" ramp was probhibitve.
are reasonable alternatives to get to SH 151 from Culebra whereas
there are very limited possibilities to get from southbound 1604
to ARP that don't add significantly to existing congestion (i.e.
southbound Loop 1604 at Culebra.).
entrance from Culebra onto the SH 151 connector would have resulted in
significant congestionon the
connector during peak periods caused
by the stream of slower-moving traffic entering from Culebra trying to
with the stream of faster-moving traffic coming from Loop 1604, all
while moving uphill to the connector. This congestion would have
backed-up onto Loop 1604 as well as onto the access road and possibly
intersection at Culebra.
- They should fire the idiot who
If after reading the information above you still feel that way, see this