Antonio Area Freeway System
INFO: Loop 1604 at SH 151
page last updated March 15, 2018
This project is complete.
151 at Loop 1604/Alamo Ranch Parkway (ARP)
This project constructed an elevated direct connector ramp
southbound Loop 1604 to SH 151. Additionally, it added an
overpass connecting SH 151 to ARP at Westwood Loop; this replaced
intersection for traffic crossing Loop 1604.
project will help
Providing a new direct connection from Loop 1604
southbound to SH 151 eastbound removes all that traffic from the
existing SB access road and previous signalized intersection. The new
overpass connecting SH
151 to ARP improves the connectivity between those
this should especially reduce congestion on the Loop
1604 access roads south of Culebra as SH 151 traffic destined for ARP and SB Loop 1604
will no longer have to use the turnaround there. In addition, traffic from
Culebra headed to SH 151 will use now other routes, further reducing congestion on those access roads.
This project also eliminated the signalized at-grade
intersection on Loop
1604 at SH 151, which is necessary to extend the freeway south.
The resulting change in traffic patterns should also
translate into some
improvements in the overall operation of the Loop 1604/Culebra
Macro 151/1604 area traffic
patterns before and after ARP overpass
Illustrates a major intent of this project
traffic away from the overcrowded 1604 access roads
and 1604/Culebra intersection
April 2015. The
direct connector from SB Loop 1604 to SH
151 opened to traffic July 30, 2016. The ARP overpass
opened on December 17, 2016. The traffic signals at Westwood Loop went into full operation on February 27, 2017.
This project 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 mainlanes
straight onto ARP, but traffic coming from 151 had to go somewhere onto
ARP, and ARP is a surface street with intersections, so that's just how
it worked out. This situation is not uncommon and is found in
many other cities.
The goal of this project was to provide a
direct connector from 151 to ARP so that traffic would no longer have
to go to Culebra, turnaround, and go back to reach ARP, which
substantial congestion on those access roads, and also so that traffic
going from ARP to 151 would not have to cross Loop 1604 at an at-grade
intersection (see traffic patterns maps above.) Since ARP
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.
Therefore, the overpass is
essentially a long exit from 151 to ARP-- it just
happens to be a straight exit 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 instinctively
understood that they're exiting the freeway
if the 151 access road had been extended over Loop 1604
of the mainlanes and ARP-bound traffic had to
exit and use
there still would have been the same issues where that connected to ARP.
- Won't this cause westbound
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 and where freeways end and become surface
roads (e.g. Loop 1604 at Wiseman.) As mentioned above, this is essentially an
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 this project
and it has
never been claimed that this project would solve that.
the direct overpass is an improvement over the previous circuitous route
from 151 to ARP.
- Couldn't they have extended the
overpass over Westwood Loop?
but the state's right-of-way doesn't extend that far, plus it would
have substantially increased the cost of the project. They
the best they could with the funding they had. Road
in fast growing areas with limited funding will always be an exercise
in incremental improvements.
- Are there any future plans to improve the intersection of ARP and Westwood Loop?
current intersection is considered to be an interim improvement as
planners know that growing traffic will overwhelm it before too long.
In the meantime, to prevent the illegal turning/crossover
situation on the
westbound side, the county has added a concrete curb where
the flexible pylons previously were. In Summer 2018, an
additional through lane from SH 151 onto Alamo
Ranch Parkway will be constructed; this will allow the far left lane
coming from SH 151 to become a straight/left option lane.
The lane will then merge into the existing two lanes about 250
yards downstream from the intersection. Previously-considered plans to
convert the intersection to a
"super-street" configuration have been tabled for now as has a
previous proposal to change the WB signals
to a "split-phase", where the SH 151 and Loop 1604 approaches would
have had their own green phase (thus allowing left and right turns from
each). It was determined that changing to a split-phase would
have extended the cycle length which in turn would have increased
congestion and that doing so was unnecessary as there are other
convenient routes to reach those destinations.
Pylons being installed on westbound ARP at Westwood Loop to prevent problematic
lane changes; these have since been replaced by a concrete curb
(Photo courtesy of Josh Donat, TxDOT)
- Why is the left lane coming from
151 a turn-only lane?
are only two lanes
on ARP to receive traffic crossing Westwood Loop. With
traffic coming from both Loop 1604 and from 151, dividing that capacity between the two (i.e. one lane each)
was appropriate. That means that the "extra" lane coming from
had to either be dropped prior to Westwood Loop or could flow into the
left-only lane. It was decided that the volume of traffic
headed to the theater, future apartments, and other planned future
development there would be sufficient to make that
left-only lane there beneficial.
- Could they have built an
underpass under Loop 1604 instead of the overpass?
actually was the original plan, but the discovery of a
federally-protected endangered spider during construction of that
forced TxDOT to redesign the project to go over the protected habitat
of that spider. The good news is that the direct connector
southbound Loop 1604 to 151 was not included in that original project,
so the discovery of the spider resulted in that improvement.
- Why didn't they plan for the
increase in traffic caused by the overpass?
Obviously, planners knew that traffic would increase with
opening of the overpass. The challenge is
something known as "latent demand".
This means that there were a significant number of people
alternate routes to avoid the congestion and/or inconvenience of the
previous 151 to ARP route. While planners can do studies to
attempt to estimate what that latent demand might be, it's virtually
impossible for anyone without a crystal ball to know for sure
that demand is until the new road opens and that traffic materializes,
especially in an area like AR that's growing so rapidly. That
said, the overpass and ARP have ample capacity for the expected traffic
once the situation at Westwood Loop is sorted-out.
- Why is there
a signalized intersection for the ramp to southbound Loop 1604
instead of a flyover?
was not enough funding for a flyover for that connection, so this was
compromise. An elevated direct connector will likely replace
it in the future. The highest traffic volume making
that turn should be in the evening when eastbound ARP/151 traffic is
typically lighter. (Traffic counts on that ramp since it has
opened have shown a relatively miniscule volume of traffic using it.)
- Why did they only build the
connector from southbound 1604 to 151?
The simple answer is funding. They only had enough
to construct one connector, and that's the one with the most traffic
and most "bang for the buck".
- Why didn't they make the
connector from southbound 1604 to 151 two lanes?
There are not enough lanes downstream on 151 to receive two
from the connector plus the lanes coming from ARP and the entrance
ramp from northbound 1604. Making that connector
two lanes would have
resulted in a bottleneck where it merges into 151. Most
freeway-to-freeway connectors are only a single lane.
- Why did they close the Wiseman
exit ramp on eastbound SH 151?
Technically, there wasn't an exit there before.
coming from Loop 1604 was on the access road and could either enter SH
151 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. That said, 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
1,500 foot mark, the exit to Wiseman would be quite steep and would put
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. It would
also mean that traffic would likely back up onto the exit ramp during peak
- Will the hairpin connector from
151 to northbound 1604 be replaced?
Not at this time. TxDOT is aware of the issues that
causes, but did not have enough funding in this project to improve that
- Will there be a ramp from
eastbound ARP to northbound Loop 1604?
there are no plans at this time for such a connector. It
could be included in future improvements to the interchange.
- 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:
- The volume of traffic now and especially
in the future
needing to get from southbound 1604 to ARP 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 ramp in that area.
are good local alternatives to get to SH 151 from Culebra whereas
there are limited ways to get from southbound 1604
entrance from Culebra onto the SH 151 connector would have resulted in
significant congestion on the
peak periods caused
stream of slower-moving traffic entering from Culebra trying to merge
with a stream of faster-moving traffic coming from Loop 1604 all while
moving uphill to the connector. This congestion would have
onto Loop 1604 as well as onto the access road and possibly into the
intersection at Culebra.
this just make traffic worse and create longer commutes from Culebra to
it may seem like not providing traffic from Culebra a direct entrance
to 151 will make things worse for those commuters, the larger project
improve things in the long run. With the overpass from ARP to
151 now complete, traffic coming from outside 1604 can now
use ARP to get directly to 151, which should be faster than the
previous route. And for traffic coming from inside 1604, the
to Wiseman to 151 route is about the same distance and time as the
previous route. In general, this diversion of traffic to
alternate routes should actually somewhat reduce congestion in the
Loop 1604/Culebra intersection. (See the traffic patterns map
at the top of this page.)
- They should fire the idiot who
If after reading the information
above you still feel that way, see this page.
In addition to the information above, I have a blog
post about the recent controversy surrounding this project here.
on the image below to see an annotated overview schematic of this
project. The base schematic is courtesy of TxDOT; the
annotations are my own. The
schematic shows the preliminary plans as presented to the public prior
to construction and are subject to change.
on image above to see larger schematic