Location Bandera Rd. (SH 16) from Legend Trail to Diamond K Trail
Status Advanced design. See timeline below.
Summary
Here is a brief summary of this project:
This
project will convert Bandera Rd. to a "superstreet" from Legend Trail
to Diamond K Trail.
This
will modify the intersections at Hausman/Leslie and Cedar Trail to
force traffic on those cross streets to turn right, i.e. left turns and
straight-through movements from those cross streets will be blocked,
but left turns from Bandera Rd. to those cross streets will still be
allowed.
A
downstream turnaround will then allow traffic from the cross street to
make a U-turn to return to their intended direction of travel.
This
is the same configuration as at FM 1560 South.
Doing this reduces the
number of
traffic
signal
phases required to move traffic through the intersection thereby
allowing for longer green times for all movements without extending the
overall cycle time. This allows for more traffic to move through in the
same amount of time, thus reducing
congestion.
While
it seems confusing at first, it's actually pretty easy to navigate.
Studies
of past superstreets show improved safety as well as reduced congestion.
A
new left turn will be built from northbound Bandera Rd. to Legend Trail.
The
crossover at Diamond K Trail will be closed.
Based
on feedback, TxDOT studied possible changes at Circle A Trail, but
determined any changes would result in decreased overall efficiency and
safety.
Description This project will convert Bandera Rd. to a
superstreet from Legend Trail to Diamond K
Trail by converting the intersections at Hausman/Leslie and Cedar Trail
to
restricted-crossing intersections, adding signalized turnarounds at
multiple intermediate locations, and
closing the crossover at Diamond K Trail. This project will also
construct a new signalized left turn from northbound Bandera Rd. to
Legend Trail and will expand the southbound Bandera left turn to
Hausman to two lanes.
The
restricted-crossing intersections will prevent traffic
on Leslie/Hausman and Cedar Trail from going straight or
turning left. Instead, all traffic will make a right turn, then use
a signalized turnaround about 1000 feet downstream to
make a U-turn and continue in the intended direction of travel. Left
turns from Bandera Rd. to those cross streets will still be allowed. To
better visualize this, click on
the following diagram.
LEFT TURN MOVEMENTS DIAGRAM
Click above to see a
simplified diagram of how drivers will make a left turn at
each
intersection
This
project will also build an underground storm drainage system and will
include sidewalks throughout.
The
intersection at FM 1560 South was converted to a superstreet
configuration in 2018, and the intersection at Loop 1604 was converted
to a displaced left turn (DLT) in 2019, so this will close the gap
between these two improved intersections and complete the master plan
for this section of Bandera Rd. TxDOT plans to eventually continue the
superstreet configuration all the way to Triana Pkwy. as traffic
warrants.
A
superstreet is also known by the more technical nomenclature of
"restricted crosssing U-turn" (RCUT) intersection.
Typical superstreet
intersection
How
this project will help The
Hausman/Leslie intersection experiences
significant to severe recurring congestion during both the morning and
evening rush hours. By forcing traffic on Hausman/Leslie to turn right,
this will overlap that traffic with the corresponding left turn from
Bandera and will eliminate the need for green time for the
left
turn and straight-through movements from those streets. The green time
that would have been needed for those movements can instead be
allocated to the remaining movements,
which therefore will allow more traffic through the intersection in the
same
period of time, thus significantly reducing congestion. Additionally,
with a superstreet, each half of the intersection operates independent
of the other, so the signals along each direction of Bandera Rd. can be
timed separately from the other direction, which means better
coordination and synchronization are possible. Simulations show that
this configuration is expected to provide good
long-term congestion relief
based on 20-year traffic projections.
Example Bandera/Hausman-Leslie
Signal Timings Proportion
of each cycle dedicated to each movement. Cycle time for both is equal
(~150 seconds.) Up/down arrows are for north/south Bandera Rd. Current
timing splits are
approximate as they change during the day, but are typical.
Superstreet timings are an example to illustrate how combining the
turning
movements into a single phase using the longest previous phase duration
frees-up time
for the remaining Bandera Rd. through traffic phase without changing
the overall cycle length. It is possible--
and even likely-- that the proportion of time allocated to the turning
movements
could be increased to improve throughput while still providing
increased green time for Bandera Rd. through traffic. Finally, in a
superstreet, the signals on each side of Bandera Rd. can be timed
independently of the other, so the superstreet chart below combines
both directions for simplicity.
Current
Superstreet
For a
deeper explanation on how a superstreet functions and how it improves
traffic flow, see the main superstreets
page.
Although
it's currently not as congested, converting the Cedar Trail
intersection is necessary to provide continuity of improvement. If the
Cedar Trail intersection were not also converted, then it would soon
become a bottleneck as its signal cycle times would be longer
than those on the improved sections upstream from it.
The
new left turn at Legend Trail will provide new direct access to the
Stanton
Run neighborhood from northbound Bandera Rd. That traffic today must
make a U-turn at Cedar Trail, and a U-turn at Cedar Trail will be
prohibited after the
conversion. Since a turnaround for southbound Bandera Rd. will be
necessary
at that location anyway, the left turn to Legend
Trail was a sensible addition. The new signal it introduces
for
southbound Bandera will be integrated into the overall signal
coordination afforded by the superstreet.
Closing
the crossover at Diamond K Trail is necessary as it has become an
increasingly
dangerous intersection and will be more so in the future, and
direct crossovers like this within a superstreet
segment negate the safety and congestion improvements afforded by the
superstreet.
Circle A Trail intersection:
With the previous project to realign the FM 1560 South intersection,
the intersection at Circle A Trail was changed to a
signalized right-in/right-out configuration (i.e. no left turns or
crossovers.)
This was done to streamline traffic operations in the area as that
intersection is fairly close to the new FM 1560 intersection and its
required southbound to northbound turnaround. This has
understandably caused some consternation and grousing among residents
of Helotes Park Estates who are now required to make a right turn and
proceed to a turnaround ¼ of a mile away in order to go south on
Bandera, adding about ½ mile to their trip.
(Some conspiracy-minded residents have even absurdly asserted
that
this configuration is retaliatory in some way.)
Based
on resident feedback, as
part of the planning for the upcoming project, TxDOT asked an
engineering
consultant to re-evaluate the Circle A Trail intersection to determine
if it would be feasible to allow left turns from Circle A to southbound
Bandera. While physically possible, the analysis showed that
doing so
would be problematic from an overall operational standpoint. With a
superstreet, the signals on each direction of the corridor operate
independently and therefore can be better timed for the respective
traffic volumes, thus resulting in better overall traffic flow and
fewer delays for both directions of travel. Converting the Circle A
intersection to allow left turns would require the signals for
northbound and southbound Bandera at that location to return to
interdependent operation, thus negatively impacting the coordination of
the
signals in one or both directions. Those negative impacts would nullify
the benefits of the superstreet and result in that intersection
becoming a new bottleneck, the significance of which
would increase over time as traffic in the corridor increases. There
were also safety issues with reintroducing left turn cross traffic
conflicts at one
location in a corridor that otherwise will not have any. The
negative impacts to the overall corridor operation and safety were
significant enough to
outweigh the benefits for the relatively small volume of traffic from
Circle A Trail.
It's
worth noting that reducing congestion along Bandera benefits
the
residents of Helotes Park Estates and should reduce their overall
travel time in the corridor even with the additional travel time
required to execute the right-turn and U-turn,
and that there are many locations where drivers are required to go a
little out of their way for the benefit of overall efficiency and
safety, including some existing nearby locations along Bandera
Rd.
Timeline Construction is expected to begin in mid 2022 and
take about two years to complete. The construction of an underground
drainage system increased the duration of this project.
FAQ
This looks confusing.
It will cause lots of crashes. This is
always one
of the first knee-jerk assertions made when an unconventional
intersection is introduced. With any change-- even more conventional
changes such
as new signals or lanes-- it naturally takes
drivers a little time to adapt. With a superstreet, because all traffic
on the intersecting
street
is forced to turn right, most confusion is quickly overcome
instinctively once the driver has turned or as the driver follows
other more experienced drivers through the intersection. Additionally,
because all traffic is flowing in the same direction and
is protected by signals, the likelihood of collisions is substantially
reduced, even during the adjustment period. Superstreets also
inherently
improve safety by reducing conflict points (the
point where vehicle paths cross) by half.
Statistics for
superstreets show improved safety. A study for
the
North Carolina DOT showed that superstreets reduced traffic collisions
by 46% and decreased crashes with injuries by 63%. A study of
superstreet intersections in Missouri showed a 54% reduction in
injury and fatal crashes. Many people predicted mayhem at the
Bandera/1604 displaced left-turn intersection, but crashes decreased
44% during the first nine months after it was completed.
How does this crazy design
improve
traffic? How does adding even more traffic signals help?
This intersection design improves traffic because, by forcing all
traffic on the cross street to turn right, the green time for that can
be overlapped with the green time for traffic turning left from Bandera
onto the cross street. This essentially eliminates the green
time
that would be needed for the through
and
left turn movements on the cross street, so that time can then
be
reallocated to
the remaining movements, thus moving more traffic through the
intersection in the same
amount of time. Although there are extra signals, they are all much
more efficient and are better coordinated. See the "How a superstreet works"
section of the main superstreets page
for a deeper explanation of the superstreet "secret sauce".
All they have to do is adjust the
signal timing and that will solve the problem.
It's
a common belief that congestion can be solved by simply
adjusting the signal timing. In some specific cases, that can be true,
but at a very busy intersection like this where there has to be
sufficient green time for eight different movements on every cycle, the
signals can only be optimized so much before the laws of physics win.
For example, the green time on Hausman could be extended to
help clear
out the peak period backups that occur there, but that means the light
will stay red longer for Bandera, which then increases the congestion
there. If the green time on Bandera is then increased to ease those
backups,
that means the light will stay red longer for Hausman and you're right
back where you started. So as you can see, it's really not as easy as
it sounds.
This causes people to have to go
out of their way, which is inconvenient and will require more time to
get across Bandera Rd.
Some
folks understandably are peeved that to
turn left
or go straight on the cross street requires going out of one's way to
accomplish, and think that doing so will increase travel time. While
the former is true and will always be perceived as an
inconvenience by many drivers, wait times in general should be
shorter
and
overall congestion in
the
area reduced. As a result, travel time through the intersection should
typically be
shorter or no longer than it would be at a conventional intersection
even with the added time necessary to use the turnaround. Also
keep
in mind that there are many other examples where traffic
wanting to make a left turn is prohibited from doing so due to a
median, freeway, or one-way street and must therefore turn right
first, then make a downstream U-turn or series of left turns,
so this situation is not unprecedented or unique to superstreets. In
fact, this has already been the case along much of this section of
Bandera Rd. due to the existing median.
This will increase emergency
response times in the area.
TxDOT
worked with the City of Helotes to mitigate concerns with response
times. As a
result, some adjustments to the plans were made including an emergency
vehicle median crossover at Hausman/Leslie, and additional pavement at
the northwest corner of that intersection to facilitate a turnaround
for
emergency vehicles. Again, it's worth noting that long stretches of
Bandera today do not have crossovers, and after the aforementioned
adjustments, the only crossover being lost for emergency vehicles is at
Diamond K Trail, which is being mitigated by ensuring that emergency
vehicles will be able to make a U-turn at Hausman/Leslie.
If
I'm headed south on FM 1560 (Hausman Rd.) and want to go to Wal-Mart,
Starbucks, Bill Miller's, or O'Connor High School, or head
southbound on Bandera Rd., how do I get
there?
At Bandera Rd., you'll turn right, travel about 1000
feet to a turnaround (just past Little Caesar's Pizza), then head
southbound on Bandera where you can turn right at Bill Miller's,
Leslie Rd. (for O'Connor HS), Starbucks, or Wal-Mart,
or continue straight on southbound
Bandera. To return to Hausman Rd. from Bill Miller's, O'Connor,
Starbucks, or
Wal-Mart, you'll turn right onto Bandera Rd. and use a turnaround just
past Wal-Mart to return to Hausman Rd.
Why not build overpasses instead?
Across the country, traffic engineers have
discovered that innovative
intersections like this can produce good congestion relief and safety
at a fraction of the cost and construction time of flyovers and other
traditional
grade-separated solutions. This allows the limited
transportation
dollars to
be saved and used for other needed projects.
The current
and future traffic volumes and safety considerations along Bandera Rd.
aren't sufficient to justify the construction of overpasses or
conversion to a freeway, but they are in the "sweet spot" to support a
superstreet. Furthermore, the right-of-way along Bandera Rd. is not
wide enough for overpasses or a freeway, so the cost would be
considerably higher as additional right-of-way would have to be
obtained, which likely would result in the displacement of many
businesses.
Why are there signals to leave
the turnarounds?
This is to
prevent slower moving vehicles from entering the faster traffic stream
and causing conflicts that could result in collisions or
congestion.
Will the Circle A Trail
intersection be changed to allow left turns again?
No, that intersection is outside the scope of this project. TxDOT did
re-evaluate this intersection when planning this project; see the
discussion of this in the "How this project will help" section above.
Are there any other
superstreets in San
Antonio?
Yes,
there have been two superstreet segments in San Antonio. One was on US
281 north of Loop 1604 and the other was nearby on Loop 1604 between
Braun Rd. and Culebra Rd. Both were built as short-term solutions while
funding for freeway expansions was obtained. The Loop 1604 superstreet
was replaced by a freeway in 2016, and the US 281 superstreet has now
also been replaced by a freeway. Unlike the 281 and 1604
superstreets, which were built as short-term fixes, the superstreet in
Helotes is considered a long-term
solution. A superstreet was also
considered for Bandera Rd. inside Loop 1604, but has been tabled while
a new corridor study
is conducted. A superstreet has also been constructed on a segment of
Loop 337 in New Braunfels.
I heard that the US 281
superstreet was removed was because it was not working well, so why
build one here?
There had been plans to upgrade US 281 in that area to a freeway since
2000. However,
lawsuits by anti-toll activists and environmentalists and a resulting
requirement to conduct a lengthly environmental study delayed the
project for nearly two decades. In 2009, with congestion reaching
severe levels, a superstreet was proposed as a short-term "band-aid" to
help provide some relief, which it did
until
construction on the freeway was finally able to get started in 2017.
The expected traffic volumes on
US 281 exceed what a superstreet can optimally handle, so a superstreet
would never have been planned as a permanent solution there. However,
the current
and projected traffic volumes on Bandera Rd. are in the "sweet spot"
for a superstreet to have a significant long-term positive impact. For
comparison, traffic volumes on the section of US 281 with the
superstreet ranged from 55,000 at Marshall Rd. to 100,000 at Redland
Rd., while on Bandera they range from 26,000 just west of FM 1560 South
to 43,000 at Loop 1604.
Who came up with this cockamamie
design? This won't work and is just a waste of money.
The
superstreet design has been used in several US states for more than 20
years and has a proven
track record of improving traffic wherever it has been implemented.
Both the US 281 and Loop 1604 superstreets showed appreciable
improvments, and computer modeling shows that this superstreet will do
the same. A superstreet
is one of several types of "innovative" or "alternative" intersection
designs
being implemented across the country at intersections
where improvements from conventional expansions will be short-lived but
where conditions do
not warrant more expensive traditional upgrades such as
flyovers. Many people expressed similar doubts about the nearby
Bandera/1604 DLT intersection, but the new design has substantially
reduced congestion and crashes there.
Schematic Click
on
the image below to open the detailed schematic for this
project from TxDOT with my own annotations added to help clarify and
explain the various elements. The schematic will
open in a new window that you can scroll and zoom.
DETAILED PROJECT SCHEMATIC
Click above to see the detailed
annotated schematic for
this project
Video TxDOT has a good video that describes this project:
NOTICE
The information provided on this website is provided on an "as-is" basis without
warranties of any kind either express or implied. The author and his agents
make no warranties or representations of any kind concerning any information
contained in this website. This website is provided only as general
information. The author expressly disclaims all liability with respect to
actions taken or not taken based upon the information contained herein or with
respect to any errors or omissions in such information. All opinions expressed
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