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Other San
Antonio Area Roads
Bandera
Road/Leon Valley study |
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| This page last updated October 27, 2022 |
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The
proposals on this page are still in development
The
cities of San Antonio and Leon Valley and the Texas Department of
Transportation are currently in the midst of a years-long study to
determine how to improve Bandera Rd. As a result, the details discussed below are subject to change.
This page includes details about previous concepts that are no
longer being considered in order to provide context and background to
the
ongoing studies. |
Bandera
Road (SH 16) between
Loops 410 and 1604 in Leon Valley and Northwest San Antonio is one of
the most congested road in the region. About 70,000 vehicles a day use
the southern half of the route and about 40,000 use the
northern
half.
To put that into perspective, the section of Loop 410 on the
South
Side between
I-35 and I-37 carries about 50,000 vehicles per day, and the stretch
of Loop 1604 between SH 151 and US 90 carries less than 40,000
vehicles per day. So improvements
to
Bandera Road are urgently needed and have been for decades, but the
road has languished with only a few minor improvements since the mid
'80s.
The problem hasn't been that officials haven't recognized
this need; a freeway was actually planned for Bandera Rd. during the
1950s and 60s, and more recently, there
have
been at least seven studies and proposals to upgrade Bandera Rd. over
the past three
decades. The primary snag has
been finding improvements that are amenable to the
City of
Leon Valley. A
flyover proposal by TxDOT back
around
1990 was shot down by Leon Valley leaders, and an alternative plan
that proposed building an elevated highway
along Leon Creek and bypassing Leon Valley altogether also was
nixed for other reasons. This schism has resulted in the repeated
stalling of efforts to make major improvements to Bandera Rd.
Then,
in 2009, the Alamo Area Regional Mobility Authority (ARMA) included
Bandera Rd. in their regional toll system plan.
The conceptual
proposal was an elevated tollway along the length of Bandera between
the loops. However, subsequent feasibility studies-- and simmering
opposition from several constituencies-- scuttled that plan. TxDOT
subsequently
took over studying other options to relieve congestion in the corridor.
Current planning
As
discussed above, TxDOT has been studying a number of options to reduce
congestion and improve safety on Bandera Rd. for many years. In 2018,
the City of San Antonio joined those ongoing Bandera Rd. planning
efforts and launched a
"community planning process" to develop a overarching plan for
transportation, land
use, urban design, and economic development along Bandera Road. The
first public meeting in this combined planning effort was held April
29th, 2019, with additional
meetings held in December 2019, June 2021, and October 2022.
Traffic study
In order to determine the best options for improvements, TxDOT studied
traffic patterns along the corridor and
identified three major traffic movements that need to be addressed:
- Through traffic:
Current studies indicate that about 9-15% of traffic on Bandera travels
from Loop 410 to Loop 1604. However, with continuing growth along
Bandera outside
Loop 1604, it is expected that percentage will increase.
- Local traffic: This
is traffic with origins and/or destinations in the Bandera Road
corridor (i.e. local residents and/or patrons of local businesses.)
- "Zig-zag" traffic:
This consists of traffic using a portion of Bandera for cross
connectivity between
a thoroughfare on one side of Bandera to another thoroughfare on the
other side of Bandera. Analysis of traffic data revealed that there
are three of these major
movements:
- Eckhert
- Mainland/Guilbeau
- Loop
410 - Grissom
- Loop
1604 - Prue
Major "zig-zag" traffic patterns
on
Bandera Rd.
These "zig-zag" movements create two unique problems:
- They
inject a large amount of traffic into the through route for a short
distance.
- They
generate massive left turn movements at multiple intersections. Left
turns are the most inefficient traffic movement and require
substantially more signal time, which then reduces the amount of signal
time available for the other approaches.
The traffic study also looked
at projected traffic volumes through the year 2047 which showed
increases of around 40% south of Braun to over 85% north of there.
Options evaluated
With those
traffic patterns in mind, several options were evaluated:
- Conventional widening:
This plan would add one lane in each direction to the existing lanes
(i.e. eight lanes from the Loop 410 ramps to Guilbeau and six lanes
from there to Loop 1604), make conventional intersection improvements,
and improve
access management (i.e. limiting driveways.)
- RCUT: This
would convert all intersections in the corridor to
"Restricted Crossing U-Turn" (RCUT) intersections.
Additional through lanes could also be included in this
plan. This option is discussed in more detail below.
- Boulevard:
This concept would add a two-lane frontage road on each side of the
existing mainlanes, which would be rebuilt. This option is discussed in
more detail below.
- Thoroughfare network improvements:
TxDOT identified and modeled several possible thoroughfare connections
that could remove much of the
"zig-zag" traffic from the section of Bandera. Of
the
options explored, a connector from Eckhert at Abe Lincoln to Bandera at
Mainland and/or Guilbeau had the most promise. The City of San Antonio
has agreed to study this further and would be responsible for building
it should it be determined to be feasible.
- Reversible connector: This
concept would build an elevated, reversible roadway to provide a direct
express lane for one or more of the
"zig-zag" traffic movements. It would be reversible, meaning it would
change direction between the morning and afternoon rush hours to flow
in the direction of peak traffic.
- Traditional freeway:
This would build a standard freeway corridor with mainlanes,
overpasses, ramps, and access roads..
- Elevated throughway:
This proposal, commonly-referred to as the
"flyover" plan, would consist of shifting the
existing lanes slightly further outward and building an
elevated roadway on piers located in the center median. This
elevated roadway, running from Loop 410 to Loop
1604, would overhang the surface lanes and consist of a
single lane and a shoulder in each direction to
carry through traffic, similar to the flyovers connecting Bandera and
Loop 410. Due to right-of-way constraints that limit possible
"touch-down" locations for
entrance and exit ramps, access points along the elevated section would
be very limited. The elevated lanes would tie-into the existing
flyovers connecting to Loop 410. Although this was included as a
possibility in an early toll road plan, this option would not be
tolled.
After the
initial study, the options were winnowed down to four:
- Conventional widening and
intersection improvements:
This would widen Bandera to four lanes each way, add turn lanes at
intersections, and eliminate the "split phasing" of the traffic signals
at many of the intersections that allows only one direction of the
cross street to have a green
signal at a time. This option provided the second lowest reduction in
congestion reduction meeting only 62-66% of 2047 projected demand,
mostly due to the remaining inherent inefficiencies of the
intersections.
- Boulevard: This
option is discussed in more detail below. Of the four options studied,
this provided the least reduction in congestion meeting only 57-64% of
2047 projected demand (again, mostly due to remaining inherent
inefficiencies at the intersections), actually increased intersection
conflicts because of the addition of frontage roads, and required the
the most additional right-of-way.
- RCUT: This option is
discussed in more detail below. It provided good congestion reduction
meeting 84% of projected 2047 demand.
- RCUT with grade separations:
This would combine both the RCUT option along the entire corridor
and the "flyover" plan from the Loop 410
connectors to Guilbeau.
However, the flyover lanes would instead descend below ground level
through Leon Valley. This option had the best reduction of congestion
meeting 90-93% of projected 2047 demand. However, it was also by far
the most expensive at $410 million, had the longest construction
duration and impact, and had the most long-term maintenance
costs, mostly due to the depressed segment needing stormwater pumping,
air ventilation, and fire protection.
TxDOT
branded all the options except the boulevard as "parkway"
options, meaning that in addition to expansion, efforts would be made
to beautify the corridor. (The boulevard proposal would also include
beautification efforts, although they would be more limited than the other options.) All the
options would also consolidate driveways and median crossovers.
After further study, the study participants settled on the RCUT plan as
the preferred option as it met the needs of congestion relief, safety
improvement, and ancillary aesthetic, pedestrian, and bicycle
enhancements at a reasonable cost.
With
that decision, the next steps will be to finalize buy-in from the
stakeholders, then move to advanced design and planning, environmental
study and clearance, and final engineering. At the same time, efforts
will be made to identify funding as there is currently no funding
earmarked for this project. If all goes well, construction could begin
around 2024 and be complete around 2027.
Projected 2047 travel time comparisons for the various options
 
* Morning (AM) peak period is from 6 a.m. to 9 a.m. Afternoon (PM) peak period is form 4 p.m. to 7 p.m.
**
No-build travel time on Guilbeau Road to Eckhert Road (AM) trip is due
to the SH 16 bottleneck north of Guilbeau Road, which limits the volume
of traffic that can reach this segment of SH 16 in the AM peak period.
RCUT proposal
Of the four options studied, the RCUT concept was selected in 2022 as the preferred option to carry forward. This would convert the
nearly all of the signalized intersections
on Bandera Rd. to Restricted Crossing U-Turn (RCUT) intersections, add
signalized
turnarounds at
multiple intermediate locations, close all of the unsignalized
crossovers, and eliminate the signalized intersections at Reindeer
Trail and Poss Rd. This plan would also widen Bandera to four lanes in each
direction, consolidate many of the driveways along the corridor, add
pedestrian and bicycle amenities, and add curbs and storm drains.
The
RCUT intersections will prevent traffic
on the intersecting roads from going straight or
turning left. Instead, all traffic will make a right turn, then use
a signalized turnaround typically 1000 or so 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. An
RCUT intersection is also known as a "superstreet".
Typical RCUT
intersection
How
this will help
Most of
the intersections on Bandera experience moderate to severe recurring
congestion during rush hours and in many cases at other times during
the day and on weekends. This is due to the need for the signals to
service five separate movements per cycle. With an RCUT, by forcing
traffic on the cross streets to
turn right,
this will overlap that traffic with the corresponding left turn from
Bandera and will eliminate the need for discrete green time
for the
left
turn and straight-through movements from those streets, resulting in
just two movements to be serviced per signal cycle. The green time
that would have been needed for the other three 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 wait times and congestion.
If
all of that sounds like technical gibberish, here's another way of
explaining it. At the conventional intersection, drivers who arrive as
the light turns red light have to wait for three or four other
directions to get a green light before their light turns green again.
At an RCUT, drivers only have to wait for one signal change
before they get a green again.
Additionally,
with an RCUT, each half of the intersection operates independently
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.
Modeling
showed that
this configuration is expected to provide good
long-term congestion relief
based on 25-year traffic projections. RCUTs
have also been proven to improve safety. A study for the North Carolina
DOT showed that RCUTs reduced traffic collisions by 46% and decreased
crashes with injuries by 63%. A study of RCUT 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, despite higher traffic volumes in 2021, the number of
crashes was less than half of the number in 2017.
Example Signal Timings
- These charts show an example of the
proportion
of each signal cycle dedicated to each movement (i.e. green time for
that movement.)
- Cycle time for both is equal.
- Up/down arrows
are north/south Bandera Rd.
- Current
timing splits are
approximate as they change during the day, but are typical.
- RCUT
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 an
RCUT, the signals on each side of Bandera Rd. can be timed
independently of the other, so the RCUT chart below combines
both directions for simplicity.
|
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Current
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RCUT
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Flyover and
boulevard proposals
As
with previous flyover proposals, the more recent flyover proposals
generated controversy in Leon Valley. Chief among the concerns of many
leaders and citizens there is that
a
flyover would speed
traffic through the suburb and, it is asserted, would
speed drivers past the businesses along Bandera, thus negatively
affecting
them. These businesses, of course, comprise an outsized portion of that
city's tax base, so their concern is understandable. (Of course,
congestion also negatively impacts those businesses, perhaps even more
than a flyover would. Research shows a 10% reduction in average travel
speeds in a corridor can result in a 20% loss of market area for nearby
businesses.) Additionally, there was great
concern
about the aesthetics of an elevated road, specifically
are that it would be unsightly and create a visual
barrier that would divide the city and negatively impact property
values. There was also angst about the noise
that an
elevated road would generate.
With
the flyover proposal causing consternation, Leon Valley enlisted
the
assistance of UTSA's Center for Urban and Regional Planning Research
and the Institute for Economic Development to look at options for
Bandera that could reduce congestion without the harmful effects. After
researching other
concepts, they developed a
proposal for what is known as a
"multi-way boulevard." As
envisioned, this would be a 10 lane at-grade thoroughfare with
signalized intersections in the same locations as today. The
10 lanes would include three
main through lanes in each direction with two parallel frontage lanes
on each side. The frontage lanes would be built in the area used today
for the drainage culverts on the side of the road and would be physically
separated from the
through lanes by landscaped traffic islands. Just like the
frontage roads along a freeway, the
frontage lanes in this concept would provide access to
adjacent properties and would be
the location for sidewalks, bus stops, and bike lanes. Traffic would
move between the through lanes and
frontage lanes via slip ramps located between
intersections, much like the entrance and exit ramps from access roads
to freeways.
Cross-section of
proposed boulevard concept
There
are several examples of
multi-way boulevards in the US including Queens Blvd. and Ocean Pkwy.
in New York City, Octavia Blvd. in San Francisco, and Bothell Way in
Bothell, Washington. There is even a smaller-scale example here in San
Antonio:
Verano Pkwy. on the Texas A&M-San Antonio campus on the South
Side. All of these examples include on-street parking, however, which
the Bandera proposals would not.
The
report listed the expected
benefits of the boulevard concept as follows:
- By
isolating slower local traffic to the frontage lanes, traffic
in the through
lanes can move faster and more safely.
- With
10 lanes, the corridor would have about 66% more lane capacity than
today.
- The
boulevard would be landscaped with trees and other foliage, making the
corridor more pleasant and inviting especially for
pedestrians and cyclists.
- Because
there are no elevated structures, a boulevard would be much less
obtrusive than an elevated highway, thus minimizing visual and sound
impacts.
While the
flyover proposal
would require about 11 acres of additional right-of-way, the boulevard
proposal would require about 30 acres of additional
right-of-way.
In
addition to traffic, access, and aesthetic considerations, UTSA's
Institute of Economic Development was asked to study the effect an
elevated road might have on property values. Unfortunately,
there's a dearth of direct data on the subject. However, data was
available
on the impact when elevated freeways were torn-down. This data showed
that doing so
resulted in a substantial increase in adjacent property values. Based
on that, UTSA's researchers extrapolated that building an
elevated
expressway through Leon
Valley would result in an equally inverse decrease in property values.
(COMMENTARY: That
seems
to be an overly simplistic inference as there are
many other variables and factors that would likely have played into
those
increases. To be fair, it would require much more extensive study to
identify and control for those factors. But it is also
well-known that improved access typically leads to an increase
in
property values. Furthermore, my own cursory
analysis of several random properties in the shadow of the
current
flyover in the vicinity of Bandera and Wurzbach show that almost all of
them increased in value over a five year window at roughly the
same rate as
other properties further down
Bandera in Leon Valley. Again, to be fair, I was not able to compare
the property values immediately before and after the flyovers were
built nor to do an extensive analysis. In closing, normally I would
present the study's findings without
editorial, but I felt these points needed to made. Your mileage may
vary.)
There is also evidence that increasing the walkability of an
area increases adjacent property values.
UTSA's
researchers admitted that the boulevard proposal, while adding
capacity, is
not likely to solve congestion issues, which TxDOT's subsequent
analysis and modeling confirmed. Instead, it makes improvements
while further considering additional transportation modes, adjacent
land uses, and economic impacts. In conjunction with the boulevard
plan,
UTSA's team also emphasized the need for expansion of other nearby
roadways as well
as the overall road network itself.
As
an interesting footnote, this is not the first time a boulevard plan
has been proposed as an alternative for this general corridor. A
proposal for a
Bandera/Culebra expressway in the 1970s was met by a counter-proposal
from San Antonio Mayor John Gatti for an "avenida", a concept described
as a wide boulevard with bus lanes.
Animation illustrating both the "flyover" and
boulevard proposals.
This is at Bandera
and Huebner looking north.
(Courtesy of UTSA and the City
of Leon Valley)
Renderings
Below are selected renderings created by UTSA of both the
flyover and boulevard proposals. These
renderings are only for illustrative purposes and don't represent any
actual plans. A
sincere thank you goes to the UTSA
Center for Urban and Regional Planning Research and the City of Leon
Valley for making these available.
Bandera and Seneca: Flyover
Bandera and Seneca: Boulevard
Bandera and Seneca: Flyover
Bandera and Seneca: Boulevard
Bandera and Huebner: Flyover
Bandera and Huebner: Boulevard
Bandera and Huebner: Flyover
Bandera and Huebner: Boulevard
Bandera and Eckhert: Flyover
Bandera and Huebner: Boulevard
FAQ
Below are some frequently-asked questions and comments about this
corridor.
- RCUTs looks confusing. They 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 an RCUT, 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. RCUTs also
inherently
improve safety by reducing conflict points (the
point where vehicle paths cross) by half.
Statistics for RCUTs show improved safety. A study for
the
North Carolina DOT showed that RCUTs reduced traffic collisions
by 46% and decreased crashes with injuries by 63%. A study of RCUT
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, despite higher
traffic volumes in 2021, the number of crashes was less than
half of the number in 2017.
- How does this crazy design
(RCUTs) 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 an RCUT works"
section of the main Retricted Crossing U-Turn
intersections page
for a deeper explanation of the RCUT "secret sauce".
- 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 at least 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 RCUTs. 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 will
work with the City of Leon Valley to mitigate concerns with response
times. The initial proposal includes a special traversable median and
actuated traffic signals for emergency vehicles at El Verde.
- Why not build overpasses instead?
Various
flyover plans have been proposed over the years, but the City of Leon
Valley has been and continues to be opposed to such plans. Therefore,
engineers have had to look at alternatives. Across the country, traffic
engineers have
discovered that innovative
intersections like RCUTs can produce good congestion relief and safety
at a fraction of the cost and construction time of flyovers and other
traditional
grade-separated solutions.
- Why are there signals to leave
the RCUT turnarounds?
This is to
prevent slower moving vehicles from entering the faster traffic stream
and causing conflicts that could result in collisions or
congestion.
- Are there any other
RCUTs in San
Antonio?
Yes,
there have been two RCUT 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
approval and funding for freeway expansions was obtained. As intended,
the Loop 1604
RCUT
was replaced by a freeway in 2016, and the US 281 RCUT was replaced by
a freeway in 2021.
An
RCUT intersection was built at Bandera at FM 1560 South in Helotes in
2018, and two more RCUT intersections are under construction in
Helotes. Unlike the 281 and 1604 RCUTs, which were built as
short-term fixes, the RCUTs in
Helotes are considered a long-term
solution.
RCUTs have also been constructed on a segment of
Loop 337 in New Braunfels, and they are planned for Loop 1604 from US
90 to Macdona Lacoste Rd.
- 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, the "superstreet" (RCUT intersections) 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 traffic patterns and expected future traffic volumes on
US 281 exceed what RCUTs can optimally handle, so they
would never have been planned as a permanent solution there. While
projected 2047 traffic volumes on some sections of Bandera are at the
upper end of what RCUTs would typically be expected to handle, modeling
shows that they should still be able to provide substantial congestion
relief, and interim volumes for many years will be in the "sweet spot"
for RCUTs to provide dramatic congestion reduction.
- Who came up with this cockamamie
design? This won't work and is just a waste of money.
The RCUT 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 RCUTs showed appreciable
improvments, and computer modeling shows that these RCUTs will do
the same. An RCUT
is one of several types of "innovative" or "alternative" intersection
designs
being implemented across the country at intersections
where improvements from conventional expansions would be short-lived
but
where conditions do
not warrant more expensive traditional upgrades such as overpasses.
Many people expressed similar skepticism about the nearby
Bandera/1604 displaced left turn (DLT) intersection, but the new design
has substantially
reduced congestion and crashes
there.
- Why can't they just
synchronize the traffic signals on Bandera? This would fix the problem.
Actually, the signals on Bandera are already part of a coordinated
system and are optimized. Many people think that just synchronizing
(coordinating) signals is a magic solution to all congestion. While in
many situations it can and does provide substantial benefits, the fact
is that coordinated signals
can only provide improvements up to the point where traffic volumes on
a road reach the saturation point, and then the laws of physics (space
and time) take over. Bandera well exceeds the saturation level at many
times of the day.
The
way that signal coordination works is by breaking traffic
into groups ("platoons") and moving them through the corridor at a set
speed so that they hit each signal green along the way. The
gaps between platoons are then used to allow green time for
cross-traffic and left turns. When traffic volumes on a
roadway reach saturation, the number of vehicles is greater than a
reasonable amount of green time at each intersection can clear on each
cycle.
Then more vehicles stack up behind those as the gaps
between platoons fill-up with vehicles turning onto Bandera
from
cross streets and driveways. On many urban arterials, the volume of
traffic turning onto and off of a specific roadway at each
intersection often is fairly balanced, so the platoon gaps stay
somewhat stable and therefore signal coordination works better. But the intersecting
road network along the Bandera
Road corridor doesn't allow this and instead forces high volumes of
traffic to turn onto Bandera at one intersection and then
leave Bandera at a downstream intersection (see
the map near the top of this page.) These
"interlopers" consume most
or all of the green time at the next downstream signal that was
intended for the next platoon of through traffic to use. This
results in part or even all of the following platoon getting stopped,
making it
seem like the signals aren't synchronized. With each cycle, the process
repeats and the backups compound.
Here's
another way of explaining it. Imagine the signals on
northbound Bandera at Grissom turn green and about 100
vehicles go
through before it turns red again. We'll
call this "Group 1". As those vehicles approach the Poss intersection,
the signal turns green and stays green long enough allow those 100
vehicles through before turning red again,
and so
on for each intersection downstream. The process repeats then with
Group 2, 3, etc., and everything is good.
Now imagine that after
Group 1 goes through the Eckhert intersection and the light turns green
for Eckhert, 50 vehicles turn onto Bandera. They'll get
stopped at
Mainland when
the light turns red behind Group 1, so there are now 50 vehicles
waiting at Mainland. When the 100 vehicles in Group 2 reach that
intersection, there will then be 150 vehicles wanting to get through,
but
since the signal is timed for a platoon of about 100, the 50 who
arrived earlier from Eckhert will go and
then only about 50 vehicles from Group 2 will make it through, leaving
the last 50
waiting. Then, behind them, 50 more vehicles turn onto Bandera from
Eckhert. That 50, plus the 50 from Group 2 that didn't get through,
means there will then be 100 vehicles waiting at Mainland. Then the
next 100 vehicles
from Group 3 arrive, and now there are 200 vehicles wanting to get
through at Mainland, but only the first 100 (the 50 leftovers from
Group 2 and the 50 from Eckhert) will get through, meaning none from
Group 3 will make
it through.
For those in Group 3, it now seems like the signals aren't
synchronized since they have to stop and wait through a cycle. But it's
not because the signals aren't synchronized that they didn't get
through, it's because additional traffic "stole" their allotted time at
Mainland. And as you can see, with every cycle, those numbers
will keep compounding until the volume of traffic entering the corridor
decreases below capacity.
So
couldn't they just extend the green time at Mainland to account for the
additional vehicles from Eckhert? Sure, up to a point, but not much
because doing so increases the red time on Mainland and for the
southbound left turn, and longer red time of course means additional
delays and
congestion for the drivers on those approaches. And this example was
only demonstrating
how
just one intersection can inject enough traffic to break the
synchronization. Don't forget that even more traffic is going to turn
onto Bandera from Grissom, Poss, Huebner, and the many driveways along
the way, so each subsequent intersection downstream would need to have
progressively more green time to accommodate each additional cohort of
interlopers. This would eventually result in the downstream signals on
Bandera
having to be green constantly or nearly so in order to allow all that
traffic through. That is obviously not a realistic solution.
Alternatively, less
traffic could be allowed through the Grissom intersection to offset the
traffic turning on at Huebner and Eckhert, but that would just cause
even longer
backups there and therefore is also not practical.
This example shows the limitations of signal coordination. When this
situation
happens,
the traditional solution is to upgrade the corridor to a freeway.
However, a freeway is not politically tenable on this corridor and
would require significant new right-of-way.
Thus, non-conventional
solutions are needed.
-
Why did they build the
flyovers at Loop 410? They don't really help and were a waste of money.
As is often the case, this perspective ignores the bigger picture. The
flyovers at Loop 410 take the heaviest traffic movement at that
location and remove it from two already-congested signalized
intersections. While
traffic coming from Loop 410 to Bandera regularly backs-up during the
afternoon rush hour, it does so out of the way of the surface
intersections. More importantly, before the flyovers were built, that
traffic nearly always backed-up onto the Loop 410 mainlanes, which was
a dangerous situation. Now, that traffic is stored safely out of the
way. Meanwhile, traffic headed the other way enjoys a good five minutes
or more of time savings during the morning rush hour. When
Bandera through Leon Valley is improved, commuters going from Loop 410
to Bandera during the afternoon rush hour will enjoy the full potential
benefits of the existing flyover. While congestion at that location may
make it seem like the flyovers don't help, the point that's often
forgotten is this: how much worse would the congestion there be without
the flyovers?
-
The existing flyovers
have caused several nearby businesses to go under.
I am only aware of one business that has claimed it was harmed by the
flyovers. Regardless, there is no objective data (to my knowledge) to
support
that claim. It could have been a case of that business already having
difficulties that were exacerbated by the traffic changes, or,
perhaps, the flyovers are being used as a scapegoat. The other
established businesses in the area seem to be doing fine. Regardless,
congestion is at least equally detrimental to businesses if not more
so, so improvements need to be made. While nobody wants to see
businesses fail, there will, unfortunately, always be trade-offs
whenever a major change is made, and attempts are made to minimize
those
impacts.
-
Traffic has been bad on
Bandera for decades-- why hasn't anything been done?
As mentioned above, several attempts have been made over the years to
improve Bandera, including
adding flyovers at major
intersections and an elevated tollway, but the City of Leon Valley
vetoed all of the proposals due to fears that those plans would hurt
local
businesses, which would have a serious impact on the city. New
leadership in Leon Valley in
recent years has recognized the need for improvements and has indicated
a willingness to find solutions, but there's still a long road ahead
(pun intended.) A new comprehensive planning effort that includes TxDOT
and the cities of Leon Valley and San Antonio is now underway with all parties agreeing to the preferred solution.
Acknowledgments
Special
thanks to
the following for their assistance in providing information about these
proposals:
Additional
information
|
Freeway system
Alt intersections
