San
Antonio Area Freeway System
PROJECT
INFO:
Wurzbach Pkwy at NW Military |
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This
page last updated March 15, 2022 |
Location
Wurzbach Pkwy from Bluffton Oaks to Elm Creek
Status
Completed
Timeline
Construction started in August 2020 and is complete.
Description
This project made improvements the Wurzbach Parkway
intersections
at NW
Military Hwy. and Lockhill-Selma Rd.
At
NW Military, the project added
a second dedicated left turn lane and converted the existing
optional left/through lane to a dedicated through lane on all
approaches (i.e. all four approaches now have two dedicated left turn
lanes and three through lanes.) All of
the
left turn
movements have been configured to allow for simultaneous opposing left
turns. A second right
turn lane from westbound Wurzbach to northbound NW Military has been
added, and the
signals are being optimized for the new configuration.
The
eastbound to westbound turnaround on Wurzbach Pkwy. has been moved
slightly further to the west to better accommodate the expanded left
turn lanes from northbound NW Military.
Between
NW Military and Lockhill-Selma, a third westbound lane has been added
and the pedestrian path in the center median has been removed.
At
Lockhill-Selma, an additional through lane for Wurzbach has been added
in both directions. The right
westbound through lane has become a right-turn-only lane at
Elm
Creek (i.e. through traffic has to merge to the left to continue
on Wurzbach.)
A
signal on NW Military at Turnberry Way/Fairfield Bend Dr. was studied
but ultimately not included in the final plan. Engineers will monitor
the area after the project is complete.
A
previous proposal to build an underpass for Wurzbach at NW Military and
a SPUI intersection was cancelled after public feedback (see history
section below for more details.)
How
this project will help
The additional lanes will
provide additional capacity for turns and through traffic.
At
NW Military,
re-orienting the left turn movements to allow for simultaneous
operation allows the left turns to be handled separately from the
through
movements. This will facilitate significantly more efficient
signal operation
because
left turn green time can be terminated when the queue has emptied, thus
allowing for additional green time for opposing through traffic without
increasing the overall cycle length. The previous intersection configuration and its inherent four-way signal
operation did not permit this, which caused very inefficient and
"unbalanced" signal operation that was the primary cause of
recurring congestion.
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.

History
Planners
always evaluate multiple options for any
project to determine which alternative best addresses the need at the
most reasonable cost. Normally, I don't present all the options studied
for a project. For this project, however, I will because the initial
preferred option was scuttled by opposition from
adjacent neighborhoods, resulting in an alternate-- and likely less
effective
in the long-term-- option being eventually selected after an extended
public-involvement
process (and almost certainly some behind-the-scenes political muscling
due to certain prominent nearby residents.)
The
original proposal presented to the public in 2016 was for a Single
Point Urban
Interchange (SPUI) at the
NW Military intersection.
This option would have built an underpass
for through traffic on Wurzbach and would have configured the
surface-level intersection as a SPUI. The primary opposition to this
plan was that through traffic would not be possible on the new
access roads that would be created along Wurzbach Parkway. There is
little need for through access roads at this
location since the adjacent neighborhoods and shopping center have
direct access onto NW Military, which facilitates any movements that
would be lost by blocking through traffic on the access roads at NW
Military. But
residents in the adjacent neighborhood deemed that too inconvenient,
preferring instead to maintain their existing travel patterns at this
intersection via their neighborhood access points on Wurzbach. (In
hindsight, those access points should never have been built. They were
provided in exchange for right-of-way donation for Wurzbach. Once access is given,
it's much harder to take away later.)
Given
that, and an assortment of other objections posed by constituents
regarding trees, downstream impacts at Lockhill-Selma, and
various temporary construction impacts, TxDOT
re-opened the evaluation process and proffered a smorgasbord of options
for public consideration including several alternative intersection designs. After
several stakeholder meetings with the nearby HOAs
and
residents, as well as the general public, the
less-ambitious conventional
improvements plan-- with some additional modifications-- was
finally selected.
That
said, the option that was finally chosen does offer good short to
mid-term improvement, especially for the cost. It is not likely,
however, to provide durable benefits in the long-term.
The
options evaluated are listed below. A brief description along with an
expected benefit rating (one to four "+" signs with four
indicating the
best overall improvement for traffic) and cost rating (one to
four "$" signs with four indicating the highest relative cost)
are
included for each. The projects are ordered generally from highest
benefit to
lowest. All of the options included identical changes to the
Lockhill-Selma intersection, and those were included in the final plan.
- Single Point Urban Interchange
(SPUI) [ ++++ | $$$$ ]
As mentioned above, this was the original proposal for
this project. An underpass for Wurzbach would have been
built with exit and entrance ramps for NW Military. The signalized
intersection on NW Military would have been configured as a SPUI with
no through traffic on the Wurzbach access roads. For information on how
a SPUI works and its benefits,
see the alternative
intersections page.

- Modified SPUI [ +++
| $$$$
]
This is the same as the SPUI proposal above but with
through lanes included on the access roads. Doing this decreases the
signal efficiency since it requires an additional phase per cycle. With
the same cost as a regular SPUI, the decreased efficiency of the
signals caused the cost/benefit ratio for this option
to drop appreciably.

- Diverging Diamond Interchange
(DDI)
[ +++ |
$$$ ]
This option is similar to the SPUI option above but
would
have built a Diverging Diamond Interchange (DDI), similar to the one
currently under construction at Blanco at Loop 1604, instead of a SPUI. As with
the SPUI proposal, there would have been an underpass for Wurzbach Parkway and
no through traffic on the Wurzbach access roads. For
information on how a DDI works and its benefits, see the alternative intersections
page.

- Conventional diamond
interchange/full underpass [ +++ |
$$$ ]
This plan
would have built an underpass for
Wurzbach through traffic and a conventional diamond interchange, i.e.
the standard freeway/access road type interchange found everywhere.
The four-phase signal operation for this type of interchange
is
the same as what is
there today, but the decrease in traffic on the Wurzbach approaches
provided by the underpass was
still not enough to make this the most efficient option, especially
given the cost.

- Conventional diamond
interchange/partial underpass
[ ++ |
$$ ]
This is the same plan as above except that only
eastbound Wurzbach would have an underpass; westbound Wurzbach traffic
would still go through the signalized intersection. This option was
included to compare the impact on traffic at
Lockhill-Selma against the
previous option. While it did decrease congestion there (because
westbound traffic is "metered" here), it resulted in a very imbalanced
signal operation here, which made it much less effective.

- Displaced Left Turn (DLT)
[ ++ |
$$ ]
This option would have built a displaced left turn intersection similar
to the one at Bandera and Loop 1604. Left turns from Wurzbach to NW
Military would shift to the opposite side of the road upstream of the
intersection. The through lanes on Wurzbach would be squeezed together
in the existing median area to provide room for those left turn lanes. There
would be no underpass in this plan. For
information on how a DLT works and its benefits, see the alternative intersections
page.

- Median U-Turn (MUT, aka a
"Michigan Left")
[ + | $ ]
This proposal would have eliminated left turns in all directions at the
NW Military intersection. Instead, left-turning traffic would use new
turnarounds
constructed downstream on Wurzbach. This is known
as a "Michigan Left" intersection and is
similar to the
Restricted Crossing U-Turn (RCUT) intersections built in recent years
at several locations
around the area except that through traffic would be
allowed on both Wurzbach and on Military. By
eliminating left turns, the signals operate with just two phases, the
most efficient operation available. For
information on how a MUT works and its benefits, see the alternative intersections
page.

- Conventional intersection
improvements [ + | $ ]
This option
only makes conventional improvements to the existing at-grade
intersection; it does not include an underpass. The plan shown below is
an early version of the plan that
was finally selected. This plan differs from the final proposal
in the way it handles left turns from NW Military onto Wurzbach. In
this plan, the intersection was not configured to allow for
simultaneous left turns from NW Military, which reduces intersection
efficiency. The final
plan adds a second dedicated left turn lane for each direction of NW
Military and utilizes the left turning configuration of a SPUI, thus
allowing simultaneous left turns and wringing the most possible
efficiency out of this plan. This proposal also adds a third through
lane to both directions of Wurzbach, extends the right turn lanes, and
adds a second right turn lane from westbound Wurzbach to northbound NW
Military; these elements were all included in the final plan.

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