Other San
Antonio Area Roads
Restricted
Crossing U-Turn (RCUT) Intersections |
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This
page last updated May 12, 2022 |
A "Restricted
Crossing U-Turn" intersection (RCUT)-- also formerly known as a "superstreet"--
is a divided roadway where the major intersections have been
modified to eliminate left turns and straight-through traffic
on the secondary streets that cross the main roadway, and where minor intersections
are converted to "right-in/right-out", i.e. traffic can only turn right
onto or from those streets. Turnarounds are then provided to
facilitate left turns and crossovers via a U-turn instead.
This configuration improves traffic flow and safety by eliminating most
left turns and cross traffic. At the signalized intersections, doing this reduces the
number of
traffic
signal
phases required to move traffic through the intersections from typically five or
more to just two, thereby
allowing for longer green times for all movements without extending the
overall cycle time, thus reducing wait times and the resulting congestion.
This is one of several "innovative" or "alternative"
intersection types used to improve intersection
throughput when
grade-separation (overpasses or flyovers) is not possible,
not warranted, or too
expensive.
The
San
Antonio area has had four sections of RCUTs: one on US 281
North (four intersections, replaced by freeway upgrade), one
on Loop 1604 West (two
intersections, also replaced by freeway upgrade), one on
Bandera Road (currently one intersection; construction underway on two
more), and Loop 337 in New Braunfels (three intersections.) In the 281 and 1604 cases, the RCUTs were in a transition
area between freeway and non-freeway sections of those
roads,
and both were intended to be short-term improvements while upgrades of those segments to
freeways was stalled due to various legal challenges and funding issues. The 281
and 1604 RCUTs
were the
first two superstreets in Texas.
An
RCUT intersection was completed on Bandera Rd. at FM 1560 South
in 2018. This was the first of several RCUT
intersections
planned for Bandera Rd. from Loop
1604 to
Triana Parkway. Unlike those on US 281 and on Loop 1604, the RCUT plan
on Bandera is considered to be a long-term solution
for
existing and expected congestion. It appears that RCUTs will also be the plan for Bandera between Loop 1604 and Loop 410. Finally, another RCUT section is planned
on Loop 1604 between US 90 and Macdona Lacoste Rd., where it is also intended to
be a long-term solution.
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Please
note that the intersection diagrams below are generalized for the types
of intersections involved and not intended to reflect specific existing
or future conditions. They are intended
instead to illustrate the concepts being discussed. Thanks to
"SPUI"
for the base RCUT intersection illustration used in the intersection
diagrams. |
On this page:
Local RCUT history
US
281
In February 2009, with the proposed US 281 tollway stalled due to
ongoing litigation that resulted in a new environmental study being
required, engineers with Pape-Dawson Engineering made an
unsolicited proposal to the Alamo Regional Mobility Authority (ARMA) to
convert US 281 into a "superstreet" from Encino Rio to
Marshall as a short-term fix while the lawsuits played out and
the new environmental study for the
long-delayed expansion project on 281 was completed. Modeling showed
the superstreet plan could
increase traffic throughput on 281 by 30%, increase average rush hour
speeds by about 10 mph in both
directions, and reduce travel time by about eight minutes between Loop
1604 and Marshall Rd.
The
MPO approved funding for the
project
on March 23rd, 2009. Funding came from a combination of funds
from the federal stimulus, Advanced Transportation District, and City
of San Antonio. On January 14th, 2010, ARMA's board selected
Ballenger Construction's bid of $5.2 million to build the project,
which was nearly 20% below the final estimates and nearly 50% below
initial projections. Ground was broken on the project on
March
11th, 2010.
The
first intersection (Encino Rio) was completed on August
29th, 2010. Weather delayed work on the Marshall Rd. intersection;
it
was finally completed on September 26th. The remaining
intersections were completed on the weekends of October 2nd and 9th.
As planned, the RCUT intersections were subsequently removed when the
corridor was upgraded to a freeway in 2020 and 2021.
Loop
1604
In October 2009, with plans for the US 281 RCUTs nearing
completion, the Bexar County Commissioners Court approved funding to
study a possible RCUT section in the Loop 1604 West corridor,
specifically between Braun Rd. and SH 151, as a possible interim
solution to ease congestion there while ARMA completed an environmental
study
for an expansion. The superstreet study,
completed in early 2010, showed that a combination of conventional
improvements (mainly additional through lanes at Braun) and RCUT
intersections
along that section of 1604 would provide substantial
improvements.
In
May 2010, ARMA previewed the initial designs and
expected benefits. Under the plan, the intersections of New
Guilbeau and Shaenfield would be reconstructed as RCUT
intersections. It was estimated that by doing so, travel
speeds
could be increased by 36% and delays reduced by 69% during the morning
peak and that average travel speeds could be increased by 65% and
delays reduced by 79% during the evening peak period.
The
project began
construction in March 2011. The New Guilbeau intersection was
completed August 18th, followed on September 15th by the Shaenfield
intersection. As intended, the RCUT intersections were subsequently
removed
when the corridor was upgraded to a freeway in 2016.
In
2022, earlier plans for an expansion of Loop 1604 West from US 90 to
Macdona Lacoste Rd. to a divided highway were updated to include
a full RCUT configuration. Construction is expected to start in
late 2024.
Bandera Road
TxDOT has proposed two RCUT segments along Bandera Rd.
One
is through Helotes from Loop 1604 to Triana Parkway. Construction on
the first intersection-- at FM 1560 South-- was completed in October
2018.
This intersection was the
first to be done because a project was already in the works to
reconfigure the obsolete and congested dogleg intersection at Circle A
Trail, so the RCUT
design was incorporated into that project so that the new intersection
wouldn't have to be torn-out and redone when the rest of the RCUT
corridor is built in the future.
The
next section-- from Loop 1604 to FM 1560--
is currently under construction with completion set for early 2024. The
remaining intersections from FM
1560 to Triana are currently
unfunded and
therefore there is currently no timeline for their completion.
The
second proposed segment for Bandera Rd. was
between Loop 410 and
Loop 1604, but was
shelved after Leon
Valley declined to endorse it. However, an RCUT corridor is now the
recommended alternative after other
proposals were studied. Leon Valley has endorsed
it this time around. There is currently no funding or timeline for its
implementation.
Loop 337 (New Braunfels)
Work
was completed in 2021 to expand a section of Loop 337 in New Braunfels
from SH46 West to River Road to a
four lane divided highway with RCUT intersections.
Conventional
intersection operation
Before
explaining
how an RCUT works, it's important to understand
how conventional intersections function, especially
with regards to the traffic signal operation. Understanding
the signal phasing is vital to grasping the improvements
provided by an RCUT.

What is a signal phase?
A signal
"phase" is the green time assigned to a specified movement or
collection of
movements in a traffic signal cycle. In other words, when the signal is
green for a specific movement (straight through, left turn, etc.),
that's a signal phase. When it changes to red and another movement gets
a green signal, that's another phase. The complete rotation through of
all of the phases is a cycle.
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This
is how a typical conventional intersection is configured; the road going left-to-right is the main road:

The
"split-phase"
signal configuration typically necessitated by traffic patterns at
these
intersections requires five signal phases (i.e. signal changes) per
cycle (or three phases for "T"
intersections) to allow for each movement through the intersection:
Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

So, if you get stopped just as the light is turning red, you
have to wait for three or four other directions to have a green light
before you get to go. Some
signal plans can even have as many as eight phases per cycle!
In
a congested
intersection, the
number of phases
and the required length of each phase due to heavy traffic
volumes
causes overall signal cycles to be long, thus causing long
queues and congestion, especially during peak periods. Additionally,
each signal phase adds up to 10 or so seconds of "lost" time
due to yellow and all-way red clearance intervals as well as the time
it takes for stopped motorists to react to a green and to start moving.
Many
times, people will say that the signal timings simply need to be
adjusted in order to reduce the congestion. In some cases, signal
timings can be further optimized to improve conditions. However, in
most cases, signals are already optimized as much as they can be, and
the laws of physics prevent any further efficiency of the existing
intersection. When this happens, the intersection must be physically
changed.
How
an RCUT works
An
RCUT
reconfigures intersections like this:

At
first glance, this can seem quite complicated, but it actually makes
sense once you
understand how it works and why.
An
RCUT intersection eliminates the
ability of traffic on the cross street to continue straight through the
intersection or to turn left ("restricted crossing".) Instead, all
traffic on the cross street
must turn right onto the main road, then use a downstream
turnaround ("U-Turn") to either go the opposite direction or to return
to the
cross street to continue on it. Those turnarounds are
typically located
approximately 1000 feet (about 2/10th of a mile) from the intersection
they serve to allow sufficient room for merging and storage.
So
how does this help? By
eliminating the through-traffic and left-turns from the cross
streets, the signal phases required for those movements can
also
be eliminated (or, more specifically, they're combined with the phase
for traffic turning left from the main road onto the cross street.) It is by
eliminating
those signal
phases that the benefit is derived (keep reading.)
While
RCUTs in areas with low traffic volumes can operate fine with
stop or yield signs, most RCUTs (including all those in San
Antonio to date) are signalized, and, in fact, it actually
doubles
the number of signals in each direction. Yes, it
seems counterintuitive that adding
signals can help improve traffic flow. But it's not the number of
signals that causes problems; it's the time required to service each
movement at the intersection that causes backups. By
eliminating
the straight-through and left turn movements on the cross street,
the number of signal phases (green time for a movement)
is reduced
from the previous five phases to just two (or from
three to two
at "T" intersections):
Phase 1

Phase 2

That's
it-- just two signal phases! Notice
how many
movements are accomplished in the second phase. This
essentially
takes phases 4 and 5 and the left turn movements of phases 1 and 3 of
the conventional intersection discussed above and combines them all
into one,
eliminating all the time required for those individual
phases.
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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 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. Drivers
then needing to use the turnaround may have to subsequently wait for
one more signal change, but that's still less than before. |
Furthermore,
significant additional time savings is
realized because every signal phase inherently includes some "wasted"
time in the form of the yellow and all-way red clearance intervals as well
as the time it takes for drivers to start moving when they get a green
light. All of that can add 5-10 seconds of lost time per
phase.
All
of these time savings allow the green time for through traffic on
the main road to be increased without having to correspondingly
reduce the green time for the cross street or lengthen the total cycle
time.
It
should be noted at this point that the diagrams above for the RCUT
signal phases are simplified to
show the corresponding phases on both sides of the main road operating
simultaneously in order to show the overall concept. But in practice, the phases
are usually staggered to better coordinate traffic through the
intersections and to optimize the operation of each signal based on the
traffic volumes at that time and location.
RCUT "secret sauce"
further explained
If the explanation above is still a bit muddy, here's another way of
looking at it. Imagine in the
diagrams above that you're on the main road headed from left to
right. You reach the conventional
intersection just as the light turns red (phase 3.) You then
have
to wait through phase 3 for 20 seconds, phase 4 for 30 seconds, and
phase 5 also for 30 seconds before you get a green light again on phase
1, for a total wait time of 80 seconds. With the RCUT, all of the
movements that took 80 seconds before can now move at
once and therefore be accomplished
in a
single 30 second
phase, which means that through traffic on the main road is now only
stopped
for 30 seconds per cycle instead of 80 seconds. The 50 seconds
of time that's
been freed-up by eliminating two phases can be added
to the green time for the main road. So
if
through traffic previously was allocated 40 seconds of green
time, it can get 90
seconds with the RCUT without
any change to
the overall two minute cycle time. This
an
obvious and substantial improvement and is where the benefit of a RCUT
is derived. See below for a
graphic visualization of these timings.
(Note that the
timings I
provide
here are for illustrative purposes only and do not necessarily reflect
any specific actual current or previous phase and cycle times.)
Example
timings
Illustrative
red and green signal times and associated movements from the
perspective of
through traffic on the main road moving left to right in the
diagrams above.
(Be sure to read the explanation in the paragraph above.)
Note that the
30 seconds for the cross street in the RCUT could then be increased to
further reduce
congestion on those approaches if necessary and still leave significantly more green time for
the main road
than it would have in
a conventional intersection. For example, the cross street could be
allocated 40 seconds of green time, leaving 80 seconds for the main
road, which is still twice as much as it had before. This demonstrates
the additional flexibility afforded by this design.
Here
is yet another way of looking at it:
Example
Bandera-Hausman/Leslie
Signal Timings
- The whole pie below represents
the time for a full signal cycle (~150 seconds.)
- The pieces of the pie show the
proportion of green time each movement gets during each cycle.
- Left/right arrows represent the main road (Bandera Rd. in this case.)
- With
an RCUT, all the movements except the through movements on the main road get
combined, and in this example, are combined into the biggest piece of
the pie from the conventional intersection. After
doing so, that slice can (and probably would) be increased as needed to
reduce congestion on the secondary street (Hausman/Leslie in this
case), and even after doing so, everyone
still gets more green time than they had in the conventional
intersection.
- Current
timing splits are
approximate as they change during the day, but are typical.
- Timings
were obtained by yours truly by monitoring the Bandera-Hausman/Leslie intersection for three
half-hour periods during a Wednesday in April 2022.
- Finally, in an
RCUT, the signals on each side of the main road can be timed
independently of the other and, thus, would be two separate pies, so
the RCUT chart below combines
both directions for simplicity.
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Current (conventional)
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RCUT
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Better synchronization
In
addition to reducing signal phases, RCUTs allow for much
better synchronization of the signals. With conventional
intersections, signals along a corridor in both directions are
inherently
inter-dependent-- in other words, changes cannot be made to one
direction without affecting the other. This
dependency makes signal coordination and signal progression (or
"synchronization") tricky, especially two-way progression. But with an
RCUT, all the movements on one side of the intersection
don't affect the other side at all, so the signals for traffic going in
one direction on the main roadway are
completely independent of those
for the other direction. In effect, each side of the main road
functions like an independent one-way street. This
provides the ability to coordinate the signals much more easily and
reliably without regards to the number of signals or their spacing, and
the signals can react better to the traffic conditions on their side of
the road.
Essentially, it provides the optimal environment for signal
coordination.
Traffic
flow through the intersections
While
some of the movements through an RCUT intersection are the same
as a conventional intersection, some are quite different and a bit
unintuitive. Below are diagrams depicting the various routes through an
RCUT intersection.
Straight-through
traffic on the main road and traffic turning right onto the cross
street works just like a conventional intersection:

Traffic
turning
left from the main road to the cross street also works just like a
conventional intersection:

And
traffic
turning right onto the main road from the cross street works just
like a
conventional intersection:

However,
traffic wanting to turn left from the cross street onto the main
road
instead turns right, then uses the downstream turnaround to head the
other direction:

Similarly,
traffic wanting to continue straight on the cross street across the
main road instead has to turn right, use the downstream turnaround,
then
turn right again to get back onto the cross street:

Right on red
prohibition
Although not required to make an RCUT
function, RCUTs
in San Antonio typically employ a right-on-red prohibition
from
the
cross street. The reason why is two-fold and has to do with the fact
that, at an RCUT intersection, many of the vehicles turning
right will then subsequently be
making a U-turn. Doing this requires them to cross the through traffic
lanes. Since a
vehicle that makes a right turn on red will be traveling
substantially slower
than the through traffic and doesn't have a lot of space to get up to
speed before merging over, those drivers can create
a significant safety hazard as they cross the through traffic lanes.
Even if there isn't a collision, vehicles in the through lanes must
slow down when encountering someone cutting across to the turnaround;
in heavy traffic conditions, this can be the genesis of congestion.
Also,
restricting when vehicles can cross helps to create a
"platoon" of
vehicles when the light turns green. When signals are coordinated, they
are timed to more
efficiently move platoons of vehicles, so vehicles crossing
over
individually
while the light is red often won't get that benefit
(i.e. still have to
wait for the signal at the turnaround anyway.) Yes, this does
inconvenience
drivers who just want to turn right and not make the U-turn,
but since it's difficult
to provide
separate regulations for each movement in this situation, the
one
that provides the greatest overall benefit is usually
employed.
On
US 281, an exception to the no turn on red was made for
the
far right lane at Stone Oak because there was an added lane on
southbound 281 at that location, and the traffic in that lane is
typically not
headed for the turnaround. An additional exception was made
for
the far right lane at Evans. On Bandera Rd., exceptions were made for
Circle A Trail due to the low traffic volumes there.
RCUT
concerns and complaints
- It's
too
confusing for drivers and will causes more accidents:
This is
always one of the first visceral 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 inherently
improve safety by reducing conflict points (the
point where vehicle paths cross) by half. And 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 crashes decreased
40% in the first nine months the DLT was in operation, and the number
of crashes in 2021 was less than half of those in 2016 and 2017 before
construction began, despite equivalent traffic volumes.
- It
won't be easy or safe to cross over to the turnarounds or turn from the
turnaround:
A question often posed by people unfamiliar with RCUTs is how
traffic from the cross streets can safely merge onto the main road,
then move across the traffic lanes to the turnaround, then
merge back into the other direction. The answer is that there
are
signals that stop the through traffic on the main road to allow that
cross street traffic out at both the main intersection and also again
at the
turnarounds. As discussed above, even though the signals at
the
main intersections remain and extra signals are added at the
turnarounds, the number of signal phases for all the signals is reduced
substantially, thus
allowing significantly more green time for the main road through
traffic and
signal synchronization is much easier.
- It
requires
traveling the wrong way/out of the way:
Some folks understandably are bothered that to
turn left
or go straight on the cross street requires going out of one's way to
accomplish. This is true and will always be perceived as an
inconvenience by many drivers, but because wait times are shorter and
overall congestion in
the
area is reduced, travel time through the intersection is still
usually shorter 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.
- Pedestrian
crossings:
Finally, some people have wondered how pedestrians
are
able to cross these intersections. Below is a diagram of the
typical pedestrian crosswalks and pathways in an RCUT
intersection, all controlled by signals. Crossing the main road here
is a bit safer than a conventional intersection because it is actually
two much shorter crossings.

How an RCUT
differs from a "Michigan Left"
People
who have
lived in Michigan and other parts of the country may be familiar with
an intersection layout known as a "Michigan Left", also known as a
"Median U-Turn or "MUT", and some have
proffered that an RCUT is the same thing just with a different
name. However, while a Michigan Left is similar to a RCUT,
there are some significant differences between the two:
- In
a Michigan
Left, there are no left turns at all. All left turns from
both
the main road and cross street are made using the
turnarounds. In an RCUT, traffic can make left turns from the main road
onto the cross street, but left turns from the cross street are made
using the turnarounds.
- In
a Michigan
Left, traffic on the cross street can go straight through. In
an RCUT, all traffic on the cross street must turn right onto the main
road. Straight-through traffic on the cross street
must
use the turnaround to return to the intersection, then make a right
turn at the intersection to continue in their original direction.
Below
are
simplified schematics that show the allowed maneuvers in each type of
intersection:
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RCUT traffic flow |
Michigan Left
traffic flow |
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Local RCUT
results
US 281
To
objectively
measure whether the US 281 RCUT had the intended
results,
engineers did before-and-after measurements of travel times, average
speeds,
and traffic volumes. The study found that after the
completion of
the RCUT, travel times were notably reduced and average speeds
increased even though overall traffic volumes increased in the
corridor. The table below summarizes the findings. To
ensure an "apples-to-apples" comparison, data was collected for
Tuesday-Thursday periods when school was in session and when there were
no abnormal incidents in the corridor (e.g. accidents, signal
malfunctions, bad weather, etc.)
Metric |
Before RCUT |
After RCUT |
Southbound
travel time
(Bulverde to Loop 1604, morning rush hour) |
23.3 minutes |
19.2 minutes |
Southbound
average speed
(morning rush hour) |
16 mph |
19 mph |
Northbound
travel time
(Loop 1604 to Bulverde, evening rush hour) |
19.2 minutes |
12.7 minutes |
Northbound
average speed
(evening rush hour) |
19 mph |
29 mph |
Traffic
count (north of Evans) |
60,100 vehicles/day |
63,552 vehicles/day |
Traffic
count (south of Evans) |
74,000 vehicles/day |
81,526 vehicles/day |
Anecdotal
reports for the
first few weeks
from motorists in the corridor on Facebook, from media reports, and
comments on various websites indicated that most of the time, the RCUTs
provided some relief. Recurring traffic
signal
malfunctions for the first month or so after completion of the
project did cause some initial problems; those were later attributed to
the fact that the signal controllers used for the project were a new
model and the issues were resolved with assistance from the traffic
signal equipment vendor.
Furthermore,
because of their ability to better handle traffic, the RCUTs were kept
during construction to upgrade US 281 to a freeway.
Loop 1604
Over
on Loop
1604, a
before-and-after study showed a reduction in peak period travel time of
35% southbound and 14% northbound. The primary reason for the
significant discrepancy between northbound
and southbound benefits was likely caused by an increase in
traffic (induced or latent demand) drawn by the
improved conditions of the RCUTs exceeding the capacity of the
ancillary
improvements made
at the Braun intersection. This caused traffic to back up at the Braun
intersection and cut into the travel time improvements of the RCUTs.
Anecdotally, the Loop 1604 superstreet had a more profound reduction in
congestion than the one on US 281 due to the lower traffic volumes on
Loop 1604. The most glaring example of the improvement was on weekends.
Before the superstreet, the entire segment from Braun to
Shaenfield was typically congested in both directions most
of Saturday and Sunday afternoon; after the superstreet, there
was no congestion on that segment.
Other
sites of interest
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