20181598_Att. 20 - Regional Transportation Allian_20160222

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Attachment 20
Synchronized Streets
(Superstreets)
Communities and transportation professionals strive to promote smooth and efficient travel flow that
helps drivers along a street or corridor keep moving while providing safe access to and from various
locations along the street for drivers and pedestrians.
Most delays to drivers and pedestrians along a street or corridor occur at signalized intersections, and
multiple turn arrows or left turn phases can exacerbate those delays by reducing the amount of time
during a signal cycle available for both through travel and other movements.
"Synchronized Streets" can dramatically improve
travel by allowing simultaneous coordination of both
travel directions at all times of day - while providing
reasonable access to side streets with signal control.
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A Synchronized Street is sometimes known by different names - such as Superstreet, J-turn, Restricted
Crossing U-turn, Reduced Conflict Intersection and Alternative Intersection - but the end result is the
same: smoother traffic flow, fewer collisions, and a more efficient use of public roadways.
Synchronized Streets - improving travel flow and safety by redirecting side street travel
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Examples of how side street travelers can cross or turn left at a Synchronized Street
How do they work?
If a driver is approaching a Synchronized Street from a side street, he or she can't go straight
across or turn left in front of approaching traffic. Instead, the driver will first turn right onto the
Synchronized Street and then make a U-turn at a designated median opening a little further
downstream. In general, the overall delay caused by a traditional signalized intersection is much
greater than the delay associated with Synchronized Streets, even with the additional travel
distance, thanks to the reduction in the number of signal phases.
Why do they work?
At a traditional intersection, a side street driver must look in both directions to cross a divided
highway, and there are more threats to a left-turning driver. Conversely, a driver waiting to cross
a Synchronized Street from a side street only needs to focus on one direction of traffic at a time.
Synchronized Streets reduce the number of conflict points, which reduces the risk of severe right-
angle ("T-bone") crashes, especially for side-street drivers desiring to turn left or cross all lanes.
Where can they work?
The Synchronized Street design is well suited for urban or suburban areas with many traffic signals
by enabling efficient coordination in both directions. In addition, the design can be applied to
lower volume rural areas without signals, with through travel free-flow rather than synchronized.
letsgetmoving.org/i40partnership
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Synchronized Streets (Superstreets), continved
Benefits of a Synchronized Street intersection or corridor
• High capacity - As shown in the FHWA chart at right,
Synchronized Streets can serve large traffic
demands for a given number of lanes.
• Improved coordination - The simpler, two-phase
signals on either side of the major street are easy to
coordinate at any speed or any intersection
spacing with a Synchronized Street.
• Reduced delay along the main street - Fewer signal
phases, shorter cycle lengths, and coordinated
operation result in reduced through travel times
along the Synchronized Street.
• Reduced delay along the side street- While side
street movements are indirect, the lower number of
signal phases and shorter cycle lengths often result
in delays comparable to or lower than traditional
intersections, especially during peak periods.
• Flexible operation - Different signal cycle lengths
and speeds are possible for both travel directions,
and signal timing can vary throughout the day.
• Potential to further reduce delays - While flashing
yellow arrow (FYA) is not required for a Synchronized
Street, FYA can further reduce overall delays.
• Safer for vehicle travelers - Studies show a 60
percent reduction in fatal and injury crashes and a
42 percent reduction in all reported crashes
compared with traditional intersections.
• And, safer for pedestrians - Synchronized Streets
provide for a safer and easier crossing of the street.
Synchronized Streets capacity (see FHWA chart aboveJ
Courfesy Federal Highway Administration (FHWAJ
• Four lane Synchronized Streets - can serve through volumes of 40,000 - 50,000 vehicles/day
• Six lane Synchronized Streets - can serve through volumes of 60,000 - 80,000 vehicles/day
• Eight lane Synchronized Streets - can serve through volumes of 80,000 - 100,000 vehicles/day
For the lower range of Synchronized Street volumes, side streets can approach 25,000 vehicles/day;
upper ranges of Synchronized Street volumes need lower side street demands for efficient operation
Examples of Synchronized Streets in North Carolina
• Portions of NC 55 Bypass in Holly Sprinas, US 17 near Wilmington, and US 15-501 in Chapel Hill use
Synchronized Street intersections with simultaneous signal coordination in both travel directions.
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;yncl�ror��izeci ��i� cei intersections along NC 55 Bypass in Holly Springs and U.S. Highway 17 in Leland
For more information about Synchronized Streets:
J. Kevin Lacy, PE, NCDOT State Traffic Engineer, jklacvl @ncdot.aov, 919.773-2800
Meredith McDiarmid, PE, NCDOT State Systems Operations Engineer, [e-mail], 919.825.2619
Joe Milazzo II, PE, Regional Transportation Alliance Executive Director, [e-mail], 919.664.7065
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