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Alternative Intersections: Displaced Left Turns - YouTube
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today our communities face a growing
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number of transportation challenges as
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traffic volumes grow and congestion
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worsens motorists pedestrians and
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cyclists confront greater risks at
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intersections we need balanced solutions
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that improve safety and keep people
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moving at the federal highway
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administration our first priority is
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safety and our mission is to improve
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mobility for all users of our nation's
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highways in support of these goals we've
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been evaluating innovative intersection
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designs for many years alternative
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intersections are are worth considering
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because they deliver more for less they
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get more cars through the same spaces
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than a conventional intersection and
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they deliver better safety than a
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conventional intersection where they
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have been built travelers save time
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agencies save money and communities
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benefit from safer facilities one
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innovative intersection design the
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displaced left turn intersection
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implements unopposed left turns at
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intersections by crossing traffic over
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to the other side of the road in advance
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at many intersections the critical
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question is how to address left turns
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how they are treated has an impact on
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the efficiency of the intersection and
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can reduce a crash type that tends to be
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quite severe the displaced left turn
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design also known as the continuous flow
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intersection or CFI moves the left turn
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crossover upstream drivers cross over to
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the left side of the road into an
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exclusive left turn lane
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as they enter the primary intersection
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the left turns proceed unopposed
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compared to a conventional intersection
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conflicts are fewer at a DLT an
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important step to improving intersection
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safety conflict points are reduced from
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32 for a conventional intersection to 28
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for a full DLT additionally the DLT
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design allows left turning traffic to
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move simultaneously with through traffic
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resulting in significant operational
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benefits studies show this increases
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capacity as much as 70 percent the big
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outstanding benefit is capacity signs
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and pavement markings inform and guide
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drivers as they approach a displaced
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left turn intersection traffic signals
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are easily synchronized resulting in
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improved efficiency a DL T is terrific
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for signal timing it allows us to reduce
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the cycle length so reduces the read
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time for everybody so we're able to
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reduce cycles establish good progression
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individual signals within the DLT are
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easy to coordinate with each other so
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from a driver point of view most all
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drivers would only have to stop once if
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at all pedestrian crossings that a
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displaced left turn intersection are
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similar to a conventional intersection
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pedestrian signals are provided ensuring
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adequate crossing opportunity and time
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an added benefit is the raised
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channelization needed to separate
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traffic these islands can also serve as
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a refuge for pedestrians resulting in
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shorter simpler crossing stages the
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displaced left turn is also very
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adaptable a full D LT may be appropriate
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for an intersection of two high-volume
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arterial roads each with high volume
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left turns
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a DLT can also be partial limited only
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to the approaches where needed this
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makes it well suited for busy
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t-intersections finally because the
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capacity of the DLT is much higher than
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a conventional intersection it can
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postpone or eliminate the need for a
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full interchange making it a
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cost-effective option intersection is a
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treatment that can be very effective
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don't be afraid of diverting movements
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slightly away from the intersection
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because you can't just keep building
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through lanes to save 10-15 seconds you
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really want to synchronize the movements
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the federal highway administration
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encourages communities and agencies to
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consider the displaced left turn to
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improve the safety and efficiency of
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existing intersections as well as an
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option for new intersections for more
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information about the displaced left
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turn and other innovative intersection
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designs please visit safety.fhwa.dot.gov
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you
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