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