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Traffic Intersections Gaining Speed

BALTIMORE (Ivanhoe Newswire) -- Wherever you drive, chances are you end up sitting in traffic -- and it's not just on highways. Congested intersections nationwide are on the rise and getting worse. As a result, better intersection designs are gaining speed all over the country.

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Drivers know the routine: Stop. Wait for the light. Go on green, and then repeat at the next intersection. Idling engines waste 2.3 billion gallons of fuel annually. Now, engineers at the University of Maryland's Traffic Safety and Operations lab are studying transportation and traffic to help pick up the pace with unconventional intersection designs.

"What we try to do is minimize the delay, and one of the things you do to minimize delay is reduce the number of traffic signal phases at the intersection," Saed Rahwanji, M.S., a traffic engineer at the Maryland State Highway Administration in Baltimore, told Ivanhoe.

A big problem at intersections is left turns. Reconfiguring the turns can reduce a major source of congestion.

"All the designs share the common feature -- try to separate the left turn from the through traffic volume," Gang-Len Chang, Ph.D., a transportation engineer at the University of Maryland in Baltimore, told Ivanhoe.

In a continuous flow design, left-turning vehicles begin to turn several hundred feet prior to the main intersection. Then, they turn at a signal with a "crossover" move into new lanes to the right of the opposing traffic.

"That could be beneficial in an area … with a lot of traffic," Dr. Rahwanji said.

In the median U-turn style, no left turns are allowed. Drivers travel past the road they intend to turn onto, make a u-turn at a designated lane with a median. Then after that turn, they return to the light and turn right.

"Sometimes when you look at these designs from a plan view, you think about it as a complicated, complex maneuver, but as a driver, you're only driving one approach -- you want to make a left turn," Dr. Rahwanji said. "You follow the sign."

Some designs are being used now on roads and can be cost-effective solutions for crowded intersections … and headache relievers for drivers.

There are many other unconventional intersection designs like the jughandle, the continuous green-T, the superstreet and the bowtie. Some designs are used at less congested intersections.

The Institute of Electrical and Electronics Engineers, Inc.-USA, the Institute for Operations Research and the Management Sciences and the American Society of Civil Engineers contributed to the information contained in the TV portion of this report.

Click here to Go Inside This Science or contact:

Gang-Len Chang, PhD
College Park, MD 20742
(301) 405-1953

Institute of Electrical and Electronics Engineers, Inc.
Pender McCarter


Institute for Operations Research and the Management Sciences
Barry List
(443) 757-3560

The American Society of Civil Engineers
Joan Buhrman
Reston, VA 20191-4400
(703) 295-6404

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