Going offbeat

ITE notes unconventional intersection designs

Blog Entry August 20, 2012
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One of the more interesting topics discussed at last week’s Institute of Transportation Engineers (ITE) Annual Meeting was unconventional intersection designs. This is also a field where an engineer might exercise some engineering judgment, which was another session topic.


The diverging diamond interchange, for example, is growing in popularity. At the Federal Highway Administration (FHWA), it is known as the double crossover diamond interchange and is the subject of a TechBrief available at www.fhwa.dot.gov/publications/research/safety/09054/index.cfm.


More exotic interchanges include the median U-turn intersection (www.fhwa.dot.gov/publications/research/safety/09057/index.cfm); the continuous-flow intersection (i.e., displaced left-turn intersection) TechBrief: www.fhwa.dot.gov/publications/research/safety/09055/index.cfm; and the quadrant roadway intersection (www.fhwa.dot.gov/publications/research/safety/09058/index.cfm).


Alternative, or unconventional, intersection designs offer a traffic engineer the chance to develop a design that is tailor-made for the context of the area in which it is going to function, with different characteristics such as capacity and conflict points between vehicles, pedestrians and bicyclists.


“Several innovative alternative geometric intersection and interchange designs are now available which reduce crossover, or conflict, points or move the conflict points away from a main intersection,” according to the FHWA. “FHWA studies of alternative intersection and interchange designs implemented within the last few years show an immediate and significant reduction in the number of total crashes, injury crashes and fatal crashes (up to 53, 42 and 70 percent respectively).”


Alternative intersection designs also are the subject of detailed study in the second round of the FHWA’s Every Day Counts Initiative introduced last month.


Every Day Counts is an effort focused on shortening the time needed to complete highway projects through the use of new technologies and innovative processes.


Every Day Counts 2 will promote 13 innovations to state, local and regional transportation agencies, as well as to the design and construction industries. These initiatives range from innovative construction management techniques to paving machinery designed to use global positioning systems to achieve higher-quality, longer-lasting roadways.


FHWA launched the EDC initiative in 2010 and has already seen dramatic results from the first round of technologies. FHWA has high hopes for this new set of technologies—including intersection and interchange geometrics—during the next two years.

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