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New Houghton Road interchange at I-10 first of its kind in S. Arizona
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New Houghton Road interchange at I-10 first of its kind in S. Arizona

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The new Houghton Road overpass at Interstate 10 uses a “diverging diamond” interchange to move a higher volume of traffic.

All lanes on the Houghton Road overpass at Interstate 10 are now open, making it Southern Arizona’s first “diverging diamond” interchange.

The Arizona Department of Transportation said this week the rebuilding of the interchange has been completed. Traffic lanes had been opened at the interchange earlier this year as final work was completed.

The $24 million project features a diverging diamond interchange, which is designed to improve safety and traffic flow in a rapidly growing part of southeast Tucson, ADOT said.

Unlike a traditional diamond interchange, each direction of Houghton traffic temporarily shifts to the left while crossing the freeway. This allows for left turns onto the entrance ramps without waiting at an additional traffic signal.

The design also promotes safety because drivers turning left don’t cross traffic while entering the on-ramp. Signals, signs and pavement markings help guide drivers through the interchange, ADOT said in a news release.

The interchange features larger entrance and exit ramps, along with more space for traffic to merge onto I-10 westbound.

Over the freeway, the old two-lane Houghton Road bridge was replaced with a structure that features six lanes and improved access for pedestrians and bicyclists.

ADOT said traffic engineers chose the diverging diamond design because it can handle higher traffic volumes in the growing part of Tucson, where traffic is expected to increase by as much as 50% by 2045.

While all lanes are open, intermittent lane restrictions are possible in the next two weeks as construction crews wrap up minor project details. In the spring, drivers should expect overnight lane restrictions when warmer overnight temperatures allow for final paving on I-10 and the ramps.

More than 115 diverging diamond interchanges are in use in the U.S., including two half-diverging diamond interchanges on the Loop 202 South Mountain Freeway and a full diverging diamond interchange I-17 and Happy Valley Road in Phoenix.

More information about the I-10/Houghton Road project is available at azdot.gov/i10Houghton.

Video courtesy of the Arizona Department of Transportation.


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