Updated 

Henderson to get valley’s first diverging diamond interchange


At the Horizon Drive overpass above U.S. Highway 95, X marks the spot for a hidden treasure.

By early fall, motorists will find a big diamond there.

But the treasure motorists will find is even more valuable — their saved time.

Too cryptic and confusing? Warrior reader Joan also is looking for answers.

“Last year, we read that the interchange at Horizon Ridge Parkway and Horizon Drive was going to be improved with some sort of an X pattern. They said it was going to start the beginning of this year. What happened to that project?”

Well, Joan, the project you’re inquiring about took a little longer than expected to get started, but it’s on its way. The Henderson City Council recently approved transforming the Horizon Drive interchange at U.S. 95 into Southern Nevada’s first diverging diamond interchange.

Yeah, “diverging diamond interchange” is a mouthful, but trust me, if you’re one of the estimated 27,500 motorists who use that road on an average day, you’re going to like it.

Simply, a diverging diamond interchange uses traffic signals, physical barriers and pavement markings to temporarily shift traffic to the left side of a street. What that does is help keep traffic flowing because it creates two pairs of unimpeded left turns onto and off the freeway.

Henderson has some major traffic problems on Horizon Ridge Parkway, which runs parallel to the highway and is a popular route for residents of several neighborhoods to access northbound U.S. 95 toward Las Vegas.

Motorists traveling south on Horizon Ridge would encounter a traffic signal and a left turn crossing traffic at Horizon Drive. Then, they would come to another traffic signal at the southbound freeway exit. And then another at the northbound freeway entrance, at which motorists would have to make a left turn against crossing traffic.

All those traffic signals are within about 200 feet of each other. The end result was a line of traffic backing onto Horizon Ridge in the mornings.

In the evening, the backup occurs on the Horizon Drive exit off southbound U.S. 95, but most of those backed up are angling to go east on Horizon Drive.

Diverging diamonds can handle 650 left turns an hour, about twice the number of a conventional interchange.

Scott Jarvis, a project engineer for the city of Henderson, got the idea for installing a diverging diamond interchange to solve the problem from the C A Group, a Las Vegas-based engineering consultant.

It turns out the diverging diamond is the next big thing in traffic design. It even has its own website, divergingdiamond.com.

There are 34 such interchanges in the United States, with the closest one to Las Vegas on St. George Boulevard and Interstate 15 in St. George, Utah.

Missouri is the king of diamonds with 13 of them, Utah has five and there’s even one in Reno at Moana Lane over Interstate 580.

“It’s the newest tool in the toolbox,” said Jarvis, who said work would begin in early summer and be completed by fall.

Crews will work at night so there will be minimal traffic disruptions, and one lane of traffic will be open in each direction at all times during construction.

Toward the end of the project, Jarvis said the intersection would have to be closed for final striping.

The redesign will cost $2.3 million, and federal highway money is being used for the project, which will include clearing existing medians, flaring the left-turn entrances and exits, replacing and relocating the existing traffic signals, building new medians and striping the new lanes. Because the redesign fits within the existing bridge span, there’s no need to widen the bridge.

Jarvis has driven the Reno diamond.

“I think what amazed me the most is that you just follow the flow of traffic and by the time you realize that, ‘Whoa, I’m on the other side of the road,’ you’re guided back to the right side again,” he said. “People won’t even realize they’re in it.”

Jarvis, who doubles as Henderson’s bicycle program manager, said the diverging diamond has a hidden bonus — it will make the roads safer for bicyclists.

Horizon Drive is an important east-west link for Henderson and the first place for pedestrians and bicyclists to cross U.S. 95 south of Auto Show Drive.

GASOLINE FORECAST

The U.S. Energy Information Administration has a nice summer surprise for motorists.

The average gasoline price is forecast to be 1 to 2 cents less than it was in summer 2013.

The agency said the national average is expected to peak at $3.66 a gallon in May and steadily decline to $3.46 by September. That’s a penny less than a year ago.

Questions and comments should be sent to roadwarrior@reviewjournal.com. Please include your phone number. Follow @RJroadwarrior on Twitter.