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City officials see different interchange on Horizon

Henderson officials have a problem: Too many people are using Horizon Drive to get on the freeway at the same time.

Traffic backs up, especially during morning rush hour. It’s quite a mess. Sometimes traffic even backs up on the freeway exits.

It got that way because the area, near the southern edge of the city along U.S. Highway 95, has many thousands of people living there and not much access to the freeway.

There’s College Drive, which is a ways south, and there’s the Las Vegas Beltway to the north.

There’s development in both directions. And everyone wants to get on the freeway.

City officials looked at solutions. Maybe they could add another turn lane. It’s cheap but doesn’t do much to fix the problem.

They thought about making the bridge over the freeway bigger, which would allow more traffic to flow at the same time without bottling things up.

Except that would cost more than $20 million.

No one has $20 million.

So they’re going to try something that’s never been done in Southern Nevada. They’re going to make you drive on the wrong side of the road.

“I know it looks complicated on paper, but when you actually drive it, it’s just the easiest thing in the world,” said Scott Jarvis, a project engineer with the city.

Later this year, the bridge over the freeway will be reworked into what’s called a diverging diamond interchange.

The goal is to eliminate left turns. Traffic engineers hate left turns. They’re one of the leading causes of car crashes. And they make drivers wait.

That’s why UPS, the delivery service, famously has designed routes for its drivers that avoid most left turns.

The diverging diamond basically works like this: Drivers shift from the right side of the road to the left side of the road at the start of the bridge over the freeway. If they want to get on the freeway, it’s no problem; just keep going. If they want to go straight, oncoming traffic is waiting at a red light.

Meanwhile, traffic going the other direction does the same thing. There are no left turn lights.

Once drivers reach the other side of the bridge, they’ve been rerouted back onto the proper side of the road.

It sounds confusing. It even looks confusing on a diagram or a map.

But Jarvis and other transportation experts say there are plenty of signs, road striping and concrete barriers to make driving through one a humdrum experience.

Diverging diamond interchanges began popping up in this country a few years ago, though there have been a couple in France for decades.

The first such interchange in the United States was built in Missouri in 2009. Officials there say crashes were cut in half almost immediately. The inter­change cut wait times, too.

They are the brainchild of Gilbert Chlewicki, a transportation expert. He introduced the idea to a group of transportation experts, and it took off.

“You eliminate the conflicts you get with left turns,” said Dwayne Wilkinson, a senior project manager with the Nevada Department of Transportation.

The first such interchange in Nevada was opened in Reno last year. So far, not a single driver has driven the wrong way through it, he said.

Jarvis, with the city, said the project’s design is almost complete. Construction should start by year’s end and should take about six months to finish.

The total cost will be about $2.6 million, a tenth of the cost of rebuilding and enlarging the entire structure.

Henderson will contribute $131,579, and the rest is federal highway money funneled through the state.

What that will pay for is new striping and curbing, new signs, new medians, a new bike path and some traffic signals, which will probably have to be rewired.

There will be no need to tear down the old bridge, or to acquire new land or cause any major disruptions in the area.

Contact reporter Richard Lake at rlake@reviewjournal.com or 702-383-0307.

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