Traffic concepts such as crisscross overpasses may annoy drivers, but experts say they work

Roe Avenue and Interstate 435 in Overland Park features the Kansas City area’s sixth “diverging diamond interchange.” The road configuration’s crisscross pattern “is like going into a maze,” one driver says.
Roe Avenue and Interstate 435 in Overland Park features the Kansas City area’s sixth “diverging diamond interchange.” The road configuration’s crisscross pattern “is like going into a maze,” one driver says. The Kansas City Star

On Roe Avenue at the revamped interchange above Interstate 435, more than two dozen signs tell drivers where to go and what not to do.

Wrong way. No right turn. Yield here for pedestrian.

The signs and signals cajole motorists into crisscrossing at the overpass, and possibly crisscrossing again. A kind of roadway do-si-do.

Engineers call it a “diverging diamond interchange,” which is among the newer and, at first blush, wackier concepts in street design and traffic control.

Such interchanges are up there with the proliferation of roundabouts, flashing yellow turn arrows, and intersections where traffic lights have vanished, replaced in some cases by two-way stop signs that blink red.

It’s all making once-humdrum commutes a learning experience that can baffle, local motorists say.

The Roe diverging diamond interchange, the sixth in the Kansas City area, “is like going into a maze,” said area resident Steve Katz, who drives shuttles and has transported rental cars for a living.

“I’m not comfortable going in,” he said, “and I’m a seasoned driver.”

If it puts the interchange’s 20,000 daily users on edge, well, good, the experts say. The diverging diamond interchange and some other ideas gaining traction among traffic engineers are partly intended to keep motorists from getting too comfortable and making mistakes.

“They force people to pay attention, and that’s a good thing,” said University of Kansas psychologist Paul Atchley, who has studied motorist behavior.

Atchley acknowledged that being on the lookout isn’t what many motorists want. But there is a funny logic and extensive testing behind most things traffic engineers do, even if they annoy drivers who would rather fiddle with dashboard screens and phones on the arm rest.

Take roundabouts, a near-constant source of driver disdain.

Motorists merging into one must slow down and be on guard for other cars whipping around. That makes driving safer, the thinking goes, and officials say crashes almost always are reduced when conventional intersections are converted into circular ones.

Many other intersections are adopting new twists, too. They include the flashing yellow arrow for left turns.

The flashing yellow arrow means oncoming traffic has a green light. You must yield. Do not speed up.

(In some locales the flashing yellow has replaced the flashing red arrow, thanks to a Michigan study that found drivers confused over whether or not a flashing red meant they could turn.)

Robert Burger is a concerned citizen of what he calls “Lenexa, home of roundabouts and flashing yellow arrows.” He thinks some of the newer mutations to motoring around may prove safer over time.

But in the weeks it can take for drivers to get used to them, “I’m worried somebody’s going to get killed,” he said.

He is of the belief that traffic engineers are gunning for prizes and peer recognition by getting all fancy.

Carol Estes chuckled.

As a traffic committee coordinator for the American Public Works Association, based in Kansas City, Estes said she hears similar gripes and unsolicited advice from people at social events.

“You get cornered,” she said. “It seems everyone with a driver’s license qualifies as a traffic engineer.”

Flash happy

Among many readers of The Star who bring riddles of the road to the newspaper’s attention, typically via “The Watchdog” column, Burger’s example of the intersection of Quivira Road and 79th Street is a dandy.

Here’s how the four-bulb traffic signals there instruct you to turn left in rush hour:

Bottom bulb shows a solid green arrow for about 10 seconds. That changes to a yellow arrow that stays put — second bulb from the top — for three seconds.

Then red arrow, top bulb, for not quite two seconds.

Then flashing yellow arrow, third bulb down, for 30 seconds or more. Then another quick look at the solid yellow arrow above it before the light goes red.

Lenexa transportation manager Steve Schooley said the colorful sequence is intended to put lines of left-turning drivers on alert that the signals for oncoming traffic are changing to green. The rules are going “from protected to permissive,” as engineers say.

So don’t just keep turning. “Yield on flashing yellow,” say some helpful signs.

Schooley said a 2012 study, done a year after the city installed its first flashing-yellow turn lights, showed no change in the rate of accidents at those corners. He took it as a good indicator that drivers had adjusted to the change.

In downtown Kansas City and across the area, lots of intersections once adorned with traffic lights are switching to crossings with two-way stop signs.

That saves the public money for signal maintenance, shortens drive times and “potentially reduces greenhouse gases emitted from cars waiting for a traffic light to change,” said Sean Demory, Kansas City’s spokesman for public works.

“There’s a learning process any time you make changes,” he said. “But we see that drivers get used to the changes in rather quick fashion.”

Even roundabouts can be your friends.

Packed into an Overland Park neighborhood near 75th Street and Metcalf Avenue are nine — nine! — mini-roundabouts. They’re designed to frustrate intruders who speed through to avoid sitting at stoplights on the main drags, said Brian Shields, the city’s traffic engineer.

A roundabout built some years back in Kansas City, North, featured tall native grasses planted around the perimeter. Looked swell, but area resident Harry Sievers brought to the city’s attention a problem: The grass obscured the view of drivers trying to merge with circling cars.

So the city replaced the tall grasses with concrete. And that helped make the roundabout at 72nd Street and Waukomis Drive safer than the plain-vanilla intersection that existed before.

According to the Insurance Institute for Highway Safety, changing intersections with signals or stop signs to roundabouts reduced injury crashes by an average of 80 percent.

“Roundabouts work,” said Sievers, a TWA retiree who admired their efficiency in visits to Europe. “Once you get used to them, there’s no problem.”

He thinks, though, that the merging know-how of young drivers could be enhanced: “To get a driver’s license you should know how to enter a roundabout.”

And there’s plenty to learn.

The Kansas Guide to Roundabouts, second edition, weighed in at 500 pages when state officials released the two-volume set last year. Some of its instructions seemed a bit hazy, such as:

“For a three-lane roundabout, note how the center lane is assigned on the lane-use signs. It might be limited to going straight, or it might be used for a left or right turn.”

The Kansas Department of Transportation has built roughly 100 roundabouts since the first one landed in Manhattan in 1997. The Missouri Transportation Department has built 28 just in the Kansas City region covering nine counties.

Those roundabouts don’t include the many conceived by cities, neighborhoods and developers — of which nobody can keep score.

When the counterclockwise intersections began appearing across Kansas, “people thought we were running some weird experiment,” said KDOT design engineer Scott King. “Now we’ve got communities asking for them” in hopes of eliminating wrecks caused by motorists running through stop signs.

Interested? Go to RoundaboutsUSA.com.


The diverging diamond interchange also has an “official website,” www.divergingdiamond.com, launched by roadway guru Gilbert Chlewicki.

The Maryland man claims to have first sketched out the concept in a 2000 term paper he wrote as a first-semester graduate student. He also coined the moniker “diverging diamond,” he said, after giving some thought to calling the design what it really is, a “crisscross” interchange.

“My professor thought crisscross sounded too much like the 1980s pop star Christopher Cross,” said Chlewicki, who heads the transportation design firm ATS/American.

He attended the 2009 opening of the nation’s first diverging diamond interchange — the junction of Missouri Route 13 and I-44 in Springfield. Dozens would follow.

By allowing drivers to turn left onto interstate ramps, without waiting for oncoming cars to clear, officials charted smoother traffic flow and fewer collisions.

Slow-rolling trucks no longer clogged things up for everyone else.

But as motorists on Roe can now attest, it just feels wrong.

Northbound, you switch to the left-hand lanes; southbound, do the same. Then for those of you not turning left to get on I-435, crisscross back.

With several diverging diamond interchanges now sprinkled around and at least three on drawing boards, the Kansas City area has emerged as a leader in America’s movement toward such interchanges, Chlewicki said. He noted that crisscrossing an existing overpass can slice more than 70 percent off the cost of adding lanes and building new ramps.

Near Grandview, famous for its crazy interstate mixmaster, motorists are getting used to weaving through the diverging diamond interchange at Botts Road and Missouri 150. They include Grandview police Sgt. Dean VanWinkle, who has but one worry about the design.

Intoxicated drivers. “Surely,” he said, “some drunk factor should plug into the equation.”

To reach Rick Montgomery, call 816-234-4410 or send email to rmontgomery@kcstar.com.