Diamonds are a traffic hound’s best friend

The problem

Kansas City resident Trent Platz has driven on the nation’s first diverging diamond interchange in Springfield and has seen how much it improved traffic there.

He wonders why the state can’t do the same at Missouri 152 and Interstate 35 in Liberty.

The answer

Since Kansas City got its first diverging diamond interchange at Interstate 35 and Front Street, they have been popping up all around the area. These interchanges, pioneered in Europe, move traffic briefly to the left side of the road, which allows drivers to make left turns without having to worry about opposing traffic.

The Missouri Department of Transportation has analyzed the Liberty interchange and concluded that diverging diamonds (DDIs) aren’t the best solution to every traffic problem.

“In a nutshell, a DDI would work, but improving the existing diamond works better,” said senior highway designer Joshua Scott.

The two layouts function comparably for current traffic counts, but when expected traffic growth is figured in, the traditional diamond pulls ahead. Some of the reasons:

Diverging diamonds make the most difference for turning traffic. Here, there’s a great deal of “through” traffic, and a DDI can allow only one direction to move at a time.

It’s difficult to coordinate traffic signals along Missouri 152 with a DDI.

There’s little, if any, cost savings. With a diverging diamond, the bridge over I-35 wouldn’t have to be as big, but more pavement would have to be rebuilt nearby.

If traffic increases more than expected, the DDI will become too congested to function adequately.

The Watchdog says that when the pollen is flying, the Handsome Hound becomes too congested to function adequately.

This story was originally published May 27, 2014 at 6:17 PM with the headline "Diamonds are a traffic hound’s best friend."