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Is the roundabout too small? KDOT says no

Staff reporter

County residents are closely monitoring the construction of a roundabout at the U.S.-50/77 intersection at Florence.

Speculators insist it appears to be too short to accommodate semi truck/tractor traffic despite extensive design work by Kansas Department of Transportation.

Just how big is the Florence roundabout?

According to Joe Palic of the Marion KDOT field office, the interior is 150 feet and exterior is 210 feet.

A concrete apron serves as a buffer to allow trucks to better track.

"The apron at the Florence roundabout is three inches high," he said, which is an improvement over other roundabouts. The apron at Newton's roundabout has a height of eight inches.

There are 40 roundabouts in the state of Kansas but only eight are on state highways. The Florence roundabout will be the third rural roundabout designed and implemented in the state and the second to have a five-legged intersection.

"It is very similar to the roundabout near Paola," said KDOT senior traffic engineer Cheryl Lambrecht.

The design of roundabouts is based on the type of traffic that uses it. An apron is constructed to give truck drivers room for error and to accommodate larger trailers.

The average length of a semi tractor-trailer is 73 feet from front axle to rear axle.

"Double trailers have an extra hinge between trailers," said Lambrecht, "and actually take less width than a regular semi truck. They're more flexible."

Truck drivers who have problems are those driving 60-foot long trailers without a hinge.

In comparison, the roundabout at Newton is round. The roundabout being constructed at Florence is an oval, said Lambrecht.

KDOT district four engineer Mike Stringer said there's a reason roundabouts aren't constructed larger.

"If it was built large enough to accommodate larger trucks, then smaller vehicles would be able to drive faster through it," he said, which eliminates the purpose of the roundabout — to slow down traffic.

"I have yet to see a vehicle too large to get through the roundabout," said Stringer about the Paola intersection. "I've even seen a house being hauled maneuver through it."

A roundabout was constructed near Paola in 2001 for similar reasons as the one at Florence. Previously, there was a two-way stop control.

In 3 1/2 years, there were 17 right-angle crashes that resulted in 25 injuries. Since the roundabout has been installed, there have been eight crashes caused by failure to yield and rear-end collisions but there were no injuries.

At Florence, there had been numerous fatality collisions at the dangerous intersection primarily caused by failure to yield at the stop sign.

"I've heard comments from travelers that motorists really do slow down and yield," Lambrecht said.

Truck drivers like roundabouts better than stop signs because they are able to maintain forward momentum.

"Instead of going from 65 to 0 mph, they go from 65 to 15 to 25 mph," she said.

Regardless of what drivers think, roundabouts are designed to slow down traffic and minimize injuries if a collision should occur.

Completion of the roundabout and the opening of U.S.-77 are slated for Sept. 29.

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