Town engineer finds roundabout flaws

A traffic engineer hired by the town to dispute the city of Sarasota’s roundabout plans for U.S. 41 believes the city’s engineer used incorrect data that allows the city to show traffic moving more efficiently through the roundabouts than what’s actually possible.

At the Town Commission’s Thursday, Nov. 19 regular workshop, Juan Calderon, a professional traffic-operational engineer with Miami-based FTE, showed a model with cars running into one another in the proposed roundabouts. The engineer says cars driving into the roundabout at a gap of 1.7 to 2 seconds is extremely unrealistic.

“The gap between one car and another is extremely aggressive,” said Calderon, who explained he has designed roundabouts in Miami that have motorists riding up on each other with car gaps of approximately 3 seconds. Calderon suggests a gap of at least 3.5 to 4 seconds.

Calderon also said the growth rates the city’s engineer applied to the project are inaccurate and said the roundabouts would divert traffic backups elsewhere, onto busy thoroughfares such as U.S. 301 and Fruitville Road.

Calderon reiterated to the commission that he is not against roundabouts.

“I have built many roundabouts in Miami that work well,” Calderon said. “But there are some scenarios listed for these particular roundabouts that raise questions and need to be reviewed.”

Calderon also said the roundabouts planned for U.S. 41 do not have enough right of way necessary to contain all the roundabouts as proposed.

And, a roundabout proposed at U.S. 41 and Gulfstream Avenue, Calderon said, will do nothing to improve the traffic flow that already exists in that intersection.

Vice Mayor Robert Siekmann asked Calderon if the city’s roundabout proposal would help increase pedestrian traffic to the bayfront, which was the city’s initial primary goal for building the roundabouts.

Said Calderon: “Roundabouts allow for continual movable traffic. Pedestrians have to wait for breaks in traffic to get across.”

Rod Warner, chairman of The City Alliance, a Sarasota collation of city residents and business owners in favor of roundabouts, defended the plan.

“The Florida Department of Transportation will decide whether this plan will work or not,” Warner said.
In the middle of his speech, Siekmann cut Warner off.

“OK, we’re done here,” said Siekmann, who quickly asked town staff to deliver a copy of the engineer’s findings to local planning organizations and the Florida Department of Transportation. “This information is of value and should be shared.”

The town’s engineer will also continue to analyze any information the city submits to the state for its roundabout project.

Said Commissioner Jim Brown: “We should continue to monitor how the city reacts to the shortcomings our engineer has revealed.”

Contact Kurt Schultheis at [email protected]


TWO BETTER THAN ONE?
The one test roundabout that two city commissioners have suggested at U.S. 41 and 10th Street may not be singular much longer.

Sarasota City Commissioner Terry Turner said the information he’s received about roundabouts is that they work best in pairs or as part of a network of roundabouts.

Turner suggested building a roundabout at 14th Street to couple with the one the city is planning at 10th Street. The majority of the commission has agreed to build two at once.

The idea for a test roundabout was to get drivers used to driving in a roundabout and to demonstrate that the proposed connectivity plan would work.

The 10th Street roundabout is estimated to cost $2.9 million. There is no estimate yet for a roundabout at 14th Street.
— Robin Roy