Longboat consultant finds flaws in Sarasota roundabout data

A traffic consultant hired last fall by Longboat Key to peer review plans for a roundabout at Gulfstream Avenue and U.S. 41 in Sarasota  questioned some of the data used to consider the project, set to begin construction in 2020.

After delivering the bulk of the data review,  consultant CDM Smith Traffic Engineering Services Division recommended the town study the intersection as it operates today, for level of service and delay, and find and study a similar roundabout with a similar traffic volume to see if it performs as expected. In the past year, FDOT added a turn lane from eastbound Gulfstream to northbound U.S. 41, bringing the number to three, to help alleviate traffic backups. 

In September, the commission voted 6-1 to spend $22,760 from its contingency fund to hire CDM Smith to examine information developed in 2018 to inform decisions on construction. In the past, Longboat leaders have been critical of Sarasota's downtown road plans, such as the roundabout, over fears they could lead to snarled traffic all the way to the southern end of the Key. Two years ago, then-Town Manager Dave Bullock said he was skeptical of a roundabout's efficacy at Gulfstream and U.S. 41 in place of more turn lanes in a more conventional intersection design. 

But even at the time of their vote in September, commissioners conceded there was little they could do to deflect the project. Jim Brown was the only vote against the study in September.

“We were hoping CDM would come up with a significant flaw,” Commissioner Jack Daly said at a recent commission workshop. “Instead, they came up with a bunch of minor flaws.”

Arthuro Perez, CDM Smith’s senior project manager, told commissioners the proposed roundabout – already in the design phase – would be no better than the three-turn lane “no-build” alternative of the intersection as it stands. The Florida Department of Transportation, however, has said its traffic projections by 2040 show the roundabout will improve the flow of traffic by 72% over the existing junction during peak morning traffic and 14% more during afternoon traffic.

Among the other issues CDM raised: 

• Design projections between 2020 and 2040 assumed a .56% increase in annual traffic, which CDM described as low. Higher rates of growth, CDM said, would affect traffic through the circle to a greater degree. "Re-evaluation of the historical growth would likely indicate a higher growth rate,'' the report said. 
• Analysis did not account for closely spaced, signal-equipped intersections north and south of the circle, which could affect performance of the circle. A systems approach should have been considered, the report said.
• In 2040, the afternoon peak hour traffic into the circle is projected to back up more on the northbound and eastbound approaches as compared to the southbound approach, a Level of Service the report graded as an "F," while the southbound Level of Service was graded an "A." According to the study: "This is typical of a roundabout where one or two approaches experience no delay while the delays on other approaches are significant. Under a signal control, the signal timing's adjustments will allow for spreading delays to all approaches, without penalizing a specific approach.''

Longboat Key Public Works Director Isaac Brownman met recently with FDOT and said the state is not ready to rethink the project.

“They believe it will enhance the multimodal network and believe it is the right thing to do,” he said.

Sarasota City Engineer Alex DavisShaw said city officials continue to stand behind the roundabout plans. She also highlighted the potential improvements for modes of transportation other than driving, stating the city wanted to improve the pedestrian connectivity between downtown and the bayfront.

“One of the important things the city was looking about with the roundabout at Gulfstream is that it could handle the traffic volume as good as or better than the signal, but also, it’s better for pedestrians,” DavisShaw said. “We wanted it to be more multimodal and create a better sense of place for the corridor.”

FDOT plans to begin construction of the roundabout in 2020, when seasonal traffic peaks have passed. Brownman said the project is expected to take two years to complete and FDOT officials have said all lanes will remain open during construction. 

FDOT will examine traffic counts through the intersection in March and report those back to the town.

“The bottom line is that they are not changing their plan,” Brown said.