Under the planned reconfiguration, pedestrians and cyclists heading toward Key Biscayne would have to stop and cross three lanes of traffic on Virginia Key at a light in front of the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

“We would have to figure out if there’s any impact, and how bad it is with traffic, and take whatever necessary action to adjust it or close it if necessary — meaning closing the bridge to all pedestrians and cyclists,” Cotarelo said. “It is a possibility.”

Cyclists have already had to adapt to the partial lane shutdown, sharing the protected sidewalk with slow-moving pedestrians or choosing to ride with cars on eastbound auto lanes. Some cyclists have reported crashes on the westbound bike lane, due in part to unfamiliar signage and an inconsistent lane width. Now, cyclists will have to make room on that lane for bikes riding to and from Key Biscayne, and for people on foot.

Miami-Dade does not intend to replace the entire portion under the westbound lanes of the bridge — only the corroded beams, or girders, which were built in 1944 and exposed to saltwater, and the asphalt deck that lies on top of them. The bridge’s foundations appear structurally sound.

The girders will be replaced with the same concrete-encased beams supporting the eastbound lanes of the bridge, which were built in 1983. That portion of the bridge can handle the load of an extra auto traffic lane, Cotarelo said.

The repairs, which would not begin until after the tennis tournament, are expected to cost $25 million. To finance the project, the county plans to issue bonds backed by the Rickenbacker Causeway tolls, which would have to be raised to $1.75 from $1.50 for cars. Some county commissioners balked at that idea at a transportation committee meeting Monday, saying they would not support a toll hike unless the county fast-tracks its plans to use SunPass — instead of C-Pass— tolls at the causeway.

Once repairs begin, the project could last nine months with round-the-clock work, according to the county. But it could take longer if the county insists on having four lanes open throughout the repairs, as his administration is considering, Gimenez said.

As part of the repairs, Miami-Dade will widen the bridge’s westbound lanes by at least 12 feet — allowing the county to create a protected sidewalk, which does not currently exist. During the repairs, that extra space could allow one westbound lane open at all times, if the contractor is able to fix one of the lanes completely before moving on to the second one.

Gimenez said that requirement could extend the repairs by a couple of months.