Miami-Dade County will make small road improvements beginning Monday night to ease traffic flow on the bridge between Virginia Key and Key Biscayne, which has been partially closed due to structural problems.

The road work includes paving over parts of the median on both sides of the Bear Cut Bridge to make it easier for vehicles to get on and off the structure. The work will only take place at night, between 8 p.m. and 5 a.m., and should be completed by Friday, subject to weather or other unexpected circumstances, Miami-Dade’s public works department said in a news release Saturday.

Major work to repair the corroded steel beams that support the bridge’s two westbound lanes is not expected to begin until after the Sony Open tennis tournament in March, according to the department. The estimate is based on how long it will take the county to select a contractor for the project and complete pre-construction work.

Once construction is under way, the repairs are expected to take nine months, Mayor Carlos Gimenez wrote in a memo Thursday to Commissioner Xavier Suarez, whose district includes Key Biscayne.

“Work is anticipated to be performed on a 24 hours per day, 7 days per week schedule,” Gimenez wrote.

At a transportation committee meeting Monday, a group of county commissioners will take an initial vote to waive Miami-Dade’s competitive bidding process to hire a contractor on an emergency basis to repair the Bear Cut Bridge and the smaller West Bridge, which is located immediately after the Rickenbacker Causeway toll plaza and was also built in 1944. The repairs are expected to cost about $25 million, financed by bonds backed by the tolls.

To shore up the reserves for the bond issue, commissioners will also consider hiking the causeway toll prices beginning April 1. The tolls, which were last increased in 2007, would increase to $1.75 from $1.50 for cars. Truck prices would go up as well.

After inspecting the bridge last year, the Florida Department of Transportation recommended imposing weight restrictions on heavy vehicles crossing the structure’s westbound lanes, held up by the beams, or girders, built in 1944 and exposed to saltwater. The other half of the bridge, built in 1983 using concrete-encased beams, is structurally sound.

But the most restrictive weight limits proved unworkable when they went into effect in late December, after the county’s own inspectors had agreed with the state’s assessment. On Jan. 3, Miami-Dade shut down the westbound lanes altogether, allowing all vehicles to travel on the two eastbound lanes — one turned into an outbound lane heading toward the mainland, the other heading toward Key Biscayne.

On Wednesday, the county reopened one of the westbound lanes to cars and motorcycles only. Trucks must continue to use the outbound lane on the southern portion of the bridge.

The changes have also inconvenienced cyclists, who have been asked to ride eastbound on a walled-off pathway with pedestrians and joggers, and westbound on the auto traffic lane that remains closed. Cyclists have reported several accidents since the lane closures, some of them apparently related to the new road conditions.