Heavy traffic on Interstate 75 moves slowly Sept. 8 in Forest Park, south of Atlanta. A massive evacuation has clogged highways as residents of Florida drive north to flee the state. (Mike Stewart/AP)

Florida’s primary highways going north were filled with heavy traffic Friday as thousands of residents fled the areas of the state under hurricane warning.

On some parts of Interstate 75, near the Georgia state line, highway officials have opened up the shoulder lanes to drivers. In Georgia, southbound lanes of the 75 Express Lanes were reversed to increase the road capacity for the evacuees.

“Traffic is heavy but flowing,” said Florida Highway Patrol spokesman Steve Gaskins.

With the window to escape the path of Irma in Florida rapidly closing, thousands of residents were on the road in what could be one of the largest mass evacuations in the country’s history. Interstate 95 along the east coast and Interstate 75 near the west coast face significant gridlock.

By noon Friday, traffic in South Florida was moving smoothly north on Florida’s Turnpike with some delays, a state highway spokesman said.  Vehicles were also moving smoothly on I-95 and I-75 as drivers left the region.

The flow of I-75 through central and northern Florida was slower, which prompted the decision to open the shoulder lanes.

Georgia highway officials said the I-75 South Metro Express Lanes will remain northbound until further notice to handle heavier traffic as evacuees travel inland from coastal Georgia and Florida. Tolls are also being waived starting Friday, and lanes will be open to all vehicles whether they carry the state’s toll pass or not.

Several crashes caused delays Friday. But highway patrols were clearing up wrecks and stranded cars off the roadways as quickly as possible.

“We will continue to assist stranded motorists and clear crashes (as soon as possible) so there is no interruptions in the flow of traffic,” said Lt. Yosdany Veloz, a spokesman with Florida Highway Patrol in South Florida.

State highway police continued to escort tanker trucks delivering fuel. At a news conference, Florida Gov. Rick Scott (R) said the delivery of fuel was critical to get residents to evacuate, and he urged gas stations to stay open as long as possible.

He asked residents planning to evacuate to not delay their departure any longer. About 1700 troopers are on the roads to help families evacuate safely, he said.

“Why wait until the winds start. If you know you are going to evacuate do it today,” he said. “Get on the road and get out of here.”

Forecasters said Irma will be near South Florida by Sunday morning and could potentially make landfall somewhere in the state. The Capital Weather Gang said, “It’s still uncertain whether the southwest or southeast coast will catch the storm’s most destructive brunt, or somewhere in between.”

Meanwhile, Fort Lauderdale International Airport said it would be closed Saturday and Sunday. The airport’s garages are full, officials said, urging travelers with flights out Friday to find another location to park their vehicles.