More than half a million people fled the S.C. coast as Hurricane Floyd approached in 1999. Next time, it could be more than twice that.

Traffic jams are certain. But officials hope to ease the misery that accompanied Floyd by reversing eastbound interstate lanes and encouraging coastal residents and visitors to hit the road earlier when a storm approaches.

"You will never be able to make an easy commute ... with a couple hundred thousand folks leaving the same time as you do," S.C. Gov. Mark Sanford said Tuesday in Charleston, as the first hurricane of the season stormed ashore in Texas.

New plans outlined by Sanford and other officials, however, could shave a few hours off the total evacuation time, and keep a mass exodus from becoming the 18-hour traffic jam many people sat through as Floyd approached.

Among the latest plans:

• U.S. 501 out of Myrtle Beach was added to the list of roads officials could reverse in an evacuation. Four lanes would flow away from the coast starting just west of Conway and lasting through Marion. U.S. 501 would remain two-way closer to the beach, officials said, because traffic needs to move in both directions.

• To speed up an evacuation of Hilton Head and points south of Charleston, both eastbound lanes of U.S. 278 could be reversed to Interstate 95, if needed, with U.S. 21 also flowing away from the coast. Earlier plans had called for only partial reversals.

• All lanes of Interstate 26 would lead away from Charleston, but more exits would remain open under the revised plans unveiled Tuesday. The old plan, created soon after Floyd, forced everyone in the reversed lanes to drive all the way to Columbia.

N.C. officials have similar plans for Interstate 40 from Wilmington toward Raleigh, which they would reverse in an evacuation.

"Hopefully we'll never have to use it," said N.C. Highway Patrol Sgt. Everett Clendenin. "But statistically, we will."

About 530,000 people fled the S.C. coast as Floyd approached, according to a study conducted for federal emergency planners. They were among 3.5 million evacuees from Florida to Virginia.

The next evacuation could require moving 1.3 million people from the S.C. coast in more than 600,000 vehicles, officials said at an emergency management conference in March.

Since Floyd, South Carolina has added traffic cameras and speed detectors to help them make decisions about which lanes to reverse.

Many evacuees complained that officials waited too long and didn't have effective plans in 1999.

Even reversing lanes won't make the next evacuation speedy. But officials hope to keep traffic moving and avoid snarls that trap people in the same spot for hours.

Computer models offer some hope. Traffic should move at about 40 mph on I-26 with the lanes reversed, said S.C. Highway Patrol Lt. Col. Harry Stubblefield.

But evacuating the coast still is expected to take up to 24 hours. The lane reversals could shave six or seven hours off that in Myrtle Beach, Stubblefield said, and four hours from Hilton Head.

"The earlier people leave, the quicker the evacuation will be," he said. "They still can't wait until the last minute."

The plans remain to be tested under real-life conditions, but this year could provide the chance. The National Hurricane Center predicts a "very active season," with as many as 15 named storms and up to four major hurricanes with winds of 111 mph or more.

The long-term average is about 10 named storms a year and two major hurricanes. Favorable winds and warmer ocean waters are among the factors pointing to a stronger season this year.

On average, two or three hurricanes hit the United States in similar seasons, the national Climate Prediction Center says.

Most hurricanes that threaten the Carolinas form in August or September.

The Carolinas haven't had a direct hit from a hurricane since Floyd flooded much of eastern North Carolina three years ago. In South Carolina, a hurricane hasn't come ashore since Hugo, which left a path of destruction from Charleston to Charlotte in 1989.

The Atlantic hurricane season started June 1 and lasts through Nov. 30. -- THE ASSOCIATED PRESS CONTRIBUTED TO THIS REPORT.

-- SCOTT DODD: (704) 358-5168; SDODD@CHARLOTTEOBSERVER.COM.