The 14-hour traffic jams and gasoline shortages that accompanied last year's killer hurricanes led to improved evacuation plans for some hurricane-prone states. But that does not mean the next evacuation will go smoothly.

On the eve of hurricane season, emergency experts are worried that many large metropolitan areas simply cannot clear out quickly without problems, even those cites that are used to evacuating for storms.

"I'm happy to see they're pulling out all the stops this time," said Brian Wolshon, a Louisiana State University engineer.

But he asks: "Is it possible to smoothly evacuate? I don't see it. It just overwhelms what we can realistically expect to provide."

Communities in Texas and Louisiana have rewritten their evacuation plans to add fleets of buses, improve traffic management and ensure a large supply of gas.

Still, when the winds begin to howl, Wolshon and other experts worry that any plans — no matter how specific — will not be enough.

Hurricane Katrina killed more than 1,500 people, many of whom could not leave because they did not have cars, or who did not want to endure snarled traffic. A few weeks later, 3 million people fled Hurricane Rita when it appeared the storm would slam into Galveston and swamp Houston.

The storm turned east, sparing the most populated areas, but 137 people died in the evacuation, many succumbing to heat exhaustion along traffic-choked and gas-deprived highways.

Evacuation nightmares are nothing new in Florida, where 1.3 million people were told to leave the state's Atlantic coast when Hurricane Floyd threatened in 1999, backing up traffic 30 miles or more.

The problem has worsened in recent years as coastal populations have grown.

Florida authorities now plan to advise residents who live in areas vulnerable to storm surges to go to higher ground within their counties, to a friend or relative's home, or to a shelter. Those who are not in storm surge zones or mobile homes should just hunker down, as most newer homes can withstand hurricane-force winds.

Emergency managers also stress that each family needs a plan for evacuations. Larry Gispert, emergency management director for Hillsborough County, marveled that a study of people who hit the road before Floyd indicated that most did not know where they were going.

"How dumb is that?" he said.

The new evacuation plans in Louisiana and Texas acknowledge that millions will flee when only thousands are in danger. So planners have to expect more traffic and encourage many scared residents to stay home.

After Floyd, officials in Florida developed "contraflow" plans for six major highways in which traffic runs in one direction to accommodate a mass evacuation.

Texas has adopted a similar practice and now plans to open contraflow lanes 45 hours before tropical storm-force winds hit the coast. Last year, Houston waited several days before turning the highway lanes around, bearing much of the blame for clogged roads.

Texas authorities had forecast about 700,000 evacuees in a hurricane. During Rita, nearly three times that number packed up and fled.

"It's a simple equation: if you have too much demand, you're going to overwhelm your capacity," Wolshon said. "There's a limit, and we're stretching it about as far as we can go using contraflow."

During a hurricane drill in Texas last month, emergency officials planned for everyone to leave and for some families to evacuate in two or more cars.

"We did behavioral studies and found that people are not going to leave $30,000 cars behind," said Jack Colley, chief of the governor's Division of Emergency Management.

To improve evacuations, Texas focused on fuel shortages and evacuating the elderly and those without cars. Plans are now in place to put external, rubber fuel bladders at gas stations to double fuel capacity. Officials say they have also lined up trains, each capable of transporting 1,600 people.

New Orleans is adopting a similar reliance on trains and buses. In Georgia, many coastal counties are also doubling up on the number of buses on standby.

Natalie O'Neill, mayor of the coastal Texas suburb Taylor Lake Village, spent 18 hours driving 150 miles from Houston to Austin during the Rita evacuation. In a hurricane, the 4,000 residents in her town are the first to leave.

Whatever happens, she just wants it to be quicker next time.

"It can't possibly be any worse," O'Neill said. "As long as I'm not sitting in traffic again all day, it will be better."