Want to beat Memorial weekend traffic? Leave yesterday

John Bacon | USA TODAY

Drivers, start your engines.

The 99th running of the iconic Indianapolis 500 roars to start Sunday, but the nation's highways were already filling up Thursday for Memorial Day weekend.

AAA starts counting travelers for the summer's first holiday weekend on Thursday, and they expect 37.2 million people to attempt the great escape -- travel 50 miles or more from home -- this weekend. That's the biggest Memorial Day weekend mini-migration in a decade. About 33 million of them will drive.

"Following a harsh winter, many Americans are trading in their snow boots for flip flops and making plans to start the season with a vacation getaway," said AAA president Marshall Doney.

Vacationers expecting to beat the rush by leaving Thursday may not find highway solace, at least in metro Washington, D.C.

"Traffic on Washington area highways... is expected to reach its worst point on Thursday afternoon, running counter to a common perception that the Friday before the holiday weekend is the worst time to travel," the region's Transportation Planning Board warned.

In fact, local traffic the Thursday of Memorial Day weekend was actually worse than Friday in each of five years that were studied, the board said. The problem, it seems, is that the pre-holiday Thursday presents the worst of both worlds. Everyone is driving -- either commuting to or from work or heading out for their holiday that day.

Drivers sitting in traffic can take some comfort in the cost of gas. Most drivers will likely pay the lowest Memorial Day gas prices in at least five years. Today's national average price of regular gas is $2.73 per gallon, almost a buck less than the average price a year ago.

The obvious alternative for dodging highway madness is the airport. Uh, but maybe not on Friday. That day, according to the John Heimlich, chief economist for Airlines for America, will be 2015's third busiest day for air travel.

Staycation, anyone?

Contributing: Bart Jansen