MANCHESTER, Tenn. (AP) -- With the Bonnaroo music festival opening Thursday, law enforcement will be drawing on seven years of experience in dealing with the crowds and traffic.

The four-day outdoor festival swells the population of Manchester from less than 10,000 to potentially more than 100,000.

State transportation officials say improved traffic control over the last couple of years may help to change the festival's reputation for monumental traffic jams.

But Tennessee Highway Patrol spokesman Mike Browning says the high cost of gas this year could mean more stuck cars that run out of gas while waiting in line.

The heat also could be a problem, as it has been in years past, but a line of showers and thunderstorms is expected to cool down the high temperatures to the mid-80s by the weekend.

(Copyright 2008 by The Associated Press. All Rights Reserved.)