Click image for enlargement. Graphic by Mike Johnson.

How fans get to the Las Vegas Motor Speedway for NASCAR weekend may be of less concern to race officials than at what time they go.

While event traffic control has improved in recent years, a schedule change and the start of daylight-saving time during the March 9-11 event means fans will have to adjust their routines accordingly.

"We're throwing one more wrinkle at the race fans this year," Chris Powell, speedway general manager, said Wednesday before joking, "We just want to make sure everybody's paying attention."

The Sam's Town 300 on March 10 will start at noon, 3 1/2 hours earlier than last year's race. And while the weekend's premiere event -- the UAW-DaimlerChrysler 400 on March 11 -- will retain its usual 1:30 p.m. start time, that will be the first day of daylight-saving time, with clocks moved ahead one hour.

Still, most of last year's traffic plan remains in place to handle as many as 157,000 fans and about 40,000 cars, trucks and RVs expected each day of the event.

"Things have worked very well," Powell said. "Each year, we tweak here and we tweak there. For the most part, things are the same as in 2006."

One of those tweaks will be the use of highway shoulders as traffic lanes on some portions of Interstate 15 near the speedway. Signs will indicate in what areas shoulder driving will be allowed, Powell said.

Most race fans are expected to use I-15 to get to the speedway, in the far northeast valley. Local fans coming from the northwest or southwest are being asked to take the Las Vegas Beltway to the track, while fans from the northeast and southeast can consider Las Vegas Boulevard.

During the three-day weekend, which includes qualifying races on March 9, gates will open no later than 8 a.m. each day, with races letting out no later than about 4:45 p.m.

The races, in their ninth year here, have been viewed with caution by local drivers since a 1999 traffic meltdown that left some racing fans stuck in parking lots for as long as five hours after the event.

As authorities have gotten better at anticipating race-day traffic and fans have become accustomed to getting to and from the track, those problems have ebbed in recent years.

"I'd like to say it's certainly improved every year," said Jeff Motley, a speedway spokesman. "We're getting more and more repeat visitors. They become more educated on various ways in and out of the facility."

Still, congestion is expected because of the size of the event, which organizers call the nation's largest sports gathering west of Texas. Drivers are being urged to arrive early, leave late and expect slowdowns.

"Coming in they spread themselves out over a six-hour period. Leaving the facility, everybody jumps behind the wheel and wants to leave now," said trooper Kevin Honea of the Nevada Highway Patrol. "It's not possible. Just be patient."

Locals are being asked to car pool or take shuttle buses.

On race days, speedway officials plan to provide updated traffic and parking information every 15 minutes or so on KKLZ radio at 96.3 FM.

Basic traffic and parking information will be provided via a Nevada Department of Transportation advisory radio station at 1610 AM.

Citizens Area Transit plans to provide shuttle bus service to and from the Strip and downtown Las Vegas. Pickup locations on the Strip include the Aladdin/Planet Hollywood, Flamingo, MGM Grand, Paris, Riviera, Tropicana, the Venetian, Luxor and Stratosphere, outside the Sahara monorail station and at the South Strip Transfer Terminal.

Downtown pickups will be at the Downtown Transportation Center and the corner of Fourth and Fremont streets.

The speedway and one of its sponsors will cover the cost for Designated Drivers Inc. to drive drunken fans home in their own cars, upon request and for no charge.