Traffic that snarled Highway 101 last week from Santa Rosa to south of Petaluma for the opening of the Graton Resort & Casino in Rohnert Park seems to have leveled off, the CHP said Sunday.

"It's not as bad as we expected," CHP Officer Nenad Gorenec said.

Central Rohnert Park was congested overnight Saturday from 10 p.m. to 2a.m. Sunday as folks flocked to the largest casino in the Bay Area on its first weekend night. But no major problems or roadway backups were reported.

Two minor collisions were reported Saturday on 101, one in each direction, near the Golf Course Drive exit to the gambling hall. One was suspected to be alcohol-related, Gorenec said. No one was hurt in either collision.

Sunday, traffic was free-flowing with only slightly heavier than usual traffic, drivers reported.

That was a far cry from Tuesday morning as the $800 million casino opened its doors for the first time to thousands of gamblers who came from all over the Bay Area to drop cash into the 3,000 slot machines, play card games and try the new restaurants and bars inside the 340,000-square-foot complex.

Three hours after it opened, solid traffic stretched as far as 24 miles south of Rohnert Park, the CHP said. An electronic sign in Novato warned drivers that it would take an hour to travel the 22 miles to the casino. City streets and back roads around the casino were just as jammed as drivers sought relief or shortcuts.

The surprise arrival of about 75 unscheduled tour buses added to the opening day's customer gridlock, as crowds were so thick at times they were let in a few at a time. Inside, more than 5,000gamblers tried their luck on the Las Vegas-style casino floor.

Expecting an onslaught of unknown proportions, the CHP, Sonoma County Sheriff's office, and Rohnert Park and Petaluma police all ramped up staffing to handle traffic nightmares. By late Tuesday, some frustrated drivers resorted to calling 911 to report they couldn't get out of the casino because of the crush of vehicles.

The CHP continues to have additional patrol cars and motorcycle officers on duty.

"We'll have them on through tonight," Gorenec said, "then we'll see, as needed."

Patience remains the word of the day for drivers headed anywhere near the casino.

"It's just so new. People need time to get used to it," he said.

The casino is open 24 hours a day.

You can reach Staff Writer Lori A. Carter at 762-7297 or lori.carter