SAN FRANCISCO City officials here are cracking down on tour buses parking and stopping illegally near famed Lombard Street, "the crookedest street in the world."

Mike Waters, general manager of Franciscan Lines and a director of the California Bus Association, said he had been asked by the head of the city department of parking and traffic to get the word out about "asking tour buses NOT to park anywhere on Mason Street near the bottom of Lombard Street.

"Ticketing for parking here (is being) aggressively enforced," said Waters. "Any out-of-town bus attempting to give their passengers a view of Lombard Street should park in the white zone in front of 1075 Columbus Avenue (Bimbos 365 Club), and have their passengers walk the two blocks to the bottom of Lombard Street," Waters said.

Neighborhood residents reportedly have complained to the city council, and were attempting to make the area off limits to buses because of the carelessness shown by a number of tour bus companies.

Lombard Street is best known for a one-way section on Russian Hill, between Hyde and Leavenworth streets, in which the roadway has eight sharp turns (or switchbacks) that long-ago earned it the distinction of being called "the crookedest [most winding] street in the world."

The switchbacks design, instituted in 1922, was created to reduce the hills steep grade, which was too severe for most vehicles to climb. It also is a serious challenge to pedestrians.

The crooked section of the street, which is about a quarter-mile long, is reserved for one-way traffic traveling east (downhill) and is paved with red bricks. The speed limit is 5 mph.

A decade ago, a Crooked Street Task Force was created to try to solve traffic problems in the neighborhoods around the winding section of Lombard Street. In 2001, the task force decided it would not be legal to permanently close the block to vehicular traffic. Instead, the task force decided to institute a summer parking ban in the area, to bar eastbound traffic on major holidays, and to increase fines for parking in the area.

One city transportation manager told Waters in an e-mail that tour buses should not park alongside the barricades on Mason Street at Lombard Street, and at Mason Street at Columbus Avenue.

He said the neighbors and the San Francisco Fire Department were "irate about this," and the official had instructed the city enforcement division "to cite these illegally parked buses aggressively.

"These are the same neighbors who want to prohibit tour buses on Mason and Powell streets," said the official.

It is OK for tour buses to park in the white zone in front of Bimbos 365 Club on the west side of the 1000 block of Columbus Avenue (between Francisco and Chestnut streets) while Bimbos is closed, which is usually the case during the daytime.

"You might also remind them that idling their engines for more than five minutes is a violation," the official added.

Welcome to San Francisco.