LOS ANGELES — This is the place where food trucks really first took to the streets, catering to fanatical customers who relished — along with the food — the renegade and slightly outlaw nature of the whole business.

Those frontier days may be about to end.

Los Angeles County is moving to submit its flock of 9,500 food trucks and carts to the same health department rules as restaurants — including requiring them to prominently post a letter grade based on food inspections — in what may be the ultimate sign that this faddiest of food fads is going mainstream. And if that is not establishment enough, food trucks, whose allure has been enhanced by their mysterious comings and goings, some signaled by puffs of Twitter postings, will have to file route maps (route maps!) with the health department, to facilitate at least one field inspection a year, beyond the single annual inspection now required.

As with restaurants, health inspectors will be empowered to shut down a truck that scores less than a C.

“People are saying, ‘I see A, B, C’s at restaurants, but not trucks: Why not?”’ said Jonathan E. Fielding, director of the Los Angeles County Department of Public Health.

He said Los Angeles had seen a 13 percent reduction in hospitalizations linked to restaurant food poisoning since the county first imposed the rule on restaurants in 1997.

“We changed the incentives, and that’s what this is all about,” he said. “We want protecting consumers against food-borne illness to be top-of-mind all the time.”

By any measure, this is a serious moment in the evolution of food trucks, coming in the city that is the symbol of the Wild West ethos of the trucks: Where it is possible to walk the streets and face an array of offerings ranging from traditional beef tacos to kimchi quesadillas (think Korean-Mexican fusion), sold in trucks painted in pastel colors, affixed with Twitter addresses. They draw rolling throngs of customers whose nonchalance at the prospect of these new regulations, at least as reflected in some interviews, suggests that the dietary risks of food truck exploration might actually be part of the thrill.

“Sometimes I get a kick out of eating where it doesn’t look like it’s the cleanest,” said Joel Micallef, 37. “You can imagine the underbelly is full of cockroaches. But I bet some restaurants that get A’s probably have some problems you can’t see.”

But Deborah Beckman, 35, who visits the trucks every day, said she would pay close notice to any posted grade, as she did at restaurants.

“I’ve never eaten at a C restaurant,” she said. “I feel sketchy eating at a B.”

Los Angeles is one of a growing number of cities trying to accommodate an explosion in the number of food trucks. The health regulations to be voted on by the Los Angeles County Board of Supervisors on Tuesday appear to be among the most exacting in the nation, further erasing the line between how restaurants and food trucks are treated, and signaling a new phase in regulation that until now had been focused on where they can park and for how long.

(One of the biggest changes proposed to the Los Angeles County Code: The phrase “food establishment” is replaced throughout with the words “food facility.”)

In Chicago, the City Council is considering legislation to open the gates for food trucks by removing a restriction on cooking on the road; under current law, trucks are allowed to sell only prepackaged foods. Central to any deal, officials said, is that the trucks agree to be subjected to regular health department inspectors, and that they file their routes so inspectors can find them.

All of this is more than fine with the food truck operators.

“Very much so,” said Matt Maroni, an operator in Chicago who has been pushing for the change. “We’re not fighting anything; we just want to be allowed to do it.”

Lawmakers in Austin, Texas, where the number of trucks has been increasing 20 percent a year since 2006, just toughened its regulations by requiring owners to file their routes with the city. And in a reflection of this new reality, the City Council authorized the hiring of three new inspectors.

“We needed more compliance,” said David B. Lopez, manager of the environment and consumer health unit of the Austin/Travis County Health and Human Services Department. “And we need more staff to do this compliance.”

New York City requires food trucks and carts to get permits and subjects them to annual inspections, city officials said. But New York imposes a strict cap on the number of food carts, issuing just 3,100 two-year permits and 1,000 seasonal permits; there is a waiting list, officials said.

The food truck industry in Los Angeles has not resisted this latest regulatory incursion, in contrast to previous efforts to limit where they could park. For one thing, some proprietors said, it would probably not be wise to appear to be resisting routine health inspections. And posting a letter grade, assuming it was a passing grade, would presumably be good for business.

“It brings more legitimacy to an industry that is fairly new in the mainstream,” said Matt Geller, vice president of the Southern California Mobile Food Vendors Association, which represents 86 food trucks. “It couldn’t come soon enough for us.”

Gloria Molina, a member of the Board of Supervisors, and one of the backers of the measure, said: “It’s very hard to say, ‘No, we shouldn’t be inspected.’ They are providing food to consumers, just like restaurants.

”Everyone is going to support it — until they get a B or a C,“ she continued. ”And than they are going to be opposed to it.“

Still some food truck operators expressed worry that the government, in protecting the interests of restaurants, would use these regulations to try to hound them out of business.

”It’s good to have letter grades, but I don’t think they have our interests at heart,“ said Vince Giangrande, owner of the Vesuvio truck on Wilshire Boulevard. ”It’s another way to put us out of business.“

And several said this could be particularly troublesome for old-school Latino taco truck operators, who might not speak English and thus would have trouble dealing with inspectors who do not speak Spanish.

”My main concern is not the ordinance itself but the treatment of the vendors by the inspectors,“ said Erin Glenn, executive director of the Asociacion de Loncheros La Familia Unida de CA, which represents many traditional taco trucks. ”Oftentimes, with traditional food trucks, there is a language divide. Truthfully, this could be such a challenge for some of our members.“

© 2010 The New York Times Company