The jet set of the world may swear by its Concordes, and subway fans may marvel at a BART or Metro. But commuters in this area have their transit hopes and money riding on the "Tijuana Trolley."

That's not the formal name of their streetcar desire, but neither is it some old buff's idea of a nostalgic trip for tourists. In today's megabuck era of swift and sleek transportation, it is one region's low-budget adaptation of yesteryear's ideas for tomorrow's mass-movement traffic between San Diego to the north and the border with Mexico to the south.

If people laughed at Robert Fulton and his steamboat, there were more than a few snorts and snickers here a few years ago when the newly created Metropolitan Transit Development Board concluded that the best and most economical system for their fast-growing commuter corridor would be a set of trolleys.

In the stiff-syllabled jargon of transportation's professional movers and shakers, you don't say trolley, though; it's electrically propelled light rail transit," which offers "some hedge against a growing population, increasingly congested freeways, dwindling energy supplies and unknown future restrictions on the use of the automobile."

It also happens to get around one more restriction that has sent so many transit planners up the wall in other regions: Uncle Sam. Because no federal money is involved, this project has no elaborate, time-consuming federal requirements, studies, justifications, applications, labor agreements, approvals or quadruplicate copies that have a way of bogging down progress while shooting up costs. "You burn years just doing all that," says one official.

Total cost for this 16-mile link, which is scheduled to open a year from now, is pegged at $86 million. Most of this -- about 88 percent -- is coming from a California state gasoline tax and the rest from proceeds of a 1/4-percent sales tax.

Transit board officials hasten to note that the absence of federal requirements doesn't mean that a system is unsafe at any speed. Instead of going through a federal environmental impact statement, this project is being built to California Environmental Quality Act specifications and other tests that they say meet the same standards with far less fuss or budget.

They're not talking about antique trolleys, either. There will be 14 modern "articulated" cars -- those are the ones that are hinged with accordions -- that can carry up to 400 passengers in one two-car hookup. With overhead wiring, they will run through downtown San Diego on tracks being built to connect with a 108-mile existing railroad right-of-way that was bought from the San Diego & Arizona Eastern Railway for a relative song in today's market -- $18.1 million.

Any subway users in other cities who have been frustrated by backups in their subways because of fare-card collection barriers will be interested to know that the San Diego line will rely on an old-fashioned fare system. Instead of lining up at one door or gate and feeding coins or tickets into balky collction machines or boxes, riders who have tickets can hop on the cars through any doors; roaming inspectors will make spot-checks. "Don't call it an honor system," a board spokesman cautions, "because there won't be any honor -- we're going to be checking. It's just cheaper this way."

Once cars leave downtown San Diego, average speeds will be 35 to 40 miles an hour for the rest of the 16-mile trip to San Ysidro, 300 feet this side of the border. With 11 stops in all, the complete ride should take about 38 minutes. As many as 20,000 daily passengers are expected at first, growing to at least 30,000 by 1995. These estimates were made when gasoline was selling at 40 cents a gallon -- so there may be a few more trolley fans than planners thought.

Even now, without the line, traffic up and down the corridor is heavy. Mexicans spend an estimated $407 million in the San Diego area each year while Americans spend about $660 million in and around Tijuana. About 95,000 crossings at the San Ysidro-Tijuana border are clocked each day by workers, shoppers and travelers.

Though planners figure that their line will cost less per mile to run than buses, subways or any other combinations, they don't pretend that trolleys are the perfect answer for all cities. But from everything they've learned so far, the kinds of streetcars now on line for use here next year may well be considered rolling stock -- rather than laughing stock -- in more than a few urban centers in the future.