WASHINGTON - Advocates of "bus rapid transit" say the country is wasting billions of dollars to build glitzy urban rail systems when people can travel more cheaply and with less environmental impact by bus.

Bus rapid transit, or BRT, should not be confused with traditional urban bus systems, its most fervent advocates point out.

Instead of those smoky old mechanical dinosaurs that toil from stop to stop, BRT buses whiz along dedicated roadways, pausing briefly at stations where passengers quickly get on and off without having to pause and feed the driver's coin box.

New showcase systems in Los Angeles; Adelaide, Australia; Bogota, Colombia and other cities have been received enthusiastically by commuters.

In fact, Bogota's Transmileno is so popular that the mayor who built it, Enrique Penalosa, is often mentioned as a candidate for president.

But in Washington, BRT proponents say they are being out-lobbied.

In a report to Congress in February, the Federal Transit Administration said it planned to issue grants worth $18.2 billion to help build rail projects during fiscal 2008, and about $1.4 billion for BRT projects.

"The reason the federal government invests in rapid transit in the first place is that it gets people out of their cars," said William Vincent, a former Transportation Department official who is now general counsel of the Breakthrough Technologies Institute, a Washington-based environmental advocacy group.

"You cut down on greenhouse gases. You reduce oil consumption," Vincent said. "You can get the same number of people out of their cars for about one-quarter the cost with a BRT."

According to the institute's calculations, BRT can move commuters with less than a third of the carbon dioxide emissions of light rail, and one-sixth those of private cars.

When it comes to cost, Vincent recently studied federal documents surrounding the funding of 37 rapid transit plans.

Vincent said he found the annual operating cost for a rail system was about $933 per average weekday boarding.

That means if an average of 1,000 people board a system each weekday, the annual operating cost would be $933,000.

The average for BRT was less than half as much, $445.

Capital costs for rapid transit systems vary widely. For example, Boston's new Silver Line, a BRT that runs from South Station to Logan Airport, is costing more than $800 million per mile, Vincent said, and New York's Second Avenue Subway will cost $2 billion per mile.

But on average, he said, capital costs for the rail plans run $240 million per mile, compared with $66 million for BRTs.

According to the federal documents, "BRT seems to be the winning option," he said.

So why the disconnect between cost and federal funding?

"To be quite blunt about it, there's a lot more money to be made building rail systems than there is building BRT systems," he said. "So you have major engineering and construction firms lobbying cities to build rail so they can make more money."

In addition to the local preference for rail systems, the federal transit agency is hamstrung by congressional earmarks in its budget.

In a recent transportation spending authorization, Congress wrote in more than 6,000 earmarks, mandating federal support for everything from safety gates at remote rail crossings to elaborate ferry docks and other transportation infrastructure.

Among rapid transit systems, the congressional earmarks overwhelmingly favored rail, although there were also BRT earmarks, including a $100 million authorization for a system in Birmingham, Ala.

The American Public Transit Association, made up of government transportation agencies and private industry, also favors light- and heavy-rail transportation systems.

Vincent's enthusiasm for the bus systems is not shared by everyone who would use them.

Ross Capon, executive director of the National Association of Rail Passengers, said buses were slower, carried fewer passengers and were sometimes dangerous.

Also, he said, "evidence has proven conclusively" that claims of superior cost-effectiveness of BRTs "have been overstated." Similar preferences were noted in a Government Accountability Office report three years ago to the Senate Banking, Housing and Urban Affairs Committee.

Although GAO official JayEtta Z. Hecker concluded that BRTs offered many advantages in terms of cost and flexibility, she concluded that "bus service has a negative image, particularly when compared with rail service."

She said rail-based plans were often viewed as the mark of "a world-class city" and an image-enhancer that could attract developers.

"As more experience is gained with BRT, its advantages and disadvantages will become better understood," she said.

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