When Thomson Hirst was in grade school, his father sometimes took him to work. Omer Hirst was a member of the House of Delegates from Fairfax County.

"The House of Delegates used to allow us to bring our children onto the floor," the elder Hirst recalled from his home in Florida recently, "and the pages would bring an extra chair for them to sit next to us. He [Thomson] liked that. He was always interested in public affairs."

Omer Hirst, a Democrat who later served 14 years in the state senate, is perhaps remembered most for his fight against segregated schools in Virginia in the 1950s. His was a lonely and unpopular stance but one that ultimately prevailed.

His son was greatly influenced by his father.

"Speaking out against the continuing practice of segregating schools didn't make him very popular," the younger Hirst said. "My family has a strong tradition that when the fix is in and something is wrong, to try to fix it, correct it, reform it, you might say."

Now Thomson Hirst, 60, is in the middle of his own battle. He is leading the fight against extending rail service to Tysons Corner and Dulles International Airport.

Hirst is advocating a bus rapid transit system. He said the bus system would save billions of dollars, carry just as many people as trains and could be running within two years instead of the seven or more years it would take to build rail.

The 17-member Commonwealth Transportation Board, which oversees state highway and transit projects, announced its support in December for the $4 billion, 24-mile rail project connecting Metro to Tysons Corner and Dulles. The Fairfax County Board of Supervisors and Metro also back the project, as does nearly every civic, political and business organization along the corridor.

The Federal Transit Administration has said that it will not recommend that the rail project receive federal funding unless local officials scale it back to a rail line to Tysons and express buses to the airport. That has not deterred the pro-rail lobby, however.

Hirst, a Reston resident, is president of Rapid Transit Action Committee and is trying to derail the project, despite knowing success is a long shot.

"He is the saint of lost causes," joked Bill Vincent, who was director of the U.S. Department of Transportation's policy office during the Clinton administration. Vincent is general counsel for Washington-based Breakthrough Technologies Institute, a nonprofit organization that promotes new energy and environmental technologies, and he is working with Hirst to promote the bus rapid transit system.

"Tom is very passionate, and he is very smart, and he believes very strongly in what he is doing," Vincent said. "He is very courageous and trying to be the voice of common sense and rationality, taking on a system based on pork politics and backroom dealing."

Hirst is president of Mason Hirst, a real estate and development company founded by his grandfather, T. Mason Hirst, in 1921. Hirst can trace his family lineage back to George Mason. His grandfather was a cattle rancher in Fairfax County as well as a real estate broker.

His grandfather's cattle ranch was cut in half by construction of the Capital Beltway.

"I had worked on my granddad's farm in the summers," Hirst said, "and when I went away for college, they were working on the Beltway. And when I came back home for Thanksgiving, they were building [the Route 236] interchange at my family farm, and everything just radically changed for me and what I was interested in."

Hirst returned to Princeton after Thanksgiving break and began studying city and regional planning. He went on to get a graduate degree at Harvard University. "My experience at Harvard gave me exposure to the top brains of transportation planning," he said.

Hirst, with his two Ivy League degrees on his wall, still remembers fondly the advice from his grandfather, who had a sixth-grade education. "Tommy," his grandfather used to tell him, "what you want to do is get in the way of progress and let it run over you."

For the past year, Hirst has been trying to get in the way of the rail extension project.

"This is just the sort of issue that tends to grab you and won't let you go," he said. "You wake up at night thinking about it, just can't get it out of your head. It is such an exciting technology, and it is so exciting to be dealing with such an important, urgent problem and have what you think is the correct answer."

The correct answer, for him, is a bus system first developed in Brazil and being used on a limited basis in Los Angeles. Other cities, including Miami, Pittsburgh, Seattle, Phoenix and Hartford, have variations of the same system.

Bus rapid transit, or BRT, uses specially designed buses that operate in exclusive lanes, created on existing roads, and can carry as many as 270 people. The buses are equipped with radio signal devices that control traffic lights, so the light is always green for an approaching bus. The buses have multiple doors that open with a ramp to the bus station platform, which makes them handicapped-accessible.

The BRT system, according to Metro and state officials, would cost about $481 million, though Hirst thinks it could be built for about half that amount.

He said economics will eventually kill the rail project.

"The thing that is absolutely certain -- and I will bet my life savings on -- is that there is no way that rail will actually ever get built," Hirst said, citing the high costs. "It is just a matter of time before people acknowledge that it is a non-starter. Once they acknowledge that, they will turn to BRT. My goal is to stop the wasteful expenditure of tens of millions of dollars each year on studies and stop the waste of time and to actually bring service to the people right now. Start thinking in terms of months rather than years."

Hirst and Vincent know they will have a tough job building momentum for their alternative plan.

"The political momentum around the project is so intense, it it is hard to slow down," Vincent said. "I think what ultimately will drive it is that there is no money for a rail project and, sooner or later, that cold, hard reality is going to hit home."

At least one politician, U.S. Rep. Frank R. Wolf (R-Va.), is trying to make the same point with local officials who endorse rail. Wolf, a member of the transportation subcommittee of the House Appropriations Committee, said it is unlikely that Congress would authorize enough money to build rail to Dulles by 2010.

A more realistic approach, he said, is to extend Metrorail to Tysons with "modern, efficient buses with laptop connections" carrying riders between Tysons and the airport. When the money is there, Wolf said, finish rail to Dulles -- probably by 2020.

Hirst has a video, which he will show to anyone willing to watch, about how the bus rapid transit system, also known as busways, has worked in Los Angeles.

The Los Angeles Metropolitan Transit Administration announced in December a 24-line, 356-mile expansion of BRT service. Since introducing the service along the Wilshire and Ventura Boulevard corridors in 2000, ridership has increased 40 percent, according to the authority. About 55,000 people use the service daily.

"Metro service [BRT] has been a huge success story in Los Angeles and has generated considerable interest from other large cities that are trying to grapple with congestion," L.A. Mayor James Hahn said when the expansion was announced.

Hirst said if it can work in Los Angeles, it can work here.

He said BRT could initially run between West Falls Church and Tysons using Interstate 66, Route 123 and Route 7, before connecting to the Dulles Airport Access Road, and then on to the airport. Eventually, Hirst said, if BRT is successful it could be expanded into Maryland and have feeder routes running through neighborhoods so that commuters would not have come to a station; they could leave their cars at home.

Hirst talks about the project with great passion. He is fighting against the tide, but he said that feels natural because it is in his genes.

"My father and my mother pretty much taught me to think outside the box," Hirst said, "to look at a problem and step back and take a viewpoint and to be very practical."

His father was a practical politician. He and another Democratic state senator proposed building the Dulles Toll Road, whose formal but little-used name is the Omer L. Hirst-Adelard L. Brault Expressway, and found a way to build it. "When you don't have money, you borrow it," former senator Hirst, now 90, said. "We borrowed it and used to the tolls to pay it back."

It was a practical solution to the problem. His son has a practical solution to his project: Get Gov. Mark R. Warner (D) behind it.

"In Virginia the governor controls the money," Hirst said. "It is exactly the kind of system he should grab and run with. It has innovative technology, takes very limited resources. It is a system that can be up and operational before he leaves office. It is the one place where, despite the shortage of funds, he could make a really dramatic statement and have national prominence overnight because transportation is an issue throughout the country."

He has not spoken to Warner about it but said that he could make his case if he could get half an hour. The governor has consistently backed rail to Dulles.

Hirst is fighting an uphill battle, he knows. He is full of passion and impatience for change.

What he is proposing is out of the mainstream and not in step with the will of the politicians, but he believes in what he is doing and, sitting at his father's knee in the Assembly, he learned to stand up for what he believed.

"When I started this, everybody said, 'Tom, the fix is in, don't bother trying to stop this. It is going through, there is nothing you can do about it,' " he said. "And it seemed to me it was wrong, what was happening. And I guess I've taken a fair amount of personal and political risk, but we will take our chances."

Thomson Hirst, pictured at the Wiehle Avenue Park and Ride station last month, is leading a very small minority pushing for rapid bus service in the Dulles corridor instead of a rail line. He says the bus system would save billions of dollars, carry just as many people as trains and could be running within two years.Thomson Hirst's father, Omer, who served as a state delegate and senator, was instrumental in building the Dulles Toll Road. He is perhaps best known for fighting segregation of Virginia schools in the 1950s.