Local officials expressed surprise and concern yesterday after the Maryland transportation secretary's announced that the state is seriously considering a rapid bus system, instead of light rail, to run over the proposed Purple Line Metro route.

Robert L. Flanagan told members of Maryland's congressional delegation yesterday that a bus that runs on its own roadway from station to station might be a cheaper and more mobile alternative to rail. His announcement comes a week before the state is due to submit a list of transportation projects to the federal government for possible funding.

"I was totally blindsided by this," said Rep. Chris Van Hollen (D). "He raised the idea. And right now it's a totally undeveloped concept, with no details. We told him to come back when the idea is more fleshed out. At the last minute, this throws a whole new idea on the table."

"It kind of took me by surprise because I hadn't heard about it before," said Rep. Albert R. Wynn (D). "I think all of us want to talk to local officials and get their thoughts on it. . . . Previously, the Purple Line has been exclusively discussed in the context of light rail."

News of Flanagan's bus proposal stunned Montgomery County officials, who remain divided over what route the Purple Line, a proposed east-west Metro line between Bethesda and New Carrollton, would take through Montgomery County. Business and environmental groups and labor unions want the section between Bethesda and Silver Spring to run on light rail inside the Capital Beltway. Part of the route would follow an existing hiker-biker trail and would bisect the Columbia Country Club, which opposes the plan.

County Executive Douglas M. Duncan (D) favors a mostly underground line following a northern route outside the Capital Beltway. His plan would carry riders from the Medical Center Metro station near the National Institutes of Health, alongside the Beltway and then south into Silver Spring Metro station.

Duncan said yesterday that he was surprised by Flanagan's rapid bus idea and still stands behind his own proposal. "We need some kind of east-west connection in the county," Duncan said. "It's his [Gov. Robert L. Ehrlich Jr.'s] decision. I'm waiting to hear the decision, and we can move forward from there."

Bob Grow, who oversees transportation issues for the Greater Washington Board of Trade, said he was bewildered that Flanagan didn't mention a bus rapid transit Purple Line when he addressed the board's transportation and environment committee Wednesday. While Flanagan mentioned rapid bus transit as a cheaper alternative to rail with more flexible route options, he did not tell business leaders that the state was considering it for the Purple Line.

"It's never been brought up or floated," Grow said.

Wynn said Flanagan told the delegation that "no hard decision had been made" on whether the state would seek federal money for a rail or bus line and that there are ongoing discussions about whether the inner or outer route would be endorsed by Ehrlich.

In an interview, Flanagan said the bus system, which he described as a "super street train," would run on its own roadway or could be used on regular streets. Each car carries 130 people compared with the 270 people a standard rail car can hold, but each bus would cost $1 million while a typical light rail car costs $4 million, he said.

The engine would be a combination of diesel and electric and could eventually become an entirely electric system, he said. A weakness of the light rail proposal, Flanagan said, is that it would be limited to a single track for a stretch in Silver Spring, meaning that two trains could not pass each other at one time.

"We're thinking about different projects in a new way," Flanagan said. "We know there is a history of consumers preferring a light rail to traditional buses, but we'd like people to keep an open mind."

Staff writers Matthew Mosk and Katherine Shaver contributed to this report.

Transportation Secretary Robert L. Flanagan: "We're thinking about different projects in a new way."