Montgomery County doesn't have the development to support a proposed $1.8 billion bus system and might not for 30 years, county Planning Department staff said Thursday.

"[The county executive's Transit Task Force]'s plan calls for building the entire network in the next nine to [20] years, but that puts completion 30-40 years ahead of some of the intended development," planning staff wrote in an analysis.

As a result, taxpayers could be paying for bus rapid transit -- or BRT -- while empty buses operate on many of the proposed 160 miles, said Master Planner Larry Cole.

The Transit Task Force in a report last week suggested paying both construction and operating costs using property tax revenue. Residents could face as much as a 15 percent increase in property taxes under the proposal.

Normally the county asks developers to help pay for necessary transportation projects, like in White Flint where new developments have spurred plans for major changes to Rockville Pike. "If you build all of that stuff before the developers even show up, the public bears all of that cost," Cole said. "You don't want to build something no one is going to use."

The Planning Department has three options, Cole said: cut back on planned road improvements, reduce the size of the proposed bus network or increase density around the proposed transit system to support it.

But the department has the wrong idea, said County Councilman Marc Elrich, D-at large, who brought the idea of BRT to the county. The goal is not increasing development, but rather reducing congestion.

"If you live in Glenmont or Olney or the whole east side of the county and you want to get to the west side of the county ... you can't do that in a reasonable amount of time," he said. "This is about moving the people from where they live to where they work."

He pointed to Connecticut Avenue, a corridor the department is considering eliminating because it doesn't have the density necessary for the system.

"Connecticut Avenue backs up from [East-West Highway] all the way to the Beltway," he said. "It's not that there's density there. It's to get the cars off."

Still, some planned routes might be unnecessary, said County Councilwoman Nancy Floreen, D-at large, and chairwoman of the county's Planning, Housing and Economic Development Committee. Though the county has done studies showing the impact BRT will have along the I-270 corridor -- where Johns Hopkins University has planned a research campus -- many corridors have not been studied.

"You've got to be realistic about what is fundable and what is doable and where the demand is," she said. "We have to be real careful about going ahead full steam with this."