A committee of top Northern Virginia officials adopted a $30 billion plan last night for expanding roads and transit that includes a last-minute amendment designed to screen out projects that would promote sprawl.

The clause assuaged officials from Arlington County, Alexandria and Falls Church who had threatened to rupture the consensus that had developed over the 20-year plan because of objections to a proposed Western bypass outside the Capital Beltway and two new Potomac River bridges added within the final week.

In adopting the plan with only one dissenting vote, the Transportation Coordinating Council (TCC) outlined a regional vision that includes not only the bypass and bridges but also 87 new miles of rail.

"The TCC's approval of the 2020 plan is the most important transportation initiative ever taken by elected officials in Northern Virginia," said Fairfax City Mayor John Mason, vice chairman of the panel. "We must now work with the General Assembly and governor to develop an assured funding source to make it happen."

That task is crucial because the cost is $14 billion higher than the sum now planned for the region and none of the funding proposals offered in recent months by Gov. James S. Gilmore III (R) and state legislators has come close to closing that gap.

That means the projects approved last night could remain little more than a wish list. Some of the proposed projects face other obstacles, including Maryland's objections to Virginia's proposals for new bridges across the Potomac and objections from federal regulators to the Western bypass.

Some TCC members also expect that several contentious road projects ultimately could be vetoed under the terms of the anti-sprawl amendment approved last night. This clause requires projects to be evaluated according to whether they encourage a reduction in automobile use, support rail and bus service and encourage development in established communities.

"There's a whole bunch of things in here that more closely tie transportation and land use than have ever been adopted by a regional body," said Arlington County board member Chris Zimmerman (D).

The amendment made it possible for Zimmerman and several other TCC members to accept the 20-year plan after it had been expanded by $4 billion, following aggressive lobbying by the business community, to include the bypass and bridges. Earlier this week, it had seemed that these additions would fracture the unusual consensus that TCC Chairman Kenneth Klinge had crafted over the last two years.

"This is an aggressive, balanced, multimodal plan that is essential to ensure our continued economic growth and quality of life for families in our region," said Klinge, of Alexandria.

Among the major projects included in the plan are improvements to more than a dozen highways and the construction of a Tri-County Parkway west of Route 28 and a Route 234 bypass north of Interstate 66.

One of the proposed bridges would link Interstate 95 in Prince William or Stafford counties to Route 301 in Southern Maryland. The other would connect the Western bypass, running from Stafford to Loudoun County, with Interstate 270.

The proposed train projects include extending Metrorail through Tysons Corner to Dulles International Airport and adding new Metro lines to Centreville, the Potomac Mills area and from Dunn Loring to Maryland. Light rail service, similar to trolleys, also would be added along Routes 1, 28 and Columbia Pike.