Construction on a long-awaited pedestrian and bicycle bridge over Route 7 in west Falls Church has begun and, weather cooperating, is expected to be completed in about two months. The two-span, $900,000 overpass will provide safe passage above the busy, four-lane thoroughfare for users of the Washington & Old Dominion Trail.

"This is going to provide 100 percent safety. It will be uncompromised safety to all the trail users," said Craig Day, a founder and vice president of Friends of the W&OD Trail.

Currently, trail users must battle four lanes of traffic or detour about one block east of the trail to cross Route 7 at a traffic light. The new bridge is the 16th overpass built by the Northern Virginia Regional Park Authority along the 45-mile trail and will address one of its nagging worries.

The Route 7 crossing "is one of the major areas that we were concerned with. . . . Our major long-term objective is safety," said the authority's executive director, Darrell G. Winslow. "Every time they build a highway {that crosses the trail}, we'd like to make sure there is a separate crossing" for pedestrians and bicyclists.

"There have been a number of accidents but no deaths {at the Route 7 crossing}. But we've been lucky that nothing {worse} has happened," said Day, whose group is raising funds for the project. "Our bottom line is to protect and improve the trail for all users. We want to make sure the trail stays safe and works for everyone."

Recently, a pedestrian bridge was completed in Herndon. Other bridges in Loudoun and Fairfax counties allow trail users to safely traverse streams and busy streets. According to Winslow, when a separate crossing is not possible at intersections, the park authority tries to improve safety by providing traffic lights or designated crossing areas.

The Falls Church project is expected to cost about $900,000, of which $650,000 was provided by the park authority, the City of Falls Church, the state and private and corporate sponsors.

The remaining $250,000 was advanced by the park authority last September to save money and limit inconvenience by allowing the project to be coordinated with the Route 7 improvement project that is now underway. The Friends of the W&OD Trail will pay the money back through its fund-raising efforts. With about 500 memberships and through contributions and the sale of T-shirts, about $24,000 has been raised.

"They've been extremely beneficial to the park authority, and not only through raising funds," Winslow said of the friends group, which produces a trail newsletter, provides an information hot line, lobbies for improvements and organizes events. "But they've also helped us get support and all kinds of other {positive} things."

Concrete supports for the overpass were built this year as part of the Route 7 renovation. Last week, the divided, 16-foot-wide, 390-foot-long bridge arrived at the site in 16 prefabricated pieces. Erection of the bridge over the road, which will take place between the morning and evening rush hours to limit traffic disturbance, is expected to take about 10 days. Unless delayed by poor weather, the ramps, asphalt surfacing, fencing and other finishing items should be completed in six to eight weeks, officials said.

"What will be such a wonderful feeling will be to stand below {the bridge} and just watch people go across," Day said. "That will be a very satisfying day."