More than 73,000 riders would use a Metrorail extension to Reston, and transit ridership in the corridor would increase 5 percent by 2025, according to a new report on the impact of the proposed line.

The preliminary study, which Metro made public last week, found that the largest category of users on the rail line, 23,500, would be reverse commuters from the District and its closest Virginia suburbs to jobs in Tysons Corner. The second largest number, 18,300, would be riders heading to downtown Washington; 14,700 would be going between Reston and Tysons; and the rest would be traveling to various destinations throughout the Metro system.

The new Metro line would add 11.6 miles and five stations, extending from the West Falls Church Station through Tysons Corner to Wiehle Avenue in Reston.

Virginia received permission in June to begin engineering work on the line, a necessary step before federal money can be allocated for the project.

Planners hope the extension is the first leg of a new line that stretches to Dulles International Airport, but local and federal funding for that portion is less clear.

The report aims to answer questions from some District members of the Metro board about whether the city would take an economic hit from the new rail line. A full report is due in January.

The study found that with the rail extension, regional bus and rail ridership on an average weekday would hit 960,000 in 2025 -- 45,000 more riders than without the rail line.

The 73,000 expected rail riders would make the five-station spur busier than the existing Yellow Line, which carries about 50,000 riders a day through Washington and Northern Virginia. The Red Line, Metro's busiest, carries about 237,000 riders a day, officials said.

Aside from ridership numbers, the study found that the rail line would be good for economic development in the transit corridor. By 2025, the report said, office development would be bolstered by 8 percent, retail by 4 percent and residential by 5 percent. Industrial development would dip by 1 percent.

Additionally, the study found that connecting Tysons Corner, the region's second-biggest job center, to the District would not hurt the city's high-end hotel industry, a concern of some Washington leaders. The study predicted that 500 rooms would be added and that "projected growth associated with Wiehle is not sufficient to challenge the District's dominance in the upper-tier hotel market."

The number of reverse commuters who would use the line highlights the growth of Tysons Corner. Business leaders in the booming area, filled with high-tech firms and government contractors, were one of the main forces behind extending rail into the corridor and came up with a funding plan to get it done.

"We're pleased that it's becoming a reality," said William D. Lecos, president and chief executive of the Fairfax County Chamber of Commerce. "It's already begun the process of stimulating the profound reevaluation of Tysons Corner and what it can mean in terms of managing growth in the region."

Lecos added that he hopes the line will invigorate the area with some of the day-and-night vibrancy that the Orange Line has brought to Arlington County.

In March, businesses in the Tysons area agreed to an increase in property taxes of as much as 22 cents per $100 of assessed value and eventually as much as 29 cents. Property owners now pay $1.16 per $100 of assessed value. There is a $400 million cap on the total amount that the tax increase can produce.

The general terms of financing the Metrorail line call for the federal government to pay half the cost. Virginia would raise 25 percent from a fare increase on the Dulles Toll Road, and the other 25 percent would come from Fairfax and Loudoun counties and the Metropolitan Washington Airports Authority.

The cost of the first phase of rail, to Wiehle Avenue, is estimated at $1.5 billion and the second phase, to Dulles, at $1.9 billion.