The Southeast Michigan Regional Transportation Authority Act would establish the transit authority for Macomb, Oakland, Washtenaw and Wayne counties.
The bills approved Tuesday still must pass the House before going to Gov. Rick Snyder for signature.
An authority could accept federal funding for transportation projects, notably the proposed M-1 high-speed passenger rail system along Woodward Avenue from downtown Detroit to the city's New Center area.
Business leaders have said they've raised most of the funds to get the project going.
Routes under an authority may include Woodward between Detroit and Birmingham; along Gratiot from Detroit to Mount Clemens; between Troy and Mount Clemens; and from Detroit to Ann Arbor.