Marin County Supervisors on Tuesday voted to hold a merit hearing for a proposed ordinance that will ban larger-sized vehicles on certain county roads. Under the ordinance, vehicles longer than 36 feet will be prohibited from driving on some roads. The ordinance responds to complaints from Muir Beach residents who say tour buses passing through residential neighborhoods on their way to Muir Woods—the county’s most popular tourist destination—pose safety risks. But many in Muir Beach…