WASHINGTON (Reuters) - Two U.S. Senate Democrats on Tuesday proposed spending $73 billion to electrify the nation’s 70,000 transit buses as part of a push to move the United States toward zero-emission transportation. U.S. Senate Majority Leader Chuck Schumer and Senate Banking chairman Sherrod Brown noted only 2% of U.S. buses are zero-emission vehicles. They propose using funds to electrify transit vans and other vehicles and requiring all vehicles purchased using the funds are made in the United States. Reporting by David Shepardson; Editing by Chris Reese Our Standards: The Thomson Reuters Trust Principles.