DENVER --- Colorado Gov. Bill Ritter is launching a plan to reduce petroleum usage in state vehicles 25 percent by June 2012. According to the Denver Gazette newspaper, Colorado state officials are exploring a number of ways to reach this goal, including replacing the fleet with green vehicles, decreasing the size of the fleet, limiting miles driven, and providing incentives for state employees to take mass transit for their commutes. During the fiscal year that concluded June 30, the state purchased 192 flex-fuel vehicles. This represented a sizable chunk of the 780 state vehicles purchased overall in the fiscal year. The state fleet also currently includes 50 hybrid electric cars and 286 diesel-powered trucks that can operate on B-20 biofuel. The state's fleet uses 4.3 million gallons of fuel annually. It's not clear what percentage of that total is alternative fuel, however.