Oklahoma City's Downtown Spirit Trolleys are hitting road.

Metro Transit authorities say after 13 years of service, the trolleys have reached the end of their economic life are are being retired.

They're being replaced by six new, 30-foot Downtown Discovery buses.

The new buses will offer free service in the downtown area, and will maintain the same route and schedule as the trolleys.

Metro Transit says the buses feature state-of-the-art emission systems which meet 2013 EPA mandates.

Downtown Spirit Trolley.