Public transportation in Tacoma includes buses, commuter rail, light rail, and ferries. Public bus service is provided by Pierce Transit, which serves Tacoma and Pierce County. Pierce Transit operates 43 bus routes (five of which through Sound Transit), using a fleet of buses powered by compressed natural gas, diesel, and electric batteries. Bus service operates at 30–60 minute frequencies daily, while three heavily ridden "trunk" routes are mostly served every 20 minutes on weekdays and every half-hour to an hour on weekends as of October 2, 2011. The bus route serving the Pacific Avenue corridor is planned to be upgraded into a bus rapid transit line by 2022, at a cost of $150 million.