The upper passenger deck of the ferry Berkeley, now on exhibit at the San Diego Maritime Museum.

Launched in 1898, the double-ended steam-propelled Berkeley operated between the East Bay and San Francisco until 1958. It carried 1700 passengers on a 20-minute run across the Bay while consuming only 480 BTU of energy per passenger-mile.

Compare to single-occupancy cars at 7,000 BTU/mile or busses at 660 BTU/passenger-mile.

While modern fast ferries can be extremely energy-intensive, new designs have also been proposed that approach the efficiency of the historic low-speed steam configuration.

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