To be sure, the Servell-Munson cycle. Too bad the thermodynamic efficiency is only about 12-18 %. Plus all that fuel from corporations with abusive business models. Cheaper in the long run to run a diesel engine based system.
And age and physical fitness. I can ride maybe 2 miles on a bicycle. The stands are 10 miles or more. Tricycles and trailers don't change that issue much.