Seth Riney is saving the planet one car journey at a time. As founder of PlanetTran, the livery service that uses only hybrid cars, Mr Riney operates a fleet of about 40 Toyota Priuses in Boston and San Francisco that boast an average fuel economy of 47 miles per gallon.

Mr Riney, pictured below, a former systems engineer, is a self-described “practical environmentalist”. He knows the greenest way to get from place to place is to walk or cycle or take public transport. “But since there is a practical need for individuals and small groups to be moved around,” he says, “you might as well do it as efficiently as possible.”