"Free parking is not, of course, really free. [...] Everybody pays, whether or not they drive. [...] young people drive a little less than the middle-aged and the poor drive less than the rich. [...] Free parking represents a subsidy for older people that is paid disproportionately by the young and a subsidy for the wealthy that is paid by the poor."
http://www.economist.com/news/briefing/21720269-dont-let-people-park-free-how-create-traffic-jams-pollution-and-urban-sprawl?frsc=dg%7Ce