According to Dean, “Unless we come up with alternative fuel sources and rethink our reliance on a hyperinflated consumer based economy, we may be left with no other options than to hook our cars up to a horse. As a symbol of this I [will] take either a Cadillac Escalade or HUMMER H2, which have become monuments to America’s consumption, greed and arrogance, and convert it to a horse cart. The cart will maintain all its former glitz and glamour: chrome rims, GPS, working sound system, DVD player, and TV screens. But [it] will be pulled by a horse.”
Source: backtothefuturama