The streets I see are filled with big chunks of metal moving past, spewing gasses. That is how it appears to me, now, over a year since I sold my car. Sure, these chunks also include plastic, sometimes leather, probably rare earth metals for the electronics, and some stone for the glass. It is the metal, though, that contributes most to their mass, and that makes them seem disproportionately big and heavy when they are moving a 170 pound person up and down the road. According to Slate, the chunks weigh about 4,000 pounds, on average, with or without the driver.