We all imagined flying cars by the predicted years on iconic movies like Back To The Future or Blade Runner, yet nothing came. The designs I've seen are pretty lame compared to the awesome futuristic cars envisioned in these movies. Im not convinced at all we'll be seeing viable flying + road cars convertibles by 2020.
In theory flying cars should reduce the level and danger of 'road' accidents. It's unclear yet how they'll work but in theory you're not limited in terms of lanes etc as cars can simply fly above one another, there also won't be the danger of distractions from pedestrians, animals etc that you'd otherwise have on the road.