Why aren't electromagnets used for vehicular travel? versus oil/gas?

Have you ever tried to put a north end of a magnet to a north end of a similar sized magnet?...they repel...and it is very hard to make them touch...especially larger magnets. So why not have magnets on the underside of a vehicle, and on the road surfaces? If electricity is needed, solar panels and small amounts of energy can be used to keep the charge on the roads magnetic surfaces...???