What exactly was that thing driving down the road?
Yes, an Ariel Atom.
Is that a car?
More particularly, the car is an Ariel Atom built in 2006 by a company called Brammo Motorsports. Brammo since moved on to make electric motorcyles. Current Ariel Atoms are made in Virginia by TMI Autotech.
The Atom is frighteningly fast and the supercharger whine is spectacular. As fun as the car is on the street, it really can't be fully understood until you get it on the track.