Real ? Not sure.
To quote the people who host this:
QUOTE
Is it theoretically possible to drive a car upside down in a tunnel? A F1 car produces 1:1 weight to downforce ratio at 80 mph. This means it can theoretically cling upside down at that speed, but without much traction. At about 120 mph the ratio becomes 2:1 which means the force on the wheels will be equal to weight of a stationary car and there will be enough traction (provided the fuel supply etc. is made to function upside down). The ideal environment to do that would be in a perfectly cylindrical tunnel. (We don't think that the tunnel in the Mercedes vidoe would do the trick. - Flixxy Editor ;-)
But - I love the sound this thing makes !!!
http://www.flixxy.com/mercedes-benz-sls-amg-tunnel.htm
Who's up for a drive ? Eisenhower tunnel isn't too far from here