The road appears to slope downward, and drivers assume that the slope will accelerate the vehicle. Yet if they slow down, they are likely to grind to a complete halt. Despite every appearance to the contrary, the road runs uphill, not downhill. Unable to believe what has happened, many motorists stop-only to find that their cars begin to slide backward, a “uphill.”
Consequently, it's a popular spot for tourists in the area. But mathematician Philip Gibbs says that there's no paranormal or magnetic phenomenon at work. It's just an optical illusion:
There are several things that enable us to sense which way is up. The balance mechanism in our inner ears is one system we have, but visual clues are also important and can be overriding. If the horizon cannot be seen or is not level, then we may be fooled by objects that we expect to be vertical but that really are not. False perspective might also play a role. If a line of trees get larger or smaller with distance away, our sense of perspective is thrown off. Objects far away may seem smaller or larger than they really are.
People often overestimate the angle of a slope. If you are standing on a slope of 1 degrees it will seem like a slope of 5 degrees and if you stand on a slope of 5 degrees it may seem like you are on a slope of 30 degrees. Because of this effect the anti-gravity illusion can seem stronger than it should be even when you know the cause
Paranormal explanation and scientific explanation via The Presurfer | Photo: Ayrshire government