Why does 60 mph look much faster on a rollercoaster than in a car, but 70 mph in a greyhound bus looks like 50 mph?

It's called "a side effect of autism."

Forced perspective. You will see things differently in a changed environment.

Abrupt changes, close structure passing by, noise, all increase perception of speed on the roller coaster. When you're going 80 mph down an 8 lane freeway and nothing to see to the sides, it feels like crawling- especially when the police aircraft swoops by at 150 mph

Angle of the observable dangle matters.  The closer you are to the road surface the faster it seems.

  Try in a go-cart and 40mph is screaming fast.  Yet, if you are in a plane flying off the ground then you see more(as you have a bigger viewport)

A greyhound bus is high in the air compared to a car.

It's called, luxury. Roller coasters are open air rattle traps while modern buses are as smooth as a Cadillac.

I do not know the name of it, but  the closer you are to the action, the more you notice it.  In an airplane you are travelling several hundred mph, but you do not notice it because the ground  is so far away.  On the runway you are much slower, but you notice the speed.    If your greyhound bus had a glass floor and the side was all window, you would notice the speed more.  If the bus was wide open like the roller coaster, it would be just about as thrilling.  (The roller coaster has built in dips and loops that the bus does not)

its called G-force, the wind you feel when on a ride. a roller coaster has lots of g force due to there being no barrier between the wind and your face. in a car, a windshield blocks your face so you don't feel much.

Out in the open air with hands waving, nothing between you and death, twisting, turning, looping, in a tiny shell flying through the air, that is a roller coaster.

Coasting along on a smooth freeway, inside a small house on wheels weighing tons, that is a bus.

Hard to compare except the first is designed to scare the **** out of you, the second is designed to make you feel safe enough to do another trip.

riding  in  a  greyhound  is  cool … even  more  enjoyable  than  in  a  plane.

Mental retardation.