The illusion of motion

I scared a taxi driver today. One of those fearless bandits of the byways lost it and used his hooter like a aspirant vuvuzela performer. I was minding my own business, putting on makeup and looking for my keys when there is this frantic hooting from behind. All because I was unconsciously rolling back, just a little bit. Usually one is so aware of any motion in a vehicle that we even
imagine it when none exists. The illusion of reverse motion is the
best word we have come up with to describe that sensation of brake
failure, when in a stationary vehicle, you feel like you are sliding
backwards. It's explained that you have as a reference point a moving
vehicle.  It's that traffic light creep speed that does our brains in,
too slow to be obvious we assume it's not moving. But I believe there
is a word out there,  one word to describe it. If you know please tell me.
In old western movies the wagon wheels seem to be going backwards, we
know they are not, but the eye is fooled by the spinning spokes. Like
when children spin around and around and make them selves dizzy, and
suddenly the earth is spinning. Well it's spinning all the time but
that is the only time we can see it.  If the earth is moving at 106
211km per hour, and we can't feel it until we make ourselves dizzy
then that explains the lapse of perception when our brains can't
conceive of exactly how fast we are going. That explains why in a
luxury vehicle without the reference points of straining engine, or
rough road surface we feel like we float in a world above the road,
and how quickly that speedometer moves up, imperceptibly, and before
we know it we are hitting 180Km and don't even feel it. After a trip
averaging 120Km it always feels like you are hitt8ngh an invisible
wall when you have to slow to 60. The motion follows you through your
day.
A motoring myth I would love a decisive answer on is whether
freewheeling will save fuel. Some say it does, and others say it's
inadvisable, dangerous and what is saved on fuel is spent on braking.
If you can prove it either way would love to know.