Only when it hits the curve.
Only by a small amount.
And think about what you are saying.
When you are at rest your butt is putting your weight x 1g on the seat.
When you are on the curve you are putting your weight X 4.5g on the seat.
When you are on the the vertical you are putting almost no weight on the seat because you are floating out of it.
So therefore it follows.
-When the car is in the station its 10 tonnes on the track (or whatever)
-When it is on the curve to vertical it is putting 45 tonnes on the track.
-When it is coasting vertically, its putting almost nothing on the track.
A really good example of the physics of this in action is on an impulse coaster.
Notice how the curve to vertical has quite heavy tube supports and a cluster of track connectors.
This is the highest g load section of the ride, as it swoops under the trains are really pulling down on the track.
But when it gets to the vertical part, there are minimal extra supports. Why?
Because at this point the train is coasting up / falling parallel to the direction of the rails/
its not pushing down on the track, its "rolling with it", so the track is practically self supporting.
And then in the station its lightweight supports again because even though its going at high speed, its still only pulling down 1g
Another example would be on dive coasters. The track ties are further apart on the vertical part because the load is minimal, and then get close together again on curve at the bottom when the Gs hit.
Compare the distance between supports normally versus on the vertical part:
But yeah Slick is right, there would be a little bit of force on the car, eg wind blowing it sideways that would try to 'twist' the track, the car being unbalanced and wanting to shear a bit, but not a whole lot.