Previous Answer => "Because of the law of inertia."
Improved Answer => Well, yes I suppose, but it is not necessary based on that fact.
Since Roller Coasters have a special three-wheel design that keeps coaster trains on the track NO MATTER WHAT, banking doesn't "keep the ride on the tracks". If anything, banking keeps the coaster safe (in terms of G's) and comfortable to actually be enjoyed versus being painful. A coaster and it's riders will follow the track no matter what, since again of the three-wheel design patented by John Miller in the 1920's AND the restraints on rides that keep people in. It is the G's that concern designers, not if the train will fall off.
wood
the tracks
yes; wherever the coaster touches the tracks there is static friction pressing against it and it pressing against the tracks, thus keeping it from flying off.
the tracks
Yes, in the tracks and the wheels the roller coaster cart rests on.
See the straight coaster picture and curve ones? Click on them to build a piece. Its the same as the turn tracks and straights.
The wheels are on top, between and below the tracks.
If its moving it has kinetic energy
banked turns
There is a few principals that are looked at when building a roller coaster. Some principals that are looked at are what keep coaster cars flying around on their tracks, the tolls that keeps everything running and the forces that make the ride fun.
you have to get 5 stars on all of the tracks and then there is an arrow to the right of your screen....
Its very simple, first make to stations, its impossible to make two coasters, make your coaster so that the end it crosses over to switch tracks.