A bit about the file format used:

The first 144 bytes are the control-points and tangent-points
for the track curve. There are 24 points in all; 12 control-points
and 12 tangent-points. The points are stored in this order
CP1, TP1, CP2, TP2, etc (where CP=control-point and TP =
tangent-point). A Bézier curve segment is created using four
points, 2 cp's and 2 tp's. In the rollercoaster demo the second
tangent-point is always calculated by mirroring a tangent-point 
around the previous control-point to ensure that the movement is
smooth (equal direction & magnitude of the tangent vector at the 
curve-joins). See roller.c for an example of how this is done.

Next is NUM_STEPS * 4 * 4 short words, which equals
NUM_STEPS * 4 SVECTOR structs. Each step contains 4 SVECTORs,
top1, top2, bottom1, bottom2 (in that order). Obviously, the
top1 & top2 values represent the top of the track, and bottom1 &
bottom2 represent the bottom. :)