Green Lantern: First Flight
Most coasters have wheels above, below, and to the inside or the outside of the rails.  Because Green Lantern cars don't turn to the left or the right, slightly flanged wheels above and below the track and very small wheels outside of the rails are used.  These side-wheels are so small that they are nearly hidden by the green wheel-mount assembly.

Typically, the "drive wheels" above the track are larger than the "up-stop wheels" underneath the track, but because these cars spend half of their time sitting above the track and half the time hanging under the track, the two sets of wheels on opposite sides of the tubular steel rails are the same.

©2017 Joel A. Rogers.