Though trains rarely overturn strictly
from centrifugal force from speed
(they usually derail first). This same
logic can be used to derive the overturning speed. Conventional wisdom dictates that
the rail vehicle is generally considered stable if the resultant of forces falls within the
middle third of the track. This equates to the middle 20 inches for standard gauge
track assuming that the wheel load upon the rail head is approximately 60-inches apart.
As this resultant force begins to fall outside the two rails, the vehicle will begin to tip
and eventually overturn. It should be noted that this overturning speed would vary
depending upon where the center of gravity of the vehicle is assumed to be.