pedrail

from The Century Dictionary.

• noun A form of traction-engine, so constructed that the wheels rest their weight not on the ground-surface but on the units or links of a jointed chain, fed in front of the machine as it advances, and laid by it on the ground for the wheels to run on.

from the GNU version of the Collaborative International Dictionary of English.

• noun A device intended to replace the wheel of a self-propelled vehicle for use on rough roads and to approximate to the smoothness in running of a wheel on a metal track. The tread consists of a number of rubber shod feet which are connected by ball-and-socket joints to the ends of sliding spokes. Each spoke has attached to it a small roller which in its turn runs under a short pivoted rail controlled by a powerful set of springs. This arrangement permits the feet to accomodate themselves to obstacles even such as steps or stairs. The pedrail was invented by one B. J. Diplock of London, Eng.
• noun A vehicle, as a traction engine, having such pedrails.