Present military concepts call for highly mobile units capable of rapid dispersal and efficient movement across country where no roads exist, and many current civilian engineering tasks require movement of men and materials long distances over roadless terrain. Oversnow transport is a particular aspect of the general problem of cross-country mobility, but the characteristics of snow-covered regions are such that special techniques and equipment are required for efficient operation. In order to fully understand the action of vehicles in snow and to formulate sound design criteria, it is necessary to develop a theory which permits quantitative analysis of trafficability problems. For practical purposes, vehicle evaluation is at present made from the results of relatively simple field tests which give drawbar pull as their main indicator. The best practical evaluations are made by observing the operational capabilities of vehicles in various types of snow.