Stating that the means and methods of transporting freight over the highways are governed by six factors, the author enumerates them as being the number of ton-miles of goods to be shipped, the shipping points and destinations, the kinds of highway available, the types of vehicle most suitable, the cost of operation per ton-mile and the rates that should be charged for the service. The purpose of the paper is not to answer these questions but to determine whether present practice is headed in the right direction.
The conditions the highway must meet, in addition to the gross load of the vehicles, are the maximum tire load, the pressure per square inch exerted by the tire upon the pavement and the value of any impact blow upon the pavement. The impact blows of pneumatic tires are practically negligible, while solid tires build up the impact to many times the weight of the wheel load; this is proved by impact tests of tires which are described in some detail and illustrated.
The state of development of the pneumatic truck tire and average mileage obtained by its users are treated specifically, spring suspension and steering are discussed, a summary is presented in three divisions and an appendix, giving three specific results of tests made by the Bureau of Public Roads on the six-wheel truck the author describes, is included.