On a large scale the system is impossible, and the substitution of pack animals for porters is but little less uneconomical, except in mountainous countries and desert lands, and in the latter, it would seem that the reign of the camel is approaching its end, since in most places where a camel can go a car can follow.
TWO-DIMENSIONAL MOVEMENT
The above, I admit, is a very brief summary of an immense and complex subject, namely, the bridging of the gap which exists between the producer and the arterial railway, or the producer and his market, if it be a distant one. Ruling out pack and porter as being too uneconomical to be used on a large scale, we are left with the wagon, the lorry and the light railway. All these three means can cover great distances, but they do not solve the problem, because the solution does not only lie in power to traverse distance, but in ability to cover the largest area in the shortest time.
The difficulty so far has been that the wheel demands a road and destroys a road, and that, whilst it is easy, though frequently very costly, to make a road which will suit a wheel, it is most difficult to make a wheel which will not damage a road; for failing a cheap and simple form of Pedrail wheel, a system of multi-wheels has to be resorted to, and this system leads directly to the tracked machine, which not only can dispense with roads, but, what is equally important, can make its own track, just as the feet of a man form a path by frequently crossing the same piece of ground.
This is not the place to examine in detail the technicalities of roadless vehicles; but to-day there are two main types of these vehicles; an all-tracked machine of the tank type, and a half-tracked machine which has wheels in front and tracks in rear. The first is more suitable for heavy loads, and the second for light.
In the manufacture of these vehicles three main problems must be solved:
(1) The vehicle must be able to use roads without damaging them; nor must it damage the surface of the ground it travels over.
(2) It must be able to move across country without damaging itself.
(3) The cost per ton-mile must be equal or lower than that of existing vehicles.
It may seem a paradox to lay down that the first requirement of a roadless vehicle is that it can negotiate roads, but, in fact, it is not so; for it stands to reason that, when prepared tracks do exist, it is only wasting time and energy to travel across country. Further, if the tracks of the vehicle are so constructed that they do not damage roads, they will not damage the surface of the ground, and, consequently, by continually travelling over the same ground, they will compact and consolidate its surface and rapidly form a road of their own which will require no metalling. This advantage is one of the great secrets of its success.