How Did the Road Come Into Existence: The Experimental or the Scientific Method: The Haphazard Road: The Case for Design in Road Construction.
In order to understand any matter, especially if we have to understand it for a practical end, we must begin by the theory of the thing: we must begin by thinking out why and how it has come into existence, what its function is, and how best it can fulfil that function. Next we must note its effect, once it is formed, and the results of the fulfilment of its function.
What then, to begin with, is the origin of the Road? Why did this human institution come into existence, and how does it tend to develop? How may it best be designed to fulfil its function?
When we have decided that we can go on to the next point, which is: how does the Road, once formed, react upon its environment; what physical and (much more important) political results flow from its existence?
The answer to the first question, “How did that human institution, the Road, come into existence, and why?” is simple, and will be given in much the same terms by anyone to whom it is addressed. The Road is an instrument to facilitate the movement of man between two points upon the earth’s surface.
If the surface of the earth were uniform in quality and in gradient—that is, if it were of the same stuff everywhere, of the same degree of moisture everywhere, and everywhere level—the Road between any two points would clearly be a straight line (to be accurate, the arc of a great circle) joining those two points. For when we say that the Road exists “in order to facilitate” travel over the surface of the earth from one point to another the word “facilitate” includes, of course, rapidity in progression, and the straight line is the shortest line between any two points.
But the surface of the earth is highly diversified in quality as in gradient. Therefore the trajectory or course of the Road is not in practice, and should not be in theory, a straight line from point to point. That straight line has to be modified if we are to give to the Road an ultimate form such that it shall best serve its end; and when we come to look into the problem we shall see that it is one of very great complexity indeed. That is where the study of the theory even in its most elementary form becomes of such value to the execution in practice. We discover by studying the theory of the Road how many and how varied are the elements of the formula we have to establish. We become prepared in that study for the discovery, in each new particular problem, of any number of novel modifications not present in problems previously attacked.
So true is this that the whole history of progress in road-making is a history of discovering methods for dealing with obstacles either novel in character or only appreciated after lengthy use. Let us begin at the beginning, with the very elements of the affair.
The first element in the theory of the Road may be put thus: To find a formula of minimum expense in energy for communication between two given geographical points under given conditions of travel and carriage.
The diversity of geographical circumstance moulds the formula into its final shape through balanced modifications of the direct line.
The most obvious modifications to a direct trajectory arise from the two primary circumstances of surface and gradient. It is easier to go over one kind of soil than another; easier to go over one kind of surface in summer and another in winter; easier to go over one kind of surface in wet, and another in dry weather; easier to go over one kind of surface with a heavy load and another with a light load; over one with sumpter animals, over another on wheels, and so on.
Again, it is for all kinds of travel easier to go upon the flat than uphill, and this element of gradient is much more complicated than at first it would appear. Thus travel of one kind—travel on foot, for instance—can take a sharp gradient for the sake of a short trajectory more easily than can traffic with burdens; and traffic with burdens carried by animals can take a sharper gradient with advantage than can wheeled traffic; and wheeled traffic differs according to the character of the vehicle in this respect.
Again, a road of diverse use must strike a compromise in its formula between the various needs subserved. If the great bulk of its use is to provide for rapid military advance by marches, you must sacrifice to shortness some of the easier gradients which would be demanded for traffic mainly civilian, yet if of three main users even the least important is incapable of more than a given gradient, your formula can never exceed that gradient, and so forth. So we have even in this simplest and most primary of all analyses of the Road considerable elements of complexity appearing.
As the study progresses an indefinite series of further complexities arises, and one soon reaches that crux in the theory of the Road which has led to so much discussion and which some still call unsolved: whether the formula of the Road is best left to the unconscious or half-conscious action of experiment, which in time should lead to an exact minimum of expense in energy, or whether it is best to arrive at it by a fully conscious, exact, and (as we say to-day) “scientific” examination of all the conditions and a deliberate and immediate conclusion upon them.
Should the road grow or should it be planned? The discussion is not idle. The clash of opinion upon it is at the root of the contrast between national systems, and a right answer will make all the difference between success and failure in our approach to a new road system such as is now upon us.
I maintain that of the two theories the second is just: that a gradual experimental growth in its roads, a method coincident with local caprice, burdens with imperfect communication the society adopting it; that conscious design is essential to efficiency. And this I propose to illustrate by a single example. Take two points A and B, such that a line joining them must lead across a marsh, a river, and a range of hills. Let some primitive wanderer make his way from A to B, knowing, when he is at A, the direction of B by, let us say, a distant peak overtopping the range between. That primitive wanderer would first of all skirt about the marsh and, finding its narrowest place at C, would set to work and make his causeway there. Having crossed it, he would come to the river. He must either swim or ford it. Supposing him to prefer, through the necessity of a pack or what not, to ford it, he casts about for a ford. He finds one at D, and perhaps he also, if he takes time to look about him, finds another deeper one at E and another at F, but as his causeway is near D he takes that ford.
Sketch I.
Then he has to make for the hills. We will suppose that the peak directing him from beyond B is still visible. He takes his new direction from it and looks towards the base of the hills at G. There, in the direct line to the peak, the contours are so steep that the trouble of getting up would more than counterbalance the shortness of the cut. He casts about for a better chance, and at last finds a gradient just worth his while at H. He climbs up that; but though the gradient is easy on the A side at H on the far side it is very difficult, so he turns along the ridge to K, where he finds an easier down gradient: a spur leads him on by its gentle slope, and from the bottom of the spur he makes straight for B, which is now right in front of him and plain sailing.
Now, look at that track as established by our primitive wanderer and see how lengthy and inconvenient it is, how ill fulfilling the object of the traveller compared with what would have been established by even a moderately intelligent and cursory survey of the ground as a whole and the making of a plan. To begin with, it would have paid our traveller to take a little more trouble in crossing the rather wider gap in the marsh at L and the rather deeper ford at F, because he would have gained very much in time and space with comparatively slight extra effort had he surveyed the whole ground and thought things out. He was only led on to the ford at D because it was suggested by the crossing of the marsh at C. The first opportunity made the second. But to continue the plan: F is nearly opposite the easier up gradients of the hills, but, having surveyed that bad steep on the far side, he slightly modifies his road, crossing the ridge at M behind a summit which hid this way from the first traveller. Then he goes down the practicable, though steep, slope at N, and so reaches B. The first road produced haphazard by successive chances gives the lengthy and roundabout trajectory A—C, D, H, K—B. The second, with very little extra labour, gives him the far shorter and better trajectory A—L, F, M, N—B.
We see from this elementary example how the thinking out of the theory of the Road is of advantage in practice. It may be urged that the discovery of advantages as time goes on gradually improves the Road, and in this way half-conscious development will always give you the best road in the long run without studying its theory. But history is against that view. Europe is full of roads thus established haphazard, confirming themselves by use and by expenditure, and for centuries neglecting opportunities which would have been present to the eye of the most cursory and moderately intelligent survey.
This conflict of principle between growth and design in the creation of the Road is at the root of half our modern crises in road-making. The real issue is between those who would gradually add to or develop from custom and those who would radically impose new plans, and on a right decision the economic future of this country may well depend.
When we come to consider even the first of succeeding modifications we see still more clearly the complexity of any road-formulæ and the corresponding advantage of plan over habit. The marsh, the river, and the hill are but the beginning of the affair. There is a modification due to the fact that the marsh may not be permanent, nor the depth of the river; that the Road may be of special use at moments when the river is shallow or flooded, when the marsh is dry or, exceptionally, impassable. There is the modification of surface. Clay, for instance, is fairly good going in dry weather, but the worst in wet. There is the modification due to vegetation: the balancing of the effort involved in going round a dense scrub against that of cutting through it and of maintaining the cutting when it is established. There is the modification introduced by the instruments and science available for construction and for cutting. In one stage of development it will pay to take a road by a bridge across a deep river where in earlier stages of development it would have been necessary to seek a ford. In one stage of development it would pay to make a cutting through a scar too steep to climb where, in a lower civilization, it would have paid to go round it. The whole formula increases in complexity the more we examine it. It is a formula for the discovery of a minimum of effort. But in the establishment of that minimum you have to consider not only a very great number of factors, but the respective value of each to the whole, and your success in establishing the Road depends upon the accuracy of your judgment both as to the presence and as to the comparative value of all those factors.