Before a surveyor can decide upon the best material with which the streets of his town shall be paved, it will be well to consider the question of the class of traffic they will have to bear.

It must be remembered that three distinct interests have to be considered in dealing with this question, viz. (1.) The rate-payers, upon whom the cost of construction and maintenance of streets falls. (2.) The owners and employers of horses and vehicles who principally use the streets; and (3.) The inhabitants of the adjoining premises, who would be annoyed if the material selected were unduly noisy or dirty. In addition to these considerations, much depends upon local circumstances; the class of trade upon which the welfare of a town is dependent must not be lost sight of. A pavement suitable for a busy, pushing manufacturing city may not be suitable for a quiet agricultural or cathedral town, or for a town which is used as a health resort. Again, the question of the most adaptable materials must be considered, and the climate and physical character of a town should enter largely also into this question.

To condense the requirements of a good roadway into as small a compass as possible, the following may be given as some of its principal requisites:—

(1.) It must not be extravagantly costly in its first construction.

(2.) It must be durable and require the least possible amount of repairs at the least cost.

(3.) It must be safe, firm and hard, with an even face and yet giving sufficient foothold to horses.

(4.) It must be as noiseless as possible.

(5.) It must be so constructed as to be quickly laid down and repaired when broken up for water, gas, drains, or other purposes.

(6.) It must be of strong foundation, so as to carry the heaviest weight without subsidence.

(7.) It must be of such a shape as will throw off all surface water at once.

(8.) It must be of such materials as will make a minimum of dust or mud.

(9.) It must be easily cleansed.

(10.) It must be non-absorbent of impurities or moisture of any kind.

(11.) It must give easy traction upon its surface.

(12.) It must not cause jolting to the traffic.

(13.) It must not injure horses’ legs or hoofs.

Of the above requirements No. 1 affects the ratepayers alone; Nos. 3, 11, 12, 13, affect the traffic only, except that the occupiers of shops are indirectly affected by them; No. 4 affects both traffic and occupiers, and No. 10 affects the occupiers principally. The remainder of the requirements affect all three interests.

With reference to the wearing effect of traffic upon the surface of the roadway, no standard has yet been arrived at by which this can be determined with accuracy. In France a great number of observations and experiments have been made from time to time by the engineers of the Ponts et ChaussÉes, but their practice has been to count the number of “collars” passing a given section of a roadway in a given time, irrespective of the weights, speeds, or number of wheels such collars may be drawing. Mr. Deacon, the former Borough Engineer of Liverpool, has, however, reduced traffic to a standard of tons per yard width of roadway per annum. This he effected by having the traffic in any street carefully watched for a certain definite time, the number of vehicles, their character and approximate weight being noted as well as the number of horses by which they were drawn, and their number of wheels.

The effect of the traffic thus tabulated, arranged, and reduced to ton yards per annum, can be ascertained upon any roadway, and Mr. Deacon has given the results of his observations in a valuable paper on the subject of street carriage pavements which he read before the Institution of Civil Engineers.[7]

Sir John MacNeill has estimated that 80 per cent. of the total wear of a road is due to traffic, the remaining 20 per cent. being due to atmospheric causes. Of this 80 per cent. 60 per cent. he considers is due to the action of horses’ hoofs where the traffic is fast, and 44·5 per cent. where the traffic is slow. General Morin estimates the wear of a road due to horses’ feet to be two-thirds of all causes. There can be no doubt that the action of horses’ feet, shod as they are with heavy iron shoes with long toe pieces and heels, must have a destructive effect upon the surface of a carriage-way, and this may be easily observed when watching the ruts formed by any continuous line of traffic in a roadway.

The following remarks from a report of the Society of Arts on this subject may here be of interest. “It may be mentioned that as respects the horses’ shoes, attention has long been called to its defects by Sir Francis Head and others, but Sir Joseph Whitworth now points out the achievement of a decided and important improvement, which will have a large effect in road conservancy, as well as the reduction of noise. The improvement consists in the fastening of a rim of hardened steel, of about half-an-inch square, to the horses’ feet, and letting the frog grow to its natural size. One effect is to reduce by five-sixths the weight of the old shoe, or in other words to reduce by five-sixths the weight of the iron hammers constituted by the common horses’ shoes, pounding the road surface, and creating road dust and dirt, and distributing it about. The saving in this respect, as well as the reduction of noise by the reduction of the weight of rim, and also the saving of road wear, would warrant the imposition of the stimulus of a tax, or a toll upon heavy horses’ shoes to hasten this removal.”[8]

Up to the present date, however (1883), no general change has been effected in the manner of shoeing horses, notwithstanding these admirable remarks of Sir Joseph Whitworth upon the subject.

With reference to the question of traction upon roads General Morin, in his ‘ExpÉriences sur le Tirage des Voitures,’ states that the resistance to the rolling of vehicles upon solid metalled roads and pavements is proportional to the weight and inversely proportional to the diameter of the wheels. On solid roads he states that the resistance is nearly independent of the width of the tires when they exceed 3 or 4 inches, but on a compressible face it decreases in proportion to the width of the tire; the resistance further increases with the velocity on hard roads, but does not do so when they are soft.

The following table is almost universally now adopted as showing the traction upon level roads formed of different materials, asphalte being taken as the standard of excellence in this respect.

There are four forces constantly at work tending to destroy the momentum of vehicles passing along a roadway: they are gravity, collision, friction, and the resistance of the air.

The first of these is lessened by easy gradients in a road, the second can be overcome to a great extent by evenness of surface, the third by hardness, and the fourth, as well as all the others, by giving sufficient foothold to the animal drawing the vehicle.

Another excellent table[9] prepared from experiments made by Mr. Amos on different descriptions of pavement in the City of London may be useful, and is here given:—

The following table from Law’s ‘Rudimentary Treatise on Civil Engineering’ shows the force required to move a load of a ton weight on different descriptions of roadway, the limiting angle of resistance, and the greatest inclination which should be given to the road being also stated.

As a matter of fact, however, the gradient of a macadamised road should not, if possible, exceed 1 in 20,[10] experience having shown that a horse, unless the hill is a very long one, is able to draw his ordinary load for a level up such an inclination, whereas, if it is steeper he is sometimes stopped altogether, even though the carter tries the zigzag route so as to obtain an artificial ease of gradient.

The table given in ‘Molesworth’ upon the same subject is too well known to be repeated, and another table may be found in Sir Henry Parnell’s work on roads, which gives a comparison between the draught necessary on a well-paved road at 2, on a well-made, clean macadamised road at 5, whereas on a wet and muddy gravel or flint road it rises to 32!

Mr. T. D. Hope, of Liverpool, assuming the power of traction at 100, gives the following table:—

And Lieut. Crompton has given the resistance of wheels in lbs. per ton on different surfaces as follows:—

Here “newly-laid metal” comes out very badly, and points to the necessity of rolling, of which I shall speak in a future chapter.

Whilst on the question of wheel resistance, it may be well to note that the small front wheels of a waggon cause considerably more harm to a macadamised road than the larger hind wheels. In the smaller diameter any loose stone or obstruction is pushed along in front for a considerable distance, often tearing up the surface of the road, whereas in the other case the stone is forced into its place or crushed as under a roller.

On the question of “safety” to traffic, Mr. Haywood, the eminent Surveyor of the City of London, has caused several most complete observations to be made from time to time, the results of such observations being detailed by him in various reports. Amongst other useful information compiled by him, he has ascertained that a horse will travel 446 miles upon a roadway paved with blocks of wood without a fall, 191 miles upon asphalte, and 132 miles upon granite setts. I cannot do better than give verbatim his remarks upon this point:—

“Slight rain makes both asphalte and wood more slippery than they are at other times. On asphalte the slipperiness begins almost immediately the rain commences, wood requires more rain before its worst condition ensues. The slipperiness lasts longer upon wood, on account of its absorbent nature, than it does upon the asphalte; when dry weather comes after the rain, when asphalte is in its most slippery state, and the horses fall on it very suddenly, on wood their efforts to save themselves are more effectual; wood also is frequently in that peculiar condition of surface in which horses slip or glide along it without falling. A small quantity of dirt upon asphalte makes it very slippery, wood requires a large quantity. Slipperiness can be temporarily cured on both pavements; on the asphalte by sprinkling it with sand, on the wood by sprinkling it with gravel. The result in both cases is dirt. The sand thrown on asphalte helps to wear it out, the gravel thrown on wood tends to preserve it. When a horse falls on asphalte it has difficulty in getting up; on wood it rises more readily.”[11]

In streets crowded with traffic, the constant stopping and starting, especially on any surface that is slippery, is very trying to horses. Attention has lately been directed to this point with a view to the storage of some power in a vehicle, either by the compression of a spring in stopping or by some other mechanical means, in order that in starting the driver may at will liberate this power so as to assist the horse in overcoming the inertia of his load. These trials, however, have not at present met with much success.

Before closing this chapter on traffic, it will be well to point out that nearly all vehicles travelling rapidly can pass each other safely if allowed a clear space of eight feet; hence all roadways should, if possible, be made of a width between the kerbs of some multiple of eight: a convenient width for the footpaths, so far as foot-passenger traffic is concerned, is found to be one-fifth of the entire width of street. It is scarcely necessary to add that vehicles pass each other on the left side, pedestrians on the right. It is not easy to assign a cause for the former beyond custom, except that the whip is held in the right hand, and in consequence free play is given for its use as the driver sits on that side and can watch his wheels in passing. In France and other countries the right side is the “rule of the road.” In the case of pedestrians it is perhaps more convenient for many reasons to pass on the right side, one being that the umbrella or parasol is always carried in the right hand, which is also used to remove the hat when bowing, and another because one’s tendency in passing any obstacle is to give way with the left shoulder. For regulating the traffic and for the protection of foot passengers, “sanctuaries,” as they are termed, have often to be constructed by surveyors in broad streets or awkward centres of traffic, and it is well to place a lamp-post on these sanctuaries, on which may be advantageously fixed a notice, “Keep to the Left,” so as to regulate vehicular traffic. On the lamp-posts at the edge of the footpaths it is also sometimes customary to fix small enamelled iron plates bearing the inscription on both sides, “Keep to the Right,” so as to regulate the pedestrian traffic.

Of the danger to life and limb to pedestrians in London much has frequently been said, and no wonder, when we consider the number of persons who are daily injured and sometimes killed according to the Registrar-General’s returns. Some years ago it was proposed to erect light iron bridges over the most dangerous crossings approached by winding stairs, but “time is money” in the mighty metropolis, and the scheme was abandoned because it was felt that most persons would prefer the risk of being run over rather than spend the time in ascending and descending the necessary steps for this purpose.