The Commercial Use of Highways.*
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By H. Howard Humphreys, A.M.Inst.C.E., ivi.I.Mech.E.
Views of Road Makers.
Mr. GLADWELL said the question of foundation, to which some speakers had referred, was largely a question of degree, and what might prove to be a good foundation for one district or one county would be unsatisfactory in another. Clay was not a satisfactory foundation for roads, and, in all cases of road construction they had first of all to consider the character of the foundation. Where one had a foundation of natural gravel or rock or of hard boulder clay which, in dry weather could be safely coated with a waterproof material, then in that case one would have a good foundation. lie would go further and say with a waterproofing system one could make a strong road of a weak one if the foundation was not too liable to be influenced by moisture. he had been over roads in Nottinghamshire which were very good roads in dry weather, but very bad roads in wet weather, so it was obvious that it was difficult to lay down hard and fast rules with regard to what constituted a good road. It was obviously impossible for the road engineer to cater for every kind of traffic, and he therefore had, to the best of his ability, to strike a happy medium. In his case, he found it impossible to advise his authority to double its expenditure even for a road which would have three times the life of the existing road. That being the case, he had to find some method of road making not greatly in excess ot the existing method in regard to cast, but giving better results. He had been led to the experiments that had been carried out in his own district, and he really hoped to see some results from the demonstration given that good roads could be produced without spending large sums of money. No doubt the modern tendency in regard to expenditure was to expect the State to pay for it, but he had yet to learn that the money which the State got hold of dropped down from heaven, and, if the ratepayer did not pay that directly, he paid it indirectly.
Mr. DOUGLAS IviacrcRNari: said he would deal with two points only arising out of his own experience. In regard to what had been said as to the damage done by small wheels, he had carried out some experiments in this direction, and although it had only been possible to increase the diameter, in the case to which he referred, from 40 to 42 inches diameter, he had found that even that slight increase caused the wheels to do less injury to the road, and at the same time reduced the tire cost 4th of a penny per car mile. Although he was unable to give actual figures, he also felt certain that the use of these larger wheels had a satisfactory influence on the maintenance charges. His second point related to dustless roads. The idea of the National Dustless Roads Committee was to carry out tests with
various materials tending to minimise that dust evil. But then came the work of Mr. Gladwell, and he was bound to say that there was nothing to compete with his system, and that under the circumstances there appeared to be no need to go on with the programme which the National Dustless Roads Committee had laid itself out to follow.
Mr. Cwaizt.Es directed attention to one or two legal aspects of the case. With regard to tar, he pointed out that trouble had arisen in Hampshire in consequence of dead trout being taken out of the River Itchen, and he thought that was a point which called for the careful consideration of road engineers with a view to adopting some other method in the case of roads running near streams and likely to be polluted from the road coating material.
Major Pain_ said that, with respect to military operations, it was necessary not only that the main roads, but that the by-roads should he put into a condition to take military traffic. 'He had found that on Chatham Hill, which had a grade of one in ten, it was impossible to work road engines with safety, and, in the case of Swale Bridge, giving access to the Isle of Sheppey, referred to by the author, the only method of getting some heavy guns on to the island was to put them on the rail and get them across the railway instead of the road bridge.
Some Details of Cost.
Mr. MANNING referred to the question of cost. He said that starting with Mr. Gladwell' s experience he was able to produce a road which had proved very satisfactory. That road cost Is. Oct. against is. 6/-d. for the road it displaced. In 1903, he laid a long section of tarmac as an attempt to get a waterproof road. He would point out that, in his district, the roads had practically grown up without having any foundation. It was practically impossible for him to reinforce the whole ot his roads, but he had strengthened the abutments, so that the crown to a great extent carried itself, and had then coated with tarmac. In that case the cost was 2s. 3d. per yard laid. That was done in 1903, and he had since spent only 3d. per yard in maintenance, and the road was absolutely good. The toad alongside done in the ordinary way had cost is. 54d. per yard, had 'been repaired in 1905 at 9d, per yard, and since then at Sd. per yard. The faults of tarmac were slipperiness in wet weather and higher first cost. He had extended Mr. Gladwell's system to another mile of road, and the cost of that had been Is. 7-.W. per yard. His experiments proved that the application of tar to the surface of the road was by no means likely to give results of a lasting nature, and unpleasant emanations came off the surface. The tar used in Mr. Gladwell's system was specially-distilled, refined tar, from which the whole of the poisonous constituents had been taken out.
Mr. HUMPHREYS, replying on the discussion, said he had had a good deal of experience of road making, but the experiments conducted by Mr. Gladwell offered a very hopeful prospect. With regard to the financial question, it was agreed that, if roads were given a good foundation, that would save money in, the long run. With regard to State aid, they were undoubtedly looking for an Imperial grant, and indeed were within measurable distance of obtaining it. It was true that money obtained from the Imperial Exchequer was paid by ratepayers, but such a grant would have the effect of equalising the burden, as it was unfair to put upon local authorities the cost of improving and maintaining the roads in and about London and in large industrial centres. It was necessary that some help should be given in these cases, With regard to Major Paul's question as to an engine being unable to be safely used on Chatham Hill, a gradient of about one in 15 was about the accepted limit for the work of such an engine. He was glad that attention had
been directed in the discussion to the size of wheels ; this was a very important point. Undoubtedly if the diameter of the wheel is increased the strain on the road is decreased, and he was glad that the matter was receiving the attention of those responsible for the construction of motor vehicles.
On the motion of Mr. \Teach Wilson a cordial vote of thanks was accorded to Mr. Humphreys for his paper.
Mr. Douglas Mackenzie moved a vote of thanks to the Chairman and this was carried unanimously.