ROAD ENGINEERING.

Manawatu Herald, Volume L, Issue 3979, 3 August 1929, Page 3

ROAD ENGINEERING.

FROM PACK TRACKS TO BITUMEN. ADDRESS BY MR, H. V. BOND. Mr. H. V. Bond, Engineer to the Manaiwatu County Council, delivered an interesting address to the Foxton Lunch Club on Thursday on the subject of “Road Engineering.” Mr. H. E. Gaiibett was chairman and introduced .the speaker. Our roads to-day, said Mr. Bond in his opening remarks, are very much different from what they were a few years ago. Many of them, in the first place were merely paJck tracks. These pack tracks were followed by bullolck and horsedrawn vehicles and the wheel marks of these carts and drays were filled in and our roads ultimately defined. The settlers then set about metalling their roads, and- for the-pulrpose* small loans were raised and from two to three inches iof metal spread over the 'surface at a cost of fVom between £3OO and £SOO pea* mile. The settlers were fortunate then if £lO per mile per annum was spent on their roads in maintenance. Grade was the main consideration in ' those days and, with an absence of motor traffic, the roads lasted 'many years. The motor-ear first came to this country in 1903 but then it was tiie roads that gatve the motorist the greatest trouble and the roads did not suffer to any great extent as the motorist was not able to travel fast enough to do much damage. With better roads, however, and the production of better and more suitable cars and motor vehicles, the roads began to suffer, In 1923, twenty years after the introduction of the first motor-car into New Zealand, there were 100,000 motor vehicles in this country and local authorities financial burdens were increased to maintain l he roads in any tiling like decent order. Maintenance cost rose from £lO per mile to £6O and even higher and this presented a big problem to those concerned light throughout .tiro country. Some local bodies were fair seeing and erected toll gates and with the money derived therefrom laid down tar-seal-ed roads which saved them a great deal in maintenance. The need for tar-sealing the roads became apparent but the local bodies were helpless to do anything without imposing unfair taxation on the ratepayers. In 1923 the first steps were tak.cn by the Government to assist the local bodies in the matter and in 1924 the Main Highways Board was set up. By this time the motor traffic on our roads had almost doubled. In five years it had risen from 100,000 to 190,000 vehicles, so it was easy to realise what the roads had to put up with. It was found to be practically impossible to maintain metal roads with so much traffic on it, The cost rose to somewhere in the vicinity of £l4O per mile. With this increase in traffic, though, came a stabilising of maintenance charges, which for many years, had been soaring to an alarming extent. This was due to the fact that the various local bodies were undertaking tar-sealing work on their highways which had a tendency to cut maintenance costs out for some years. Maintenance costs in this country, with* the paving work going on so rapidly, has reached its highest point and will now commence to decline. It would not have been economical to 'keep on maintaining metalled roads under the existing circumstances, said Mr. Bond. Although £l4O ums mentioned as the cost of maintenance per mile this was local and the general average Ifor the Dominion at the time of the formation of the Main High-

ways Board was somewhere in the vicinity of £3OO per mile. 'lt would be easily seen that this sum would go a long way towards paying interest and sinking fund on a loan to pave the roads. Reconstruetional work was a big undertaking, however. The construction of permanent highways was found to be between £4500 and £7OOO per mile but Mr. Bond had read of one ease where 143 miles of highway had cost £424,000 to carry 200 vehicles a day. That certainly was not road economics. The road had been of concrete foundation with a hot mix bitumenus top. In France there was also 2000 miles of road which cost iSO million pounds to put down, or £25,000 per mile. These roads were e(Mainly on the expensive side and the ratepayers would have to pay for them. Nothing like that was contemplated in New Zealand said the speaker. As long as there was a. good solid metal foundation a hot mix bitumen surface could be put down which would last for many years. This, of course, did not apply to 'the cities where the traffile was more congested and much more, restricted. Extra .work was necessary there. A concrete base with three inches of hot mix bitumen was the best treatment for such roads. Concrete alone was not found to be satisfactory. It was quite all right for some time and presented a good running surface, but once the surface broke, which it was liable to do, the road would wear very quickly. If a local body invested its money on a concrete road then it was necessary to protect that money by sealing the top of the road with a carpet of some bitumenus mixture. Although fhetre had been a good deal of experimenting in connection with concrete roads, so far it had keen impossible to find a painting of anything that would adhere to the concrete. Such mixtures flaked off and the partly uncovered road was found to go rapidly into holes. Many of the local bodies with miles of concrete road under their care to-day find that they are up against it to keep a wearing surfalce on their roads.

Referring to the amount of traffic roads are expected to carry, Mr. Bond said that he had read recently in a Reading Journal that in Los Angeles there was a boulevard over which 72,000 motor vehicles passed an hour. It was constructed of six inches of concrete on top of which was three inches of asphalt. A New Zealand tally would show something like 300 vehicles a day on many of the country roads. In New Zealand the cost of constructing paved roads was between £SOOO and £7OOO per mile and in concrete between £BOOO and £9OOO.

The hardest problem the local bodies were faced with to-day was to maintain their existing old metalled roads. The motor traffic swept the metal off and the boulders in the foundation made their appearance. The road grader was then sent along and dragged these boulders out and it. was very often the boulders that the motorist hit and which made him complain of the bad state of the roads. The old horse grader had now given place to the motor grader. 'Some people considered that the motor grader was of no use and that it skimmed over the road 'but Mr. Bond said that if it wasn't for the motor grad dr it would be practically impossible to travel in a car between Foxton and Palmerston North. The Foxton-Sanson road was graded every fortnight and two hours after it was hard to tell that the grader had been over the road. Metalled roads soon ran up maintenance cost and if a local body did not pave it would be hit very lyA lot of things have to be considered in putting down a road nowadays which were never given thought a. few years ago. Alignment was the chief thing to-day, and little thought of in the past. Grade was the chief worry of those days when horsedrawn vehicles were called upon to haul their loads through the country hut a good paved road over a hill does not trouble a motor vehicle to-day. A great deal of time was being spent on straightening the roads though. It had been laid down that no curve is to be of less than a five chain radius and this was the reason why so much time was being spent on bends and curves between Foxton and Palmerston North. In conclusion Mr. Bond said that it was not difficult to lay down good roads to-day, but if the people wanted good roads then they would have to pay for them and good roads meant a good deal of expense. They were,' however, a. saving in the long! run. At the conclusion of his address, Mr. Bond was accorded a hearty vote of thanks on the motion of Messrs IF. rCJ. Raikes and W. H. Walton.