TARRED ROADS.

Northland Age, Volume 16, Issue 16, 9 January 1919, Page 6

TARRED ROADS.

The “Good Roads Committee” of the North Auckland Development Board have received the following opinions from prominent Civil Engineers re tarred roads. These were placed before the Mangonui County Council at its last meeting by Cr. Long, who said that they were exceedingly interesting and instructive. Mr. J. A. Hansen, Engineer Waimate West County, Taranaki, referring to the Main South Road, says:—''‘This piece of road has been tar-sealed just on four years. In the first place it received the two coats of prepared tar and sand at a cost of about 60/- per chain for the first and 50/- for the second coat. This road is 20 feet wide and carries a lot of very heavy traffic. Besides the ordinary traffic there are five large motor lorries running over it in and out of Hawera twice a day, each lorry usually carries five tons, besides, the weight of the lorry is well over three tons. Last autumn we re-tarred this piece of road at a cost of about 58/per chain. This you will see works out at just under 20/- per chain per year. We have-now over 57 miles of tarred roads, 42 miles tar-sealed, and 15 miles targrouted. The cost of maintaining these roads averages about 15/- per chain per year, that is taking the narrow and wide. We have 4 miles of tarred road that have been down for over four years, about 12 miles that have been down for three years, 25 miles that have been down for

two years, and the balance one year.” Mr. Muggeridge, Engineer to the Hawera County Council, referring to the road between Hawera and Normanby, says:—“This road was top dressed with prepared tar and is giving good results and it cost only £6 10/- per chain. Tar is no use in its raw state and my Council has erected a plant for preparing the tar in proper form to apply to the roads.”

Mr. R. D. Tosswill, Engineer to the Eltham County, Taranaki, says :—“ There are between 40 and 50 miles of tarred roads in this county, they provide a smooth, dustless and waterproof surface, unaffected by motor traffic, thus reducing very considerably the cost of maintenance as a surface spraying every year or so at 20/- to 25/- per chain is all the maintenance required. The initial cost varies according to locality, a sample of one mile and a quarter of 10 feet width having actually cost as followsLabour, £22; tar, 5100 gallons at lid, £233 15/-; chips, 132 yards at 5/6, £36; carting, 666 yards at 1/6, £49 19/-; total, £342.”

Mr. J. C. McLauchlan, Engineer Patea County Council, say^:—“l have to inform you that so far as the ordinary macadam roads are concerned, I find them in this locality quite unsuitable for motor traffic. Tar macadam makes without doubt a very good road, but on account of the plant necessary for this work we are in this county adopting what may be described as tar-grouting instead. The metal is laid in the ordinary way and very well rolled down and then Restar is sprayed on hot over the whole surface of the metal and then blinded with fine clean shingle, then rolled again. Restar is a heavy tar, but good results have been obtained with tar well boiled to remove all the light oils. The above method gives good results and we propose to do several miles of this shortly. Restar costs us about I/-per gallon here and we use

about 60 gallons to the chain for a 14-foot road, and about 2 yards of shingle for blinding. We use from 16 to 20 yards of metal per chain on new roads for about 12 feet width. For our main road work I consider 16 feet is the best width to have, but this is expensive. For roads now metalled and in good shape a spraying with heavy tar and blinded with shingle makes a very good road as the tar seals the surface and prevents the motor traffic from lifting the blinding out of the metal. For this work it is necessary to first sweep the road with a horse broom, and then spray on the tar which must be very hot. However for new work I would recommend you to go in for targrouting your metal as this gives a good road and with regular attention should last for years. It is considered that tar roads require a top dressing about once in two years.”

Mr. John Sturrock, Borough Engineer, Hawera, writes:—“My own opinion is that you would get best results for least money by putting down good metal, well rolled, left to traffic till consolidated, then well swept, coated with gas tar fairly freely, covered with a thin coat of grit, left to set, then coated with one or two coats of good refined tar. The cost of this is much less than for tar macadam roads, and, to my mind, the results for small towns with light traffic, are equally good. The cost of tarring as above in this town, for three coats would be about 9d per square yard. The metal below for say 4 inches of metal 2/-. Total 2/9 as against 5/- per square yard for tar macadam.”

Mr. W. J. Lopdell, Engineer to the Stratford County Council, writes:—“Here in Taranaki we have a very poor class of stone, and one that does not stand the motor traffic. The life of an ordinary macadam road here is about two or three years, when it becomes necessary to

scarify it up and re-surface it with additional metal. Nearly all our roads develop pot holes caused by motor traffic. Our by-roads where there is less motor traffic stand from five to seven years. All our main roads are laid down [to 16 feet in width and 9 inches in depth, the by-roads are 12 feet wide and about the same body of metal crushed down to about 2 1 / 2 gauge. Our metal here costs us about 10/- per yard on an average. We have adopted the system of tar-sealing on most of our by-roads, being considerably cheaper than tar-macadam. The former can be put down for about 30/- per chain on a 12 foot road, one barrel of tar and two yards of light shingle to the chain. A tar macadam road 12 feet wide costs us about £5 per chain plus metal which works out at about 10/- per yard. A second application of top-dressing of course will cost about the same as tar sealing, but I would strongly recommend the latter of the classes of work. Your district should be especially adapted for tar, being warm and having no frosts. I might say that when I was Engineer for the Waimate West County I brought down a loan proposal for £60,000 for tarmacadam roads. I am also laying down about 12 miles per year for the Stratford County. These and the Eltham County roads leave no doubt as to the wisdom of tar sealing on roads.” Mr. W. E- Bush, City Engineer, Auckland writes:—“l may state that tarmacadam has been used with succeSk, particularly in Stanley Street and the Domain Drive. In the first instance it was laid on a thoroughly consolidated hand-packed rubble foundation combined with old road metal and scoria, the tarred macadam, ot course, being nearly six inches thick. The cost of the roadway completed including preparation was 6/9% Per square yard, and the tarred macadam coat cost 3/6 per square yard. The large cost of the foundation is owing

to the fact that the street was made up to a depth of eighteen inches of hard material. In the case of the Domain Drive the tarred macadam was laid 4 inches thick on the old surface of the drive and on the side ditches which had been filled with scoria, this work being carried out for the Exhibition traffic. The cost of the tarred-macadam works on the Domain Drive was about 3/- per square yard exclusive of the tarring and sanding. A great many of the streets of the city have been tarred and sanded with very successful results, but the operation is only successful where you have a good macadamized surface to start with, and wants repeating periodically according to the nature of the traffic and the weather. Its first cost is approximately 4d per square yard and all subsequent coatings 3d.” Mr. W. D. R. McCuddie, City Engineer, Dunedin, writes:—“Tarred macadam is the cheapest form of smooth pavement in the market at the present time. It can be laid to suit almost any traffic. It can be laid on a concrete base, or on ordinary macadam, or Telford base. You cannot tell the difference by looking at the surface after four years use. The advantages of the tar macadam are, it gives a smooth clean surface, it gives a good foothold for horses, motors may run over it at any speed, if attended to with a lick of thin g raw tar and a shake of sand once a year, ” it does not deteriorate, but improves, and is therefore everlasting. Its disadvantages are—lt costs a little more than mud macadam, it allowed to be wet and dirty under traffic it breaks up; if not revived with raw tar in summer as necessary, it becomes brittle and breaks up.”