THE ROADING PROBLEM

Otago Witness, Issue 3396, 16 April 1919, Page 7

THE ROADING PROBLEM

TARRED AND CONCRETE ROADS.

THE METHODS IN TARANAKI

In a previous issue wo published the introductory portion of the report furnished by Mr B. B. Couston, C.E., to the Otago Motor Club on the results of his inspection of the tarred roads in Taranaki and the concrete pavements in Wellington and Auckland.- Continuing his report, Mr Couston describes particularly the system of road construction that has been adopted in Taranaki. Ho writes:

I shall now endeavour to give you the methods adopted in some of the counties and boroughs and their engineers' estimates of the cost of work. PRACTICE IN ELTHAM COUNTY.

The practice in Eltham County is to form the road as for ordinary water-bound macadam, using 2£in metal blinded with a little clay and then stone dust, and thoroughly consolidate by rolling. This road 13 left to be trafficked for six months and any inequalities taken out as they develop. The road is thoroughly swept with a horse-sweeper and cleaned with hand brooms, and any small potholes in the surface made good with crusher chips. Tar is applied from a portable boiler, fitted with tar pump, hose, and nozzle, the latter being manipulated by hand. .Crusher chips up to gin gauge are spread from drays following, and the road is left for traffic to consolidate. Six months later the road is brushed again and sprayed with tar, and for gritting material sand and small pea-size stones are employed. After 12 months the road is again sprayed, and the year after that it may or may not need to bo done again. *'or a road 10ft in width the first coating takes 50 gallons of tar and 2£yds of chips to the chain, and the second coating 15 gallons of tar and fyd of sand. Mr Tosswill is the county engineer, and has undoubtedly some, of the finest roads in New Zealand. The county has a _ rateable value of two million, and the rate is in the .pound. The plant alone is .worth an inspection. They have three motor lorries, stone crusher, tar sprayer, and road roller and scarifier, and a large tar-boiling depot equipped with every practical convenience. The motor lorry is fitted with the "ready tipping gear," which enables a load of three tons to be handled by one man and tipped to any angle desired up to 45deg. WAIMATE WEST COUNTY. Waimate West is a small county of 72 square miles, with a capital value of about one and a-half millions. Its nearest connection to the railway is eight miles, and there are nine or 10 heavy motor lorries over its main road every day. and this road also carries a considerable amount of through traffic from an adjoining county. It is solely a dairying district, and the motor and other traffic became so heavy that it was found impossible to make and maintain ordinary macadam roads out of the rates, so they decided to tar the whole of their roads, and raised a loan of £60,000, and have now 57 miles of this type of road constructed, some of which have been down over I four years. Their engineer _ (Mr Hansen) estimates the cost of maintaining these roads averaging the wide with the narrow and the main with the by-roads, at 13s per chain per year. There are two" ridings, and the rate is lid in one riding and If d in the other. There is no special rate, and I was asked particularly to mention also there are no toll gates. They adopted the two different systems of tar-grouting and tar-sealing, and their engineer expressed the opinion that the former gives much, better results, and costs only 20s per chain more than the latter. Their method of tar-grouting was to metal or remetal the road as for ordinary macadam, spray the tar evenly over the surface, and cover with crusher chips or good clean river-bed shingle. The road is then opened to traffic for a few days before' giving" the second coat Prior to this second coating the road is swept with a horse brush, leaving any surplus shingle at the edge of the tarred macadam, and this material is used the second time when covering with shingle. The road is then ready for traffic, but subsequent care must be taken to keep any bare patches of tar covered.

The Waimate West County purchase -what is known as tar No. ' 1 from the Eestar Company, and from this their engineer prepares his own binder by further distilling the tar with 4-0 to 50 hours boiling, according to the rate_ it is fired, and adding some vegetable oil and resin. The cost of the first coat is about 9d per square yard, and of the second about 6£d. - . For tar-sealing the same method is employed as in Eltham, County, except that Waimate uses shingle for gritting material, and for a : 12ft road the quantity of tar is 40 gallons to the chain. They give the eecond coat of from 25 to 30 gallons to the chain the following season, and thereafter the road does not require further attention for two, or in some instances three, years. The first coat costs 8d and the second per square yard. Their engineer particularly emphasised the necessity for careful selection of the tar and for using this very hot, and spraying evenly without allowing any to drip in patches on the road. What they refer to as shingle wo would term" pea gravel, and it must be- clean and of a sharp, gritty nature, and spread on the tar lightly at first, and not thrown on in heaps or thick, as this tends to push the tar up into pockets, and causes humps to form on the road This county council, in addition to owning an up-to-date crushing plant, have two steam rollers, a five-ton motor lorry, which is used in delivering tar hot from the boilers to the sprayer, and for hauling the shingle, and they have two large tar boilers, each of 1200-gallon capacity, and a horsedrawn tar sprayer holding 300 gallons. The motor lorry has taken the place of four four-horse teams. Instead of ordinary block drays, where thoy use horses for traction, light spring tip-drays, drawn by fast horses, are employed in the work. One section of road was pointed out to me on which the county spent £IOOO a mile on repairs before tho tar treatment days, and the road was worn out and done in two years. Four years ago this road was resurfaced and tar-grouted 20ft wide, and {t has only had one coat of top-dressing fiinoe. This road runs on six miles towards ppunake, and it is a splendid example of rwnat a main road should bo. PATEA COUNTY. Mr MlLachlan, engineer to P.ttea County, tnpplied me -with some figures that illustrate the efforts that are being concon-

trated on the main road improvement. This county has a capital value of three millions and a |d rate, and has,already laid down nine miles out of 26 of its main road with tar-grouted or tar-sealed top coruse. This work ha 3 been done out of revenue, and the policy of the county is to spend onehalf of the rates on the main road and the other half on tho side roads.

A length of tar-grouted macadam was in course of construction on tho day of my visit Th& road had boon scarified by machine, and the subgrade brought to proper section with the road grader, and then consolidated with the steam roller. The stone for macadam was being crushed on the roadside, the plant working at- an elevation above the road so that the metal could be supplied to drays from a. chute. Tho tar had been distributed at depots along tho road, and pits dug at suitable places for heating. A special design of low-wheeled cart was employed for running out the tar to the sprayer. The chips which come from the Belmont quarry near 'the Lower Hutt had been stored in heaps preparatory to tho work. On the one stretch under construction wore to bo seen the old gravelled macadam road, the subgrade prepared for the new macadam* this macadam laid and rolled, the same after being tar-grouted, and the completed after the spreading of chips._ The example aptly illustrated the rapidity with which this class of. work • can be carried out with modern appliances. In tar-sealing work there is no difficulty in completing half a mile of 15ft road in a day, and this when boiling the tar in drums on the roadside.

ESTIMATES OF OTHER ENGINEERS

Mr Wrigiffc, engineer to Kairanga County Council, has tar-grouted and tar-sealed roads. For an 18ft road he uses 60 gallons of tar and 2f yds of chips for the first coat, and 44 gallons of tar and lfyds of chips for the second coat, for the third and fourth coatings of tar his experience is that one gallon covers six square yards. For tar-painting a good waterbound macadam road, he considers 30 gallons to the chain sufficient, and estimates the cost at £3 10s per chain. Mr Davies, engineer to Patea Borough, estimates the cost of similar roads in his district with tar at 12£d and chips at 17s 6d to be £4 a chain. Wanganui Borough has 10 miles of tar macadam road gnerally laid on old pit gravel foundation. In some instances Mr W. C. Stavely has adopted the multiple penetration method of grouting. The metal or screened gravel is laid in two courses, and each course grouted separately. Some work that was being carried out in the borough on the day of my visit afforded an illustration of what an excellent class of road can be constructed in tar-grouting using shingle similar to that in many of the dredge tailing heaps of Central Otago. Mr Crow, engineer to the Restar Company, supplied mo with estimates for the tar treatment of macadam roads in various degress of repair, which, though they may not be exactly applicable in every district, five a good idea of the cost of treating ifferent roads. Estimate No. 1. For tar-sealing a waterbound road in good state of repair and with at least 6in of well-consolidated metal.'' Length, one mile; width, 15ft. Priming Restar, 4400 gallons at 9d ... ..,£165 . Heavy Restar, 2203 gallons, &i' Is -... ... HOSweeping 5 Spraying and patching 30 Blinding 70 Contingencies £4lB Estimate No. 2. For a road similar to No. 1, but much potholed and worn to sin of metal in poor shape. Length, one mile; width, 15ft. Surface, 8800 square yards; Scarifying ... £ 9 Spreading metal' 6 Labour on tar 4 370 yards metal, at 13s 240 Blinding 49 6500 grouting Restar, at 9d ... 248 Flush coat Restar 200 Rolling 5 Contingencies 77 £B3B TAR MACADAM ROADS. For instances of tar macadam roads, I might illustrate many borough councils, but will give as typical examples the practice of the engineers of Hawera Borough and Palmerston North. For the information regarding Hawera I am indebted to Mr J. Sturrock. and for Palmerston North to Mr S. Jickell. HAWERA BOROUGH. Hawera is a small borough with a population of 3600, but its progressive spirit may bo judged from the facts that it has laid down four miles of tar macadam road, one and a-half miles of tar-painted roads, 20 miles of single-path tar macadam footpath with concrete kerb and channels, and has, in addition, a gravitation water supply from Kapuni Creek, about 11 miles distant, a water tower to boost up the pressure in the mains at times of fire, 15 miles of water retriculation, and a sewerage system with 14 miles of sowers in the borough and two miles of gravitation outfall sewer to the sea. The town has an electric light supply and gas supply, but these are run by companies. A few years ago a loan proposal was carried for £36,000, principally for street imorovement works. A number of the streets were formed in tar macadam ; using the proprietory tar preparation called Tarvia. The method of construction was to scarify, plough, and grade the • old excessive crowns to a reasonable camber, the old metal being screened from dirt and used again. Four inches of 2£in metal were then spread, rolled, blinded, and left to traffic to consolidate. When consolidated a layer 3ir. thick of 2Ain to lin tar macadam was spread and rolled, then blinded with £in tar macadam and left to traffic till hai-d. The surface then washed and brushed clean and tar painted, and immediately covered with a layer of gin thick of £in tar macadam, blinded on top with iin macadam. This, in turn, was left to traffic, and when set was liberally coated with tar and gritted sparingly. Tho cost for re-forming crown and metal foundations, tar macadam and tar painting, was 5s per square yard. The metal and chips come from Belmont and cost 12s 6d a yard, the larvia Is 43d per gallon, tar 9d to lOd per gallon, screened shinglo 12s per yard. Mr Sturrock has every convenience provided for heating and mixing the tar. The mixer is a Ransoms Yelir-Mehr machine electrically driven and ied by a bucket

elevator. It 3 capacity is nine cubio yards per hour, and the mixer is so placed that tho drays back in right below and receive their loads direct from the mixer. The cost of the machine, erected complete with motor and elevator, was less than £SOO. PALMERSTON NORTH. Mr Jickell, of Palmerston North, is one of tho strongest advocates of the tar treatment of roads. Ho first put 3 the roads in thorough order with ordinary macadam and leaves them to bo consolidated by traffio for six months, after which he again touches up any weakness. Then the topstono only is moved by the scarifier and l£in of tarred screenings, 18 months to two years old, is spread on top first lightly rolled and then heavily rolled. After six- weeks this surface is tarred and sanded two coats. Local gasworks tar is used after boiling for six hours. The streets round the Square were done in this manner, and have an excellent surface. The cost without the regrading was 2s lCd per square yard, and the work would cost about 3s 9d. at the present day. For a newstreet in tar-macadam he used tarred 2in metal 7in deep, top dressed with lin of tarred screenings, then a final coat of tar and sand. This cost before the war 4s 5d per square yard, and would cost nearly 6s now.

Several of the old macadam streets in Palmerston North were tar-painted as follows: —They were first scarified, rolled and watered slightly, then surfaced with a coat of tar by means of the sprayer with pressure of 701 b per square inch; this was left to set and not sauded, then another coat of tar, and this sanded. Tho work cost 3J,d per square yard for tarring and sanding only, but present price would bo 4|d. • The streets in the Square have been topdressed every two years, and the side streets once in three years. One of Mr Jickell's mottos is "to tar when the sun shines." In Pamerston North they never water the streets that are tar treated; they are swept every morning. Mr Jickell briefly states the whole question of maintenance to one of vigilance, the stitch in time is the factor that counts, and holes must not be permitted to develop. LEVIN TOWNSHIP. I do not think any object would be served in giving further instances, but as I was asked to note particularly the township of Levin I broke journey there on the way up. Levin is a small township with a population of 1800, and Oxford street, its main street, is the main north road, and the traffic is very heavy. It was tarred and sanded full width between the channels some years ago with three coats of local gasworks tar.at a cost of s£d per square yard, and has subsequently been maintained with an annual top dressing of tar applied by hand at a cost of 2d per square yard per annum. The tarred surface is a marked contrast to tho ravelled gravel formation of the main road not so treated and which the borough now proposes to attend. This little township, I might add, has borrowed for various publio works £36,0*00.

WHY TARANAKI ADOPTED TARRED ROADS.

It was the poor quality of the metal or shingle available in Taranoki, combined with the wet climate and the utter impossibility of maintaining roads constructed in waterbound macadam against the ever-increasing and much diversified traffic that forced the county councils to adopt some new form of wearing surface for their roads. The local bodies experimented for years with A-arious methods of tar sealing and tar grouting and with every variety of tar, both imported and of local manufacture. There were failures but these did not deter from perseverance, and whilst there are some roads where the mistakes of initial treatment are still apparent, there can be no question whatever that a wearing surface infinitely superior to ordinary macadam has been obtained and that the roads are giving entire satisfaction. They are clean, hard, as smooth almost as a billiard table, and a delight to motor over. WHAT THE RATEPAYERS SAT. The words of the chairman of the Waimate West County expresses the general attitude of that important class, the ratepayers. "It took a, lot to persuade our people to sanction this policy, but it would take much more to persuade them to abandon it now they have proved its worth." - Another example illustrating the attitude of the ratepayer is the request of the ratepayers in Oeo Riding of Egmont Counfcv to have their district merged in Waimate West County. The meeting of representatives was on the day of my visit, and I quote a few extracts from tho Hawera Star: They were there that day to urge the council to move quickly and bring about the merger that they desired, and he understood that all the ratepayers in the Oeo Riding-, with one exception, were desirous for this to be done. They had been paying a rate of l|d, and they were led to believe that this would be increased to 2d during the ensuing year, and he contended that they were not getting the expenditure on their roads that they should have. They appreciated very keenly the splendid manner in which the Waimate West councillors had administered their funds and the magnificent roads they had. "We want to be members of such a good county," concluded Mr Bennett. The Chairman said_ that Mr Bennett had stressed tho point that Waimate

Council had not urged forward this movement. It was not the council's policy to do so. They always endeavoured to work amicably with neighbouring councils, and had not sought to get in ratepayers from any other county; they were quite satisfied to go on with the county as it was. But, seeing that a petition, practically unanimous, had been presented to the council two months ago, tho counoil would not have_ been doing its duty if it had not recognised that petition. • Apparently there was only one course now open if the Waimate West Council agreed to accede to the request of the petitioners, and that- was to ask for a commission to ho set up to adjudicate

upon tho matter. There were one or two aspects of this case that must not be lost sight of. The Waimate West County Council had raised a loan of £60,000 to put all their roads in good order and tar them. They had done a considerable portion of this work, and they had to continue it when they could arrange for the balance between the £4S,OCQ already received and the' £60,000 authorised. Tho Government informed the council 12 months ago that under new regulations no further advances could be made under the old authority, but that another vote of the ratepayers would have to bo taken. The council intended to go on with the matter and place; the Issue before the ratepayers

to raiso this balance of £15,000. This, they anticipated, would complete all their roads, including tar-sealing, and he might here remark that without tar-seal-ing they could not maintain their roads under a 2d or 3d rate under present traffio conditions. But with tar-sealed roads maintenance would be only onethird or pne-half the oost of the old system. QUALITY OF TAR

I have refrained from making comment on tho various grades of tar and tar products that have been employed in.different counties and boroughs, because I realise that actual experience alone will prove tho rel&tivo economy of the binders suitable for the material and traffio of the road. Most of the tar in Taranaki is obtained from the Restar Company (Ltd.), and is either distilled by them to road board specifications Nos. 1 and 2, or supplied in the grade designated "Restar." In Hawera borough the engineer has experimented with Union asphalt road binder, which is stated to contain a high percentage of pure bitumen, and he found it lasted rather more than twice as long as a street treated with refined tar to road board specification. Engineers recognise that tar and tar products have their limitations, and they look for some material with greater weather resisting property. THE DEVELOPMENT OF TAR-SEALED ROADS. It is advisable when considering the question of the binder to recollect the various stages of development that led to_ its use. It was early . recognised that if waterbound macadam were kept moist by sprinkling with water, rapid disintegration under light machine traffic travelling at medium speed was prevented, but for long stretches of country road the cost of such treatment was prohibitive, and, moreover, where the speed was high, sprinkling did not protect a plain macadam. _ Experiments were then made with such binders as calcium chloride, and these kept the dust down for a longer period by virtue of their property of absorbing moisture from. the atmosrjhere and condensing it on the road surface. Such treatment, however, merely prevented the fine surface dust from being blown away, but did not build up the road or form a wearing cushion to protect the stone, and such palliatives besides being efficient for a short time only, had the tendency of causing during the winter months an abnormal quantity of sticky mud, and moreover had a disintegrating action upon the macadam surface. . Light oils and light tars proved efficient as dust layers when properly distributed with fine sriray pressure machines, but their effective life was short, and waterbound macadam so treated could not be preserved under high speed motor car traffic. The fourth stage of development was bituminous flush coat applied hot to the rough, clean, dry surface of a macadam road, and for which, as I have previously stated, asphalts, orude and refined tars and combinations of refined tars and asphalts have been used. THE LIFE OF A BINDER.

Tho life of a bituminous surface and its economical use depend largely upon traffic conditions and the nature of construction and material. With the heavier grades of tar and for a road subjected to normal traffic re-treatment is necessary every one or two years. A weil-constructed surface of this kind resembles asphalt. It is impervious and easily cleaned. It protects the macadam from ravelling, yields no dust due to abrasion, forms a' surface which takes the Wear of the traffic from the large stone fragments, and gives a good appearance. Its disadvantages are that it cannot be laid in wet weather, and that. like asphalt, it is slippery on steep grades. A disadvantage often stated is that unless evenly spread a rough, bumpy road results. This is readily admitted in Taranaki, but is overcome by laying evenly and talcing proper precautions at every stage of the work.

ULTIMATE LIFE OF THE ROAD. So far as the life of the road is concerned some engineers claim that by successive applications of a fhish coat tho road can be maintained indefinitely, others give tho read a life of ]5 to 20 years. One point I would emphasise is that whilst the road is to a high degree suitable for motor traffic, and to a lesser degree for mixed motor and horse-drawn traffic, tho former must predominate where the traffic is considerable, in order to iron out satisfactorily the calk, holes caused by the horse. TAR-GROUTED AND TAR-MACADAM ROADS.

The fifth stage of development is the bituminous macadam pavement either constructed by the penetration method or by the mixing method. The penetration method is that generally employed on rural highways both for reasons of convenience, and cost. The necessity of a seal coat is determined by the traffic conditions. Tho macadam without the flush coat gives good footing on any grade that is suitable for heavy hauling, and is more easy to repair for small depressions' and rut?. On the other hand it is not waterproof when first constructed, and wears more rapidly than the flush coat construction, and consequently costs more to maintain. There is no doubt these constructions are good, and a great advance over plain macadam, but they have disadvantages which must not be overlooked.