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History Resource Centre
Early Road Improvements
The first task in forming a road in a country area was to remove all obstructions. Many of the areas first settled in South Australia were those that were more open because access was easier and roads were more easily formed.
Surveyors were often criticised for their ‘straight line’ roads through impassable country until, in 1864, the Surveyor-General George Woodroofe Goyder threatened dismissal to any who laid ‘impracticable’ roads. In designing their roads, the early road-makers had to consider the limitations of the animal-drawn vehicles. The pull that an animal could exert was not very great, so it was important to make the gradient as flat as possible. A road could include sharp curves provided that sufficient room was allowed for turning. Sharp curves minimised the amount of earth that had to be removed to make cuttings and embankments, an important factor when earthworks were done by hand and horse drawn scoops.
Smoothness, hardness and flatter gradients of road surfaces increased the ability of animals to pull heavy loads. Removing stones and stumps before grading the surface improved the smoothness, but even this proved challenging in some areas of the State. Maintaining a hard surface could be even more difficult to achieve. To form a satisfactory road surface a properly designed road pavement was required.
In country South Australia the climate made road-making a seasonal activity. Stone from suitable sites was quarried and carted to the side of the road in summer when the roads were hard and less likely to be cut up by the heavy drays. The stone was then cracked by hand using ‘knapping’ and ‘spalling’ hammers. The material was spread and formed up by hand and the pavement then compacted by a heavy roller drawn by five heavy horses. City streets were regularly watered to reduce dust and later crude oil was used in the same way. Speed and volume of traffic had not yet become an important consideration. For heavy wagon traffic some roads were laid with steel tracks consisting of sections of rolled steel plate six inches (15.2 cm) wide with a low flange on the inner edge – railway fashion. This method was first used at Port Adelaide then Port Road to Hindmarsh and later between Edithburgh and Lake Fowler for the heavy salt cartage loads.
To reduce costs, modifications to McAdam’s method were used in this State, and continued in some country areas until well into the twentieth century. Two four inch (10cm) layers of stone/metal pieces were laid. Pieces used in the bottom layer had to be small enough to pass through a four inch (10cm) ring and the top Layer to pass through a two and a half inch (6cm) ring. The pavement was ‘blinded with fines’ (loose sand or crushed gravel swept over the stones), and compacted by rolling. Cracking the stones was a job often given to the unemployed in the city; two cubic yards (1.7 cubic metres) was considered a day’s work for which the pay was around four shillings (40c).
The wheels of heavily laden animal drawn vehicles with narrow tyres easily damaged macadam pavement. Even with the Width of Tyres Act of 1867, which limited the load to be carried, a macadam road had a short life and needed frequent repair. Later, the fast moving rubber tyres of motor vehicles created a slight suction as they passed, sucking out the ‘fines’ that bound the macadam together and the stones soon fell apart.
In soft soil the stones were pushed into the ground by the traffic so that the road became impassable. An alternative road was a plank or corduroy road. Planks about six inches (15.2 cm) in diameter were laid transversely across the road on top of two longitudinal planks, and the new gaps filled in with soil.
Around 1880 intersections and gutters in metropolitan areas were sprayed with tar. The process was costly, smelly and required frequent resprays. Imported asphalt was used on footpaths in Adelaide and Gawler, but it was too soft to use on roads that took tyred traffic.
The increase in motorised traffic prompted the need for stronger road surfacing materials and experiments started on the Bay Road (later Anzac Highway) in 1918. Tests of woodblocks, cement concrete, tar paving and asphaltic concrete were tried. Asphaltic concrete proved to be most durable and had an all weather surface. However, it was expensive to lay as suitable mixing and laying equipment was unavailable. Eventually in 1923 the first bituminous concrete plant was imported from the United States and used to resurface a length of the Main North Road.
The bituminous concrete was formed from sand, gravel, filler and bitumen. It was heated to a very high temperature before being dumped by truck onto the macadam or crushed rock base. After raking to an even surface by forks it was rolled to give a layer two inches (5.8cm) thick. This is essentially the hotmix surfacing used at present for most urban arterial roads.
There were other ways bitumen was laid. By mixing it with water into an emulsion it was then sprayed on top of macadam pavement, which it penetrated. Requiring no heating this ‘penetration’ bitumen was useful in the colder Hills areas of South Australia. In hotter rural areas a spray seal was used where the bitumen was heated in kettles before application and a layer of stone or metal chippings spread over the surface to provide a good wearing surface. A development of this method is currently used for little-used roads.
During the 1930s an even cheaper surface was devised. Miles of gravel roads and rubble roads were laid. Surfaced with loose crushed rocks they were reshaped by the newly mechanised graders. The continual reshaping and compaction by the traffic provided a good base for later bituminous works.
As motor vehicle usage increased country roads became popular for day trips. However, with no signposting it was impossible to know where you were at night. The newly formed Automobile Club of South Australia recognised the need for road signage and began producing road warning signs in 1909. Councils continually requested the erection of new signs, but it was not until the Highways and Local Government Department was formed in 1927 that legislation was approved for Government signage on main roads. The newly named Royal Automobile Association (RAA) continued to provide signs for district roads. During the 1960s, 2000 signs were produced in one year by the RAA. After making road signs for fifty years, the expense of converting all signs to metric measurements proved too much for the RAA and they stopped production of road signs in 1970, with the Highways Department assuming this responisibility.
Posts carrying signs have changed from heavy, bulky jarrah to light-weight galvanised metal. Instead of carved and painted numbers on wood the signs now feature reflective pressure sensitive material on backing plates impregnated with millions of tiny glass beads
After the 1930s, improvements in road-making were largely in design rather than construction. The greater speed of the motor vehicle made the very tight curves and narrow widths of the old roads dangerous and increased the likelihood of accidents. Guard-rails were installed at the roadsides in the Adelaide Hills in 1927. Later warning signs were erected at danger spots and centre lines were painted at curves.
At his retirement in 1986, Department employee Keith Thomas recalled that when he joined the Pavement Marking Section in 1960 some of the line marking, arrows and messages were still done with a brush.