In the 20th century, the major achievement has probably been the Australian-New Zealand development of the spray and chip seal method of pavement construction for a wide range of conditions and traffic. This method is much cheaper but just as effective as many of the alternatives used in other countries. The analogy with the earlier use of McAdam and Telford methods is strong. The history of roads shows how much of the technology used in our growing road system was necessarily derived from the old world. Given the communications of the time, it sometimes arrived in and spread through Australia with surprising alacrity.

The impact of road construction and alignment on the environment is now a sensitive issue throughout the country. A specific example of where community needs have been given great consideration by the Department of Main Roads, W.A. and their consultants Gutteridge Haskins & Davey is the Munjina Gorge project in the northwest of Western Australia. The new national highway from Newman to Port Hedland passes through the Hamersley National Park near Wittenoom. Within the park, the road traverses a gorge which requires a 40 m deep rock cut leading to a 35 m high embankment. Since environmental considerations are paramount, the traditional V-cut was rejected and a sculptured shape adopted which would mirror the natural forms in the surrounding gorges. The sides of the cut will have near vertical cliffs, rounded edges and slopes shaped similar to scree slopes. The width of the cut varies in an irregular pattern without straight lines, and where natural depressions cross, the cut has been returned in 'blind valleys' which have a waterfall configuration at the head.

Stability considerations were carefully evaluated and the levels and slopes of various features adjusted to ensure stability. A berm was found to be necessary in some areas, but this was also brought into an undulating form. It is accepted that there will be some weathering and minor falls in the first few years, but this will assist the natural look which is so essential with the lack of natural revegetation. Wide drainage courses at the base of the cut are detailed to accommodate fallen material without danger to traffic. Undulating mounds will occupy larger areas of the floor of the cut, positioned to create meandering drainage lines in some areas.

Pre-splitting of the exposed sides of the cut would have caused artificial shapes and visible drill holes and hence the last few metres of cut will be pulled away by machine, allowing the rock to break on its natural jointing patterns.

The history of Australian roads must be seen in the context of a vast but sparsely settled continent, with a small but technically competent population and with little excess wealth. Road makers in Australia have always faced adverse conditions, conditions which make their achievements even more meritorious than might at first appear.

Australian Academy of Technological Sciences and Engineering