DIAMOND GRINDING'S ROLE IN INCREASING SAFETY ON AN AUSTRALIAN HIGHWAY

One decade later, no black ice incidents reported

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Ten years ago, Forty Bends, a section of the Great Western Highway in the Blue Mountains west of Sydney, Australia, had a persistent and dangerous problem. During winter, ambient temperatures regularly dropped below freezing, causing a thin, nearly invisible layer of ice to form on the dark-colored asphalt surface—a phenomenon known as black ice. Because the ice is transparent, it allows the dark pavement beneath to show through, often appearing simply as a wet road. For drivers, the result was a sudden, unexpected loss of traction.

Initial resistance to concrete

When the highway was being upgraded to a dual carriageway, the pavement design engineer did not initially consider a concrete pavement. Concerns centered on whether concrete could achieve sufficient surface texture depth and whether the piecemeal traffic switches required during construction would result in an unacceptably rough riding surface.

Those concerns were addressed directly. Concrete's ability to retain heat during daylight hours in winter was acknowledged as a meaningful advantage. It was also confirmed that conventional diamond grinding (CDG) could achieve the required surface texture depth while delivering a smooth surface that met ride quality limits. With those assurances in place, a Jointed Plain Concrete Pavement (JPCP) was selected for the project.

CDG was applied across the carriageway to a minimum of 300 mm past the edge lane lines, with lane widths of 3.5 meters. The curved road alignment did not require the lane line enhancements commonly used in the United States. Standard raised pavement markers between dashed lines were installed, as snowfall is uncommon at this location. Diamond grinding was carried out by former IGGA contracting member Seovic Civil Engineering (later acquired by member the Dowsing Group). 

The results

The Forty Bends section of the Great Western Highway has now been operational for more than a decade. In that time, no black ice vehicle incidents have been recorded—an outcome that speaks directly to the effectiveness of JPCP combined with diamond grinding in cold-weather, high-risk pavement environments.

This project demonstrates that pavement design engineers’ reservations about concrete pavement performance can be resolved through sound technical analysis, and that diamond grinding is a proven tool for achieving both safety and ride quality outcomes in demanding conditions for a new concrete pavement subject to traffic switches. Reach out to learn how diamond grinding can deliver a smooth and safer pavement surface: https://www.igga.net/contact-us