Traditionally, treatment of frost, ice and snow on New Zealand roads has involved spreading of mineral grit on the affected areas but this has disadvantages. Common salt was used as a de-icing agent until the early 1980s when public concerns about vehicle corrosion led to its use being discontinued. A major review of options for de-icing of state highways was then carried out in 1996 by Transit New Zealand, to consider de-icing agents commonly used overseas. Calcium Magnesium Acetate (CMA) was deemed most suitable for New Zealand conditions and had lowest risk regarding skid resistance compared with other de-icing agents used in Europe and North America. However crashes occurring after CMA applications raised concerns about this risk.
This study was undertaken during the winter of 2004 on Coastal and Central Otago roads to quantify the magnitude and extent of changes to skid resistance brought about by the de-icing agent CMA, and to assess the effects of migration of CMA through tracking by vehicles on those roads.
The research was based around an on-road test programme comprising skid resistance measurements using a British Pendulum Tester (BPT), the Central Laboratories’ GripTester, and a car instrumented for Locked-Wheel-Braking (LWB) tests.
Keywords: braking distance, British Pendulum Tester, BPT, Calcium Magnesium Acetate, CMA, frost, GripTester, ice, locked wheel braking, skid resistance, roads, traffic