This paper examines two methods for risk evaluation in a case study for the Milford Road, New Zealand. These results are then used to quantify the effect of the avalanche programme in reducing the risk and enable clear comparisons with other roads around the world. The Milford Road (State Highway 94) between Te Anau and Milford Sound, is the only public highway with a significant avalanche problem in New Zealand. Significant avalanching occurs on the Milford Road, because of the oversteepened, glacially carved terrain combined with very heavy precipitation that exceeds 8000 mm per year. Milford Sound, at the end of the Milford Road, has been recognized as a world heritage area, and is becoming an increasingly popular tourist destination. Over 400,000 people visit Milford Sound annually and the majority of these arrive by road. Furthermore, the daily traffic flow is strongly tidal, causing periods of very high traffic concentrations in the mornings and the evenings. The Transit New Zealand Milford Road Avalanche Programme has been responsible for managing the avalanche risk to these travelers, since its inception in 1983. With continually increasing traffic flow and avalanche risk management, we examine the present avalanche risk, as described by the Avalanche Hazard Index (AHI) in common use in North America, and the Probability of Death to Individuals (PDI) method more commonly used in Europe. We also comment on the sensitivity of these methods to the various assumptions made in the analysis and quantify the effect of various control and management strategies on the avalanche risk. We conclude with some practical suggestions which have successfully been used to minimise the risk on the road.
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