An avalanche index for roads
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- NGI articles 
Original versionInternational Symposium on Mitigative Measures against Snow Avalanches. Egilsstadir, Iceland 2008. Proceedings
Several methods have been introduced through the years to evaluate avalanche risk along road sections. In 1988, Peter Schaerer introduced Avalanche Hazard Index, a numerical expression of damage and loss as the result of an interaction between snow avalanches and vehicles on a road. Later works by different authors have developed the methodology for risk management and winter road opening of high alpine pass roads. This project is a spin-off of a project conducted by ORlON Consulting for the Icelandic Road Authority. This project describes a simple method to evaluate possible consequences of an avalanche hitting a passing vehicle on a road section. Besides the size, intensity and frequency of avalanches, the severity of the consequences is related to several environmental factors such as the distance from the road body to potentiaIly dangerous terrain features. Such factors may include cliffs and steep banks along fjords, as weIl as steep slopes above the road. In addition, the consequences of an encounter between a vehicle and an avalanche may depend on the probability of a speedy rescue. The factors used are quantified on a scale from 0-5, where the lower values are given the worse case and higher values the more favourable. Test results show that this procedure gives other results than a preliminary assessment suggests in some cases. At a specific avalanche threatened stretch of road site in northern Iceland, a different avalanche path received a higher index value than the one that initiaIly was considered the worst.