Fig. 3From: Improving volcanic ash fragility functions through laboratory studies: example of surface transportation networksImpact states for expected ground-related disruption to transportation as a function of ash thickness. The existing impact states (shown in black) were derived from qualitative post-eruption impact assessments and limited semi-quantitative field studies (adapted from Wilson et al. 2017). Impact states that were improved in this study are shown in red Back to article page