This meant that vehicles were unable to gain traction, and even four-wheel drive vehicles were sometimes unable to use the roads when thicknesses exceeded 100 mm.
Anitha et al. (2001) assessed the effect of parameters such as layer thickness, road width and speed deposition on the quality of the prototypes using the Taguchi technique.
Observations from Barnard (2009), who conducted a number of semi-quantitative field experiments on Mt. Etna, Italy, also informed ISs for road transportation where thicknesses exceed 50 mm.
The designed layer thicknesses of the road were then compared with measured thickness data.
In the temperate zone the major issue facing road users was the thickness of ash on the road.
Fluctuating intensities of road transportation disruption with thickness have not been identified in the past, highlighting the importance of laboratory testing and the complexities that can be involved in determining accurate IS thresholds.
Although the impacts of reduced visibility (accounted for separately) may mask such effects overall, we suggest particularly elevated disruption to road transportation from ash thicknesses between ~ 2.5 and 5.0 mm.
The enhanced stability would result in longer service life and smaller thickness sections for road construction.
With these improvements, the thickness of concrete road for a particular studied loading condition can be reduced by 12.5 mm.
Because road traction reductions occur at thicknesses as low as 1 mm, and road markings are obscured at thicknesses as low as 0.5 mm (Blong 1984; Magill et al. 2013; Blake et al. 2016), clean-up operations on roads are often initiated at thicknesses between 0.5 and 1 mm (Hayes et al. 2015).
