The instantaneous moving mode of sand mass is divided into 4 types, namely: rolling, jumping, suspending, and running away, when the wind speed reaches the threshold velocity of sand-driving wind.

He said the skies reminded him of those of his native Algeria — bright, wind-swept, unobstructed — and he was driving “home” from Paris when he had his fatal crash.

Road surface, other traffic, wind noise and driving speed all contributed to the cacophony.