Kent Police and the Health and Safety Executive are understood to have identified a reversing lorry as key to the death of a 38-year-old Costain surveyor on a road project in Kent.
Richard Caddock was killed last Tuesday on the M25 site near Dartford where Costain is working on a £62m road widening scheme for the Highways Agency.
The investigation is thought to be looking at whether Caddock heard the lorry above the noise of passing motorway traffic.
Almost 10% of deaths on construction sites have been caused by moving vehicles, according to HSE figures.
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