Gwyn Williams was over taken by the ambulance shortly before the crash in the New Forest and told ITV Meridian what he saw.
He had been driving along the A336 between Brockenhurst and Lyndhurst in the New Forrest.
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The Airports Commission is to publish its report and recommendations on whether an extra runway should be built at Gatwick or Heathrow.
Wednesday morning's weather for the east of the region
Wednesday morning's weather for the west of the region