In simple terms, this mean the 'uninsured', were riding in a vehicle which did not have a current road tax sticker. Payment of the annual road tax has to be supported by an insurance reciept available through agents at the vehicle tax issuing office. The insurance ensures medical aid to the vehicle pax but is limited. The insurance covers only people NOT vehicle damage.
Many expat vehicle owners opt to get First Class cover policies which cover their vehicle, pax and third parties.