139 heavy goods vehicles (HGVs), 59 public service vehicles (PSVs) and 15 light duty vehicles were sampled at random from the UK in-service fleet and subjected to free acceleration smoke (FAS) tests in accordance with regulation ECE 24. It was estimated that approximately 50% would emit smoke levels in excess of the conformity of production regulations, and this would contribute 80% of the total smoke emissions from heavy vehicles under free acceleration conditions. Turbocharged engines emit considerably more smoke during FAS tests than do naturally aspirated engines. HGVs and PSVs emit approximately equal amounts of smoke. There is evidence to suggest that smoke levels as determined by FAS tests deteriorate between services for HGVs, although the average annual level of smoke does not vary significantly over the lifetime of the vehicle. Light duty diesel vans emit considerably more smoke than the HGV fleet. This is probably due to their exemption from the annual smoke test. It is possible that police spot checks, using current sampling criteria, could be used for checking compliance with future in-service smoke standards.
Abstract