The Society of Motor Manufacturers and Traders (SMMT) on Wednesday brought together commercial vehicle and bus manufacturers with London's transport policy makers and others around the country at a special event in the capital to discuss the future contribution of commercial vehicles to improving air quality.The Society of Motor Manufacturers and Traders (SMMT) on Wednesday brough together commercial vehicle and bus manufacturers with London's transport policy makers and others around the country at a special event in the capital to discuss the future contribution of commercial vehicles to improving air quality.