The addition of external equipment or additional load to the vehicles is rather common nowadays and is mostly related to leisure activities. Such equipment may include trailers, campers, roof boxes, bicycle racks, ski boxes, or even additional load inside the cabin.  All of these have an impact on vehicle emissions in many ways. First, they add to the vehicle weight. They also deteriorate the aerodynamic resistance due to the increased frontal area and drag coefficient. Towing a trailer or a camper also increases the rolling resistance due to the extra wheels slipping on the road. All of these effects result in higher engine loads, which in turn may result in some of the emissions control systems to operate outside their optimal range. In general, the heavier and bigger the external equipment is, the greater the impact on the emissions will be. Therefore, it is suggested to remove these items when not in use. In all other instances, a smooth driving style allows the driver to avoid a significant increase in pollutant emissions.