Examples of aerodynamic design features Description
Cab to body gap minimalization A large gap between an articulated tractor and trailer unit turns air downwards into the gap which causes a change in pressure and increases drag. Minimising the gap between the cab and trailer on articulated/drawbar vehicles can improve aerodynamic performance.
Cab edge rounding Vehicle drag can be reduced by rounding the front edge of the cab
Cab to body/trailer height equalisation A cab which matches the height of its body/trailer will help reduce drag. Drag can also be decreased further if a lower body is used as this reduces the frontal area of the vehicle.
Air dams These divert air around the sides of the truck and reduce the contribution of the vehicle under-body to the drag
Cab roof deflector This is a flat or contoured plate which can be set at different angles to suit the body. The more the body extends, the more a well-adjusted deflector can offer potential benefits to reduce drag.
Cab roof fairing with or without a collar Roof fairings are three-dimensional mouldings which fit on the cab roof and allow the airflow a smooth transition from the cab roof to the body. A collar when used in conjunction with a suitable roof fairing can bridge the gap between the cab and the body along both sides and the roof.
Cab side fairings These are located at the sides of the rear cab edges and bridge the gap between the cab and body reducing drag.
Cab side-edge turning vanes These small extension pieces usually located on the cab front edges reduce drag as they cover sharp edges and help to reduce the build up of dirt. This feature, however, needs to be ordered from new, if available, and is difficult to retrofit due to the accuracy of size and positioning required.
Tractor/chassis/trailer side panels These cover gaps and therefore limit the interaction of the airflow along the vehicle side with the vehicle chassis.
Tractor chassis filler panels These are most useful for trucks with a large gap between the chassis members behind the cab. The panel is attached to the upper surface of the tractor chassis behind the cab.
Vortex stabiliser/gap seals These have the most impact on trucks with a large gap between cab and body.  A gap seal is mounted on the front face of the body, extending forwards almost to the cab and vertically from the base of the body to the height of the cab. A vortex stabiliser is similar but runs to just three-quarters of the cab height. Vortex stabilisers can also be mounted on the cab collars.
Container front fairing These are mouldings around the edge of the front of body or drawbar trailer. Fairings are either located around the perimeter of the front of the body or cover the entire body front above the level of the cab. Fairings encourage airflow to stay attached at the front of the body roof and sides and reduce drag.
Container roof tapering Drag caused by the rear of a vehicle can be reduced by tapering the rear of the body or trailer.
Trailer roof height reduction Drag can be reduced if the trailer height on articulated vehicles is lower than the tractor. However, the fuel efficiency benefit must be weighed against any loss in revenue from having a smaller load space.
Aerodynamic mirrors Rounding the front face of the mirrors can reduce drag.