A boat tail, a tapering protrusion mounted on the rear of a truck, leads to fuel savings of 7.5 percent. This is due to dramatically-improved aerodynamics, as shown by road tests conducted by the Dutch PART (Platform for Aerodynamic Road Transport) public-private partnership platform.
A boat tail is a tapering protrusion about two metres in length mounted on the rear of a truck. The boat tail had already proved itself during wind tunnel experiments and computer simulations, both conducted at TU Delft, in theory and using small-scale models. Now an articulated lorry fitted with a boat tail has also undergone extensive testing on public highways.
An articulated lorry was driven for a period of one year with a boat tail (of varying length) and one year without a boat tail. The improved aerodynamics, depending on the length of the boat tail, resulted in reduced fuel consumption (and emissions!) of up to 7.5 percent. The optimum boat tail length proved to be two metres.