Abstract: A streamlining apparatus for the cab of a heavy transport vehicle has a transverse section smaller than that of the body of the load transported and comprises an air-flow deflector formed by a front part and two lateral rear parts. The apparatus further comprises an element adapted to engage the roof of the cab and which is connected to the front part of the deflector, this element comprising lateral parts, which, longitudinally, substantially conform to an upper surface of the cab, and a front part which extends to at least the level of the front transverse roof edge of the cab, with respect to both the downward and forward extents of the cab.