Wagon body module for forming at least a portion of a head portion of a wagon body of a vehicle supported on at least one running gear, in particular a rail vehicle for high-speed traffic, having - a flow guiding device, - said wagon body defining a vehicle longitudinal direction, a vehicle transverse direction and a vehicle height direction, - said head portion being configured to form a leading free vehicle end (101.1) during normal operation of said vehicle, - said flow guiding device being configured to be arranged, at a lower side (102.2) of said wagon body, in said vehicle longitudinal direction between said free vehicle end (101.1) and a leading end of a running gear cutout of said wagon body, the cutout receiving said running gear associated with said free vehicle end (101.1), and - said flow guiding device being configured to influence, during operation of said vehicle, an air flow which flows over said lower side (102.2) of said wagon body from said free vehicle end (101.1) towards said running gear cutout, - said flow guiding device has a guiding portion (109.1) adjoining said flow separation edge at said leading end of said running gear cutout and reducing, in said vehicle height direction, a free flow cross-section available for said air flow towards said flow separation edge in such a manner that, in a region of said flow separation edge by means of a deflection region, a downwardly directed main flow direction is imposed to said air flow, which is inclined relative to said vehicle longitudinal direction by at least 3°, preferably at least 4°, more preferably at least 6°, characterized in that - said flow guiding device has a diffuser portion (109.3) located upstream of said guiding portion (109.1), extending between said free vehicle end (101.1) and said guiding portion (109.1) and increasing, in said vehicle height direction, a free flow cross-section available for said air flow towards said flow separation edge. - a flow guiding device, - said wagon body defining a vehicle longitudinal direction, a vehicle transverse direction and a vehicle height direction, - said head portion being configured to form a leading free vehicle end (101.1) during normal operation of said vehicle, - said flow guiding device being configured to be arranged, at a lower side (102.2) of said wagon body, in said vehicle longitudinal direction between said free vehicle end (101.1) and a leading end of a running gear cutout of said wagon body, the cutout receiving said running gear associated with said free vehicle end (101.1), and - said flow guiding device being configured to influence, during operation of said vehicle, an air flow which flows over said lower side (102.2) of said wagon body from said free vehicle end (101.1) towards said running gear cutout, - said flow guiding device has a guiding portion (109.1) adjoining said flow separation edge at said leading end of said running gear cutout and reducing, in said vehicle height direction, a free flow cross-section available for said air flow towards said flow separation edge in such a manner that, in a region of said flow separation edge by means of a deflection region, a downwardly directed main flow direction is imposed to said air flow, which is inclined relative to said vehicle longitudinal direction by at least 3°, preferably at least 4°, more preferably at least 6°, - said flow guiding device has a diffuser portion (109.3) located upstream of said guiding portion (109.1), extending between said free vehicle end (101.1) and said guiding portion (109.1) and increasing, in said vehicle height direction, a free flow cross-section available for said air flow towards said flow separation edge.