A method for detecting wheels of a vehicle on a road , said wheels being visible on a side of the vehicle , comprising, for a first position of the vehicle on the road : directing a vehicle classification sensor from a sensor position (P VCS ), in a given coordinate system , onto a section of the road and recording , with the vehicle classification sensor , a 3D representation of the vehicle or of a part of the vehicle passing the section , which part comprises a portion of the vehicle side ; directing a first camera from a first camera position (P CAM ), in the given coordinate system , onto the section and recording a source 2D image , comprised of pixels (18 i ) representing points in a source 2D image plane , of at least a lower portion of said vehicle side , said camera being calibrated by a mapping between world points in the given coordinate system and image points in said source 2D image plane ; determining , in the given coordinate system , a bounding box circumscribing the 3D representation , a side of the bounding box corresponding to said vehicle side , and the four corner points (29 1 - 29 4 ) of said bounding box side ; identifying , using said mapping, image points of said corner points (29 1 - 29 4 ) in said source 2D image plane as source corner image points (29 1 ' - 29 4 '); defining a destination 2D image plane parallel to the bounding box side in the coordinate system , and the four corner points of a rectangle (27") in the destination 2D image plane as destination corner image points (29 1 " - 29 4 "); calculating a projective transformation between the source corner image points (29 1 ' - 29 4 ') and the destination corner image points (29 1 " - 29 4 "); transforming , using the projective transformation, source 2D image pixels (18 i ) to destination 2D image pixels (33 i ) of a first destination 2D image ; and detecting the wheels of the vehicle using the first destination 2D image by means of an image recognition process. directing a vehicle classification sensor from a sensor position (P VCS ), in a given coordinate system , onto a section of the road and recording , with the vehicle classification sensor , a 3D representation of the vehicle or of a part of the vehicle passing the section , which part comprises a portion of the vehicle side ; directing a first camera from a first camera position (P CAM ), in the given coordinate system , onto the section and recording a source 2D image , comprised of pixels (18 i ) representing points in a source 2D image plane , of at least a lower portion of said vehicle side , said camera being calibrated by a mapping between world points in the given coordinate system and image points in said source 2D image plane ; determining , in the given coordinate system , a bounding box circumscribing the 3D representation , a side of the bounding box corresponding to said vehicle side , and the four corner points (29 1 - 29 4 ) of said bounding box side ; identifying , using said mapping, image points of said corner points (29 1 - 29 4 ) in said source 2D image plane as source corner image points (29 1 ' - 29 4 '); defining a destination 2D image plane parallel to the bounding box side in the coordinate system , and the four corner points of a rectangle (27") in the destination 2D image plane as destination corner image points (29 1 " - 29 4 "); calculating a projective transformation between the source corner image points (29 1 ' - 29 4 ') and the destination corner image points (29 1 " - 29 4 "); transforming , using the projective transformation, source 2D image pixels (18 i ) to destination 2D image pixels (33 i ) of a first destination 2D image ; and detecting the wheels of the vehicle using the first destination 2D image by means of an image recognition process. <EOS>