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 (103, 104, 105), 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 (103, 104, 105), 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.