Tread pattern motif for a tread

A heavy-vehicle tire, the tread of which comprises a directional tread pattern formed by a plurality of grooves of generally circumferential orientation and a plurality of transverse grooves, said grooves defining a plurality of tread pattern motifs, each motif having

• a contact face, two lateral faces, a leading face and a trailing face, the leading and trailing faces intersecting the contact face along a leading ridge and a trailing ridge, the leading ridge corresponding to that ridge of the tread pattern block which first comes into contact with the ground,
• the leading face being oriented such that the angle α measured in the motif between the leading face and the contact face is greater than 90°, the trailing face having a part which is undercut relative to the running face, wherein
• the trailing face is formed of two parts which divide said trailing face into a lower part and an upper part in the direction of the height of the motif, the upper part extending from the running face of said motif, the lower part extending the upper part towards the inside of the tread, the lower part representing between 20% and 80% of the total height of the trailing face, the upper part of the trailing face being inclined at an angle β less than 90° relative to the contact face so as to be undercut, whereas the lower face, which is oriented so as to form an angle δ greater than 90° with the same contact face, is provided with a plurality of recesses which extend within the block at least as far as a plane perpendicular to the contact face and passing through the radially innermost point of the lower part of the trailing face, the total of the areas of said recesses on the lower part being between 30% and 70% of the total area of said lower part.