a heavy duty pneumatic radial tire exhibiting less railway wear is disclosed . this tire has a tread pattern formed in a tread divided into a plurality of circumferential ribs by at least two zigzag grooves . each of these zigzag grooves has a width , amplitude and pitch of 4 . 5 to 7 . 5 %, 0 . 5 to 2 . 0 % and 2 . 0 to 7 . 0 %, respectively , based on a width of the tread .