A door opening mechanism , in particular for public transport vehicles, the mechanism comprising: - a supporting structure ; - a support member designed to carry a leaf of a door ; - coupling means that couple said support member to said supporting structure so that the support member is movable parallel to a horizontal plane, said plane being defined by a first and by a second axis (X, Z) orthogonal to one another; - a guide fixed with respect to said supporting structure , slidingly engaged by said support member and shaped so as to guide said support member along a trajectory on said horizontal plane to open/close said leaf ; - a slider designed to be actuated by an actuator assembly so as to translate with respect to said supporting structure along said first axis (X) between a first end-of-stroke position, corresponding to a closed leaf condition, and a second end-of-stroke position, corresponding to an open leaf condition; and - transmission means (36; 36') that couple said slider to said support member so that a translation of said slider corresponds to a movement of said support member along said trajectory ; said transmission means (36; 36') comprising a first cam (37; 37') carried by a first element defined by one of either said support member and said slider , and a first follower (46; 46') engaging said first cam (37; 37') and carried by a second element defined by the other of either said support member and said slider ; characterised in that said first cam (37; 37') is shaped to prevent said slider from translating towards the second end-of-stroke position, when said slider is arranged in the first end-of-stroke position and said support member receives a force directed parallel to said second axis (Z), wherein said first cam (37; 37') defines a curvilinear path to be followed by said first follower (46; 46') and comprising two extreme points (E, F) and an intermediate point (D) between said extreme points (E, F) defining a dead point position for the first follower (46; 46'); the intermediate point (D) coinciding with the apex of an elbow-shaped section of said curvilinear path or belonging to a straight section of said curvilinear path parallel to said first axis (X). - a supporting structure ; - a support member designed to carry a leaf of a door ; - coupling means that couple said support member to said supporting structure so that the support member is movable parallel to a horizontal plane, said plane being defined by a first and by a second axis (X, Z) orthogonal to one another; - a guide fixed with respect to said supporting structure , slidingly engaged by said support member and shaped so as to guide said support member along a trajectory on said horizontal plane to open/close said leaf ; - a slider designed to be actuated by an actuator assembly so as to translate with respect to said supporting structure along said first axis (X) between a first end-of-stroke position, corresponding to a closed leaf condition, and a second end-of-stroke position, corresponding to an open leaf condition; and - transmission means (36; 36') that couple said slider to said support member so that a translation of said slider corresponds to a movement of said support member along said trajectory ; <EOS>