A ramp structure (200, 400), the ramp structure (200, 400) comprising: first and second ramp kerbs, each ramp kerb (204a, 204b) comprising a first longitudinally extending channel open at an inner transverse edge of the ramp kerb (204a, 204b) and a second longitudinally extending channel open at the inner transverse edge of the ramp kerb (204a, 204b), wherein said first and second longitudinally extending channels are vertically spaced; a ramp surface (202, 410a, 410b) having transverse edges spaced by an uppermost lateral edge and a lowermost lateral edge, a first of the transverse edges of the ramp surface (202, 410a, 410b) being received in the first longitudinally extending channel of the first ramp kerb, and a second of the transverse edges of the ramp surface (202, 410a, 410b) being received in the first longitudinally extending channel of the second ramp kerb; and a ramp lip extension (300, 412) comprising a lip surface having transverse edges spaced by an uppermost lateral end and a lowermost lateral end, and an attachment portion, said attachment portion comprising a downwardly depending skirt depending from the uppermost lateral end of the lip surface and at least one projection projecting from said skirt away from said lip surface, wherein said at least one projection is vertically spaced below said uppermost lateral end of the lip surface by said skirt, the at least one projection of the ramp lip extension (300, 412) being received in the second longitudinally extending channels of the first and second ramp kerbs, such that the uppermost lateral end of the lip surface is in abutment with the lowermost lateral end of the ramp surface (202, 410a, 410b). first and second ramp kerbs, each ramp kerb (204a, 204b) comprising a first longitudinally extending channel open at an inner transverse edge of the ramp kerb (204a, 204b) and a second longitudinally extending channel open at the inner transverse edge of the ramp kerb (204a, 204b), wherein said first and second longitudinally extending channels are vertically spaced; a ramp surface (202, 410a, 410b) having transverse edges spaced by an uppermost lateral edge and a lowermost lateral edge, a first of the transverse edges of the ramp surface (202, 410a, 410b) being received in the first longitudinally extending channel of the first ramp kerb, and a second of the transverse edges of the ramp surface (202, 410a, 410b) being received in the first longitudinally extending channel of the second ramp kerb; and a ramp lip extension (300, 412) comprising a lip surface having transverse edges spaced by an uppermost lateral end and a lowermost lateral end, and an attachment portion, said attachment portion comprising a downwardly depending skirt depending from the uppermost lateral end of the lip surface and at least one projection projecting from said skirt away from said lip surface, wherein said at least one projection is vertically spaced below said uppermost lateral end of the lip surface by said skirt, the at least one projection of the ramp lip extension (300, 412) being received in the second longitudinally extending channels of the first and second ramp kerbs, such that the uppermost lateral end of the lip surface is in abutment with the lowermost lateral end of the ramp surface (202, 410a, 410b).