The multiple-aspect signalling scheme, or MAS, was the two-stage introduction of multiple-aspect light signalling in the Sheffield area, which began in 1971. The scheme began with the reduction of the quadruple track between Sheffield Midland and Dore & Totley and the simplification of the "up" entrance to Sheffield Midland. The reduction in track was completed by January 1972 with the closure of Dore West and Dore South signal boxes. The dive under built in 1900 was taken out of use from 25 June 1972. There, the track was reduced from four to three and to two between Heeley and Dore & Totley. A passing loop was kept between Heeley and Millhouses.