If the subgrade is widened by 50 cm, it is necessary to use scarifiers, graders, bulldozers, scrapers, excavators (with trucks to move soil) and other equipment to widen the subgrade.
"Subgrade is the foundation of track or pavement, and it is a geotechnical structure formed by excavation or filling. The main function of subgrade is to provide necessary conditions for the laying of track or pavement and the operation of train or traffic, to bear the static load, dynamic load and traffic load of track and locomotive or pavement, and to transmit and disperse the load to the depth of foundation.