Communications-based signaling: advanced capability for mainline railroads

Train control has three major functions: (1) protection; (2) operation; and (3) supervision. These functions of train control have been (and still are) implemented both manually and automatically at various railways. The first of these functions, train protection, prevents trains from traveling onto sections of track where they could collide with another train or derail due to switch positions. It also prevents trains from exceeding the safe operating speed, as determined by the vehicle type and track geometry (curves and gradients). The second function, train operation, involves the guidance of a single train in motion and at rest, when it is operating within the train protection function. Finally, train supervision involves guiding and recording the progress of multiple trains in an effort to provide economies to, or assign priorities throughout, the overall railway.