Block System, a method of working trains on a railway to ensure that a definite distance exists between consecutive trains. The line is divided into sections, and no train is allowed to enter on any single section till the train in front has left it. The signals are worked by telegraph at each end of each section. On Electric Railways, worked by conductor methods, an automatic block system is possible. The existence of a train on one section of the line may be made to prevent any motive power being transmitted to another trap on the same section, and so may render any nearer approach impossible till the first has passed off.