Quasi-moving block system of train control

A method for increasing the level of protection provided by a communication-based train control system against collisions among of a plurality of trains along a track divided into a series of fixed-block track circuits, including a remote office communicating via a communications network with the trains, each train having an onboard system operating the train in accordance with movement authority limits received from the office via the communications network, said method comprising:

• parsing the route for each train into exclusive movement authorities by the office;
• issuing and subsequently updating a movement authority from the office to each train, thereby granting exclusive authority for each train to move within a movement authority;
• constraining the operation of each train by its onboard system to proceed along the track within its movement authority;
• communicating from each train's onboard system to the office via the communications network to automatically roll up the movement authority for each train, releasing the portion of the movement authority behind the train with a safety margin to allow for any uncertainty in the rear-of-train location as the train proceeds along the track;
• extending by the office the movement authority of a potential subsequent train, allowing it to occupy the released portion of the movement authority of the prior leading train;
• detecting the existence of occupancy by any rail vehicle in each track circuit by applying and detecting an electrical signal to the rails;
• communicating the state of the existence of occupancy by any rail vehicle in each track circuit track circuit to the trains;
• further constraining the operation of each train by its onboard system to protect against a detected unexpected occupancy within the movement authority of each train;
• detecting the existence of broken rail in each track circuit by applying and detecting an electrical signal to the rails;
• communicating the state of the existence of broken rail in each track circuit track circuit to the trains;
• and
• further constraining the operation of each train by its onboard system to protect against a detected broken rail within the movement authority of each train.