Quasi-moving block system of train control

Abstract

A system of train control uses a quasi-moving block methodology for controlling operation of a plurality of trains from a remote office. The office parses the route information for each train into non-overlapping movement authorities that are issued via a communications network. As each train proceeds, it communicates with the office to automatically roll up its movement authority and release the portion of the movement authority behind the train. The office then extends the movement authority of the subsequent train to reflect the released portion of the movement authority of the leading train. The track can be divided into a series of track circuits to enable detection of broken rail or unexpected occupancy. The office segment can then control operation of trains accordingly if broken rail or unexpected occupancy is detected in the train's movement authority.

We claim: 
     
         1 . A method for increasing the level of protection provided by a communication-based train control system against collisions among a plurality of trains along a track divided into a series of fixed-block track circuits, said method comprising:
 parsing the route for each train into exclusive movement authorities;   issuing and subsequently updating a movement authority to each train, thereby granting exclusive authority for each train to move within a movement authority;   constraining the operation of each train to proceed along the track within its movement authority;   automatically rolling up the movement authority to release 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 the movement authority of a potential subsequent train, allowing it to occupy the released portion of the movement authority of the prior 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 existence of occupancy by any rail vehicle in each track circuit to the trains;   further constraining the operation of each train 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 existence of broken rail in each track circuit to the trains; and   further constraining the operation of each train to protect against a detected broken rail within the movement authority of each train.   
     
     
         2 . The method of  claim 1  further comprising enabling a following train to proceed at up to maximum authorized speed into an occupied track circuit block, if the track circuit has the ability to detect a broken rail within an occupied block, upon receiving information that: (a) no broken rails have been detected in the occupied track circuit block between the entry part of the track circuit block in the direction of travel and the rear-of-train location of the leading train; and (b) the leading train that is occupying that track circuit block has a functioning rear-of-train location determination or train integrity determination system. 
     
     
         3 . The method of  claim 1  wherein the step of rolling up of movement authorities is repeated over time at a frequency based at least in part on at least one of: (a) the distance between the subsequent train and the rear of the leading train; (b) elapsed time; (c) elapsed distance; and (d) the train location relative to predetermined points along the track. 
     
     
         4 . The method of  claim 1  wherein each movement authority rollup location is based on a rear-of-train location determination system that reports absolute rear-of-train location to the front of the train. 
     
     
         5 . The method of  claim 4  wherein a movement authority rollup location is determined at least in part from the reported distance traveled by the rear of the train since the rear-of-train location was last reported. 
     
     
         6 . The method of  claim 4  wherein a movement authority rollup location is determined at least in part from the reported average rear-of-train speed since the rear-of-train location was last reported. 
     
     
         7 . The method of  claim 2  wherein an onboard system on each train applies a restriction when an occupancy is detected within a block by the track circuit for that block and the occupancy is not expected because the train's exclusive electronic movement authority extends through the entire block. 
     
     
         8 . The method of  claim 2  wherein a speed restriction is applied in areas with a potential rail vehicle rollout, comprising:
 providing the onboard track database having information regarding whether there is a derail or rollout detector installed at each switch; 
 the onboard system checking the track database in advance of the predicted braking distance ahead of each switch in a block with an occupancy ahead, and if there is not a derail or detector installed at the switch, the onboard displaying and enforcing a speed restriction at that switch rather than allowing operation at maximum authorized speed; 
 if the train enters the block before the occupancy ahead clears the block, the onboard system continuing to enforce a speed restriction at each hand-throw switch ahead in that block that lacks a derail or rollout detector. 
 
     
     
         9 . The method of  claim 2  wherein a broken rail location is estimated by identifying the rear-of-train position at the time when the track circuit detects the rail break. 
     
     
         10 . The method of  claim 1  wherein the system sets the boundary between parsed movement authorities for joint occupants of a bidirectional movement authority based on location destinations requested by a joint occupant. 
     
     
         11 . The method of  claim 1  wherein the boundary between parsed movement authorities for joint occupants of a bidirectional movement authority is automatically set based on at least one of: (a) updated reports of location; (b) train speeds; and (c) braking distance from at least one of the joint occupants. 
     
     
         12 . The method of  claim 1 , wherein movement authorities are provided to each train in a format compatible with the train's level of onboard system functionality and interface protocol as known by the office. 
     
     
         13 . The method of  claim 1 , where the rate of automatic movement authority rollup by each train is assigned by an off-board system based on changing conditions. 
     
     
         14 . 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.