Virtual Block Signaling

Virtual Block Signaling ​is a safety-critical SIL 4, CENELEC-compliant product that provides the safety-critical delivery of Mandatory Directives (movement authorities and restrictions) to trains in electronic-only mode (elimination of read and repeat).

In addition, Virtual Block Signaling ​ensures vital overlap protection of electronic and verbal authorities in Track Warrant Control (TWC) operation. Train-control solutions based on IVOC require minimal wayside components installation, reducing the CAPEX and OPEX cost for signaling of new railway lines or existing ones to be rehabilitated.

Virtual Block Signaling ​provides the following key functions:

• Electronic-only delivery of movement authorities and restrictions to trains in electronic-only mode, providing a paperless cab
• Restriction mapping to movement authorities for trains in both CTC and TWC territories
• Movement authority overlap validation
• Will permit overlaps for contingent authorities when marked as contingent
• Authority-verbiage validation to ensure verbal authorities known to the crew is what IVOC is protecting
• Alternate protection to ensure accidental removal of a movement authority leaving the entity unprotected
• Enter Main Track (EMT) overlap protection for hand-thrown switches
• Pass Signal at Stop (PSS) overlap protection if another vehicle is already authorized for that section of track
• Crew-initiated rollup and release to allow crew to rollup movement authority in conjunction with TMC to allow IVOC or dispatcher to authorize next train for that section of track
• PIN protection for verbal authorities giving ownership of movement authority to crew as to when it can be released
• Improved train location reporting in dark territory
• Improved authority-violation reporting by reducing bandwidth, only sending report to CAD and violated train if train violation overlaps that train’s movement authority

Future functionality:

• Remote control of switches in dark territory
• Unmonitored switch status determined by handling reports and onboard traversal reporting
• Automatic rollup of movement authority with inclusion of GPS-enabled End of Train (EOT) device
• Dynamic authority where movement authority will be sent to a train as the leading train releases track
• Restricted speed collision avoidance in CTC territory