What must occur before implementing DCS rules over ABS rules when a signal system failure happens?

In the context of implementing DCS (Dispatcher Controlled System) rules over ABS (Automatic Block Signal) rules during a signal system failure, it is crucial that safety inspections are conducted to ensure the integrity of the track and associated infrastructure.

The requirement for a test train to inspect the track and catenary before switching to DCS rules ensures that any potential hazards are identified and mitigated. This is because DCS rules place more responsibility on the dispatcher and rely on their control of train movements in circumstances where signals are not operating correctly. A test train verifies that the route is clear, that the track and catenary are safe for use, and that any issues are addressed before allowing train operations under a potentially less secure signal system framework.

While checking signals for functionality, performing a full system reset, or training operators are all important components of operational safety, they do not specifically address the immediate need for verifying the physical infrastructure before moving to a less automatic system like DCS, which could lead to safety critical issues if the conditions are not right. Hence, the conduct of a test train inspection is vital and precedes the implementation of DCS rules over ABS rules in such scenarios.