What action must dispatchers take in response to reports of a bridge strike on a critical bridge?

When dispatchers receive reports of a bridge strike on a critical bridge, the primary action they must take is to hold all trains clear of the bridge. This is crucial because the structural integrity of the bridge may be compromised after an impact, posing a significant safety risk to trains and their passengers. Holding trains clear ensures that no additional load is placed on the bridge until it has been properly assessed by qualified personnel.

This action prioritizes safety and allows for a thorough investigation of the bridge's condition before any trains can safely proceed or the bridge can be reopened for use. Other responses, such as continuing operations as normal or allowing only emergency vehicles to cross, do not adequately address the immediate safety concerns presented by a potential hazard on the bridge. Redirecting trains might be necessary as a follow-up action, but it cannot replace the critical initial measure of ensuring that no trains approach the potentially dangerous area.