What action must be taken first when investigating an accident involving a bus?

The first action to take when investigating an accident involving a bus is to get a verbal briefing from the operator. This step is crucial because the operator can provide immediate insights into the events leading up to the accident. Their account can contain vital information about the conditions, other vehicles involved, and the behavior of passengers, which is essential for a thorough investigation. Understanding the operator's perspective helps establish a clear narrative of what occurred and can inform subsequent actions such as securing the scene, conducting visual inspections, or documenting the evidence.

Securing the bus, while essential, typically follows gathering initial information from the operator, as you must understand what happened before moving to secure the site. Visual inspections and marking locations are also important, but those steps are informed by the context provided by the operator's briefing. Therefore, prioritizing the operator's account ensures that subsequent actions are based on a thorough understanding of the incident.