On a steep downgrade, a conductor notices the train is accelerating beyond the target speed despite maximum dynamic braking and air brake application. What is the conductor's responsibility at this point?

1. Increase radio contact frequency and document the event
2. Communicate with the engineer, escalate to emergency brake if speed cannot be controlled, and notify the dispatcher
3. Remind the engineer to apply the handbrake on the locomotive
4. Monitor speed only; the engineer has sole responsibility for braking