Which statement describes the passing rule when the lead vehicle is having mechanical difficulties?

• A. Other vehicles may pass if the lead vehicle is having mechanical difficulties
• B. No passing allowed under any circumstance
• C. Only with supervisor approval
• D. Other vehicles may pass if the path is clear

Answer: (D)

When the lead vehicle is having mechanical difficulties, passing is allowed only if the path is clear. This keeps the operation moving and safe: the following units may proceed past the struggling lead unit as long as there’s a safe, unobstructed lane and no opposing traffic or other hazards in the passing area. Signals, situational awareness, and coordination with the crew are still important, but the primary condition is that the roadway segment you intend to use is free of danger so passing won't create new risks.

This rule avoids unnecessary delays that would come from requiring supervisor approval or from declaring no passing at all, and it avoids vague criteria by specifically tying passing to the actual safety condition of the path being clear.