When may a bus be driven with an emergency-exit door or window open?
Correct answer: D – Never
The District of Columbia CDL manual states that a bus must never be driven with an emergency-exit door or window open. Open emergency exits should be closed during the exterior and interior inspection. Emergency-exit signs, handles, and any required warning lights must also be in proper condition.
Source: DC DMV Commercial Driver License Manual — §§ 4.1.2–4.1.3, “Access Doors and Panels” and “Bus Interior”

