When may you drive on the shoulder of a roadway?

Answer: D — When directed to do so by a peace officer

Driving on the shoulder of a roadway should only be done when directed to do so by a peace officer. This is typically done in emergency situations, such as directing traffic around an accident or road closure. Option A is incorrect because driving on the shoulder when the roadway is blocked can be dangerous and can impede emergency vehicles that need access to the blocked area. Option B is incorrect because driving on the shoulder to avoid slow-moving traffic is not allowed and can create an unsafe situation for both drivers and pedestrians. Option C is incorrect because turning left from the shoulder of a roadway is not a legal or safe maneuver. Turning should be done from designated turning lanes or at intersections. Overall, it is important to remember that driving on the shoulder of a roadway is only allowed when directed to do so by a peace officer and should not be used as a way to bypass traffic or obstacles.