Under Article 43 of the PRC Road Traffic Safety Law, in which of the following situations is overtaking strictly PROHIBITED (不得超车)?

1. On a straight, dry expressway with visibility over 500 meters
2. When driving on a multi-lane urban elevated road with broken white lane lines
3. When traveling behind a vehicle moving at 20 km/h in a rural area with broken yellow lines
4. When the vehicle ahead is turning left, making a U-turn, or overtaking another vehicle; or in railway crossings, sharp curves, narrow bridges, tunnels, or pedestrian crossings