Which statement about using lane 1 of an expressway with 2 lanes in each direction is correct?

1. ①Only passenger cars may use lane 1, and only to overtake.
2. ②Any motor vehicle that is overtaking may use it, and when heavy traffic unavoidably forces speeds below 80 km/h, vehicles may use it even without overtaking.
3. ③Even when the road is clear, you may keep driving in lane 1 without overtaking as long as you keep steadily within the speed limit.
4. ④Trucks may not use lane 1 even when overtaking.