How does the Congolese Highway Code fix the distance at which a danger warning sign is placed ahead of the hazard?

1. At whatever distance makes the sign most effective by day and by night, given road and traffic conditions, the usual speed of vehicles, and how far away the sign is visible
2. Always exactly 150 metres before the hazard, on every class of road
3. Always exactly 50 metres before the hazard, on every class of road
4. Always level with the hazard itself, so the driver sees the sign and the danger together