What is the meaning of a yellow diamond sign depicting a truck on a descending triangular slope with percentage numbers (e.g. '8%')?

1. Truck sales lot ahead with an 8% discount
2. Warning: steep downhill grade ahead (Pendiente pronunciada / Bajada peligrosa), requiring drivers to reduce speed and engage low gear and engine retarders before the descent
3. Mandatory truck weigh station
4. Eight percent increase in statutory speed limit