Final answer:
If a load is higher than the figure shown on an underpass clearance sign, the driver must find a different route. Ignoring such signs can lead to accidents and infrastructure damage.
Step-by-step explanation:
If your load is higher than the height clearance indicated on an underpass sign, you should find an alternative route. This is important for safety reasons and to prevent damage to both your vehicle and the structure. Proceeding with caution, ignoring the sign, or trying to quickly decrease the height of your load are not safe options.
Road signs are in place to prevent accidents and ensure the safety of all road users, much like weight limits on bridges prevent structural damage.