Final answer:
The sign advises drivers that the shoulder of the road can only be used for emergencies.
Step-by-step explanation:
The sign advises drivers about the shoulder of the road by indicating that it can only be used by vehicles in case of an applicable emergency. This means that the shoulder of the road should not be used for purposes such as parking or stopping unless there is an emergency situation. The sign serves as a reminder to drivers to keep the shoulder clear and accessible for emergency vehicles or for drivers in need of assistance.