Where:
On any road, especially in mountainous or hilly areas, where the route passes through a tunnel or underpass.
These tunnels are often built through hills or mountains to allow safe and direct passage for vehicles.

Purpose:
To warn that a tunnel is ahead so that you can prepare for changes in driving conditions.
Inside a tunnel, lighting is reduced, road space may be narrower, and visibility can be limited due to shadows, curves, or oncoming headlights.
The sign alerts drivers to adjust their speed and be cautious before entering.

Action:
Reduce your speed as you approach the tunnel entrance.
Switch on your headlights to improve visibility and make your vehicle more visible to others.
Remove sunglasses before entering, as the lighting inside is usually dimmer.
Avoid overtaking, harsh braking, or sudden steering movements.
Maintain a safe following distance and stay in your lane throughout the tunnel.
Drive carefully and remain alert until you have safely exited the tunnel.