What type of risk can a bollard protect against?

Bollards protect against vehicle collisions, unauthorized access, and security threats like vehicular terrorism. They also safeguard pedestrians, guide traffic, and prevent accidental intrusions, making them crucial for both security and traffic management.
How do bollards go up and down?

Automatic bollards use hydraulic, pneumatic, or electric systems to raise and lower. Hydraulic uses fluid, pneumatic relies on compressed air, and electric uses motors. Manual bollards require physical lifting, with semi-automatic versions assisted by springs.