Vehicles must not be driven to the left side of the roadway when within __________ feet of a bridge, viaduct, or tunnel.

The correct answer is 100 feet, which is important for ensuring safety when approaching structures such as bridges, viaducts, and tunnels. This regulation is designed to maintain proper visibility and lane discipline in areas where there may be limited space or increased danger due to the proximity of these structures. When vehicles are too close to these areas, it can be difficult for drivers to see oncoming traffic and adequately gauge whether there is sufficient space to maneuver.

By prohibiting vehicles from driving on the left side of the roadway within this distance, the law helps to guide drivers to remain in their designated lanes, reducing the risk of collisions and enhancing overall traffic flow in potentially hazardous zones. Understanding this regulation is crucial for drivers to navigate safely and comply with road rules effectively.