What must a driver do when approaching a railroad crossing where the barriers are open?

The correct response emphasizes the importance of safety and vigilance when approaching railroad crossings, even when the barriers are open. Approaching at a moderate speed allows the driver to maintain better control of the vehicle and prepare to react to any unforeseen circumstances. Observing the tracks to the right and left is crucial because trains can come from either direction, and there may not be warning signs or signals indicating their approach. Being cautious in this manner significantly decreases the risk of accidents and enhances overall safety at railway crossings.

In contrast, proceeding without slowing down disregards the potential dangers present, as it could lead to missing a train that may be approaching rapidly. Coming to a complete stop and then looking around is overly cautious and could create unnecessary delays, whereas accelerating to cross quickly is dangerous behavior that increases the chances of a collision with a train. Hence, the correct answer emphasizes a balanced approach to ensuring safety while navigating through railroad crossings.