At rail crossings with a standard red-and-white stop sign, when can drivers proceed?

At rail crossings marked with a standard red-and-white stop sign, drivers must stop and then check for any approaching trains before proceeding. The key here is that the sign indicates they need to assess the situation for any potential hazards, particularly the presence of a train.

Determining that no train is approaching means that the driver has taken the essential step of stopping at the crossing and ensuring it is safe to move forward. This is crucial for safety, as trains can come at high speeds and can be difficult to hear or see in certain conditions.

The other options focus on conditions that do not align with the requirements set by traffic regulations at rail crossings. For instance, proceeding when they see the train approaching would obviously be dangerous, and checking for pedestrians—while always a good practice—does not address the main concern at a rail crossing. Finally, waiting for a light to turn green is applicable to traffic signals but does not pertain to the rules governing rail crossings. Thus, understanding the significance of ensuring the track is clear of trains before proceeding is paramount for safety at these crossings.