Which of the following is not a passive warning for railroad crossings?

Railroad gates are considered active warning devices because they actively signal the presence of a train approaching a crossing. When activated by a train, these gates lower to block vehicles and pedestrians from crossing the tracks, which provides a direct and clear indication of danger.

In contrast, passive warnings rely on visual cues to alert drivers and pedestrians to the potential presence of trains, without actively controlling access. For example, a stop line with a cross buck is a passive warning as it indicates where to stop and signifies a railroad crossing. Similarly, a yellow circular advance warning sign and a diamond-shaped parallel track sign serve to inform road users ahead of time that they are approaching a railroad crossing.

Understanding the distinction between active and passive warning devices is crucial for safe driving, especially in areas where railroads intersect with roadways.