Which signs indicate a railroad crossing?

The correct answer identifies 'X' shaped signs as indicators of a railroad crossing. These signs are specifically designed to alert drivers to the presence of a railroad track ahead, signaling that they need to approach with caution. The 'X' shape is universally recognized as a warning for crossing hazards, and these signs typically feature the words "Railroad Crossing."

In contrast, circular yellow signs are indeed used for warning purposes but are more commonly associated with caution in various situations, such as indicating curves or pedestrian crossing areas, rather than specifically signaling a railroad crossing. Square green signs typically provide guidance or direction, such as indicating parking areas or showing general information about destinations, and rectangular blue signs usually offer information related to services available at the exit or along a road.

This divergence in signage shapes and colors helps in ensuring that drivers can quickly and accurately identify the risks associated with railroad crossings, contributing to road safety.