Multiple Tracks sign
Mounted below the crossbuck, this plaque warns that more than one set of rails crosses the road here, so clearing the first track does not mean the crossing is clear.
Federal designation R15-2 in the MUTCD, the national standard every state signs to. Appears at crossings where freight yards, sidings, or parallel main lines put two or more sets of rails side by side.
How to recognise it
This sign is a square in white, the standard background for a rule you must obey. A round yellow advance warning, then the white crossbuck at the tracks themselves. The crossbuck has the legal force of a yield sign, which surprises a lot of test takers.
What the test wants you to know
The classic mistake it guards against is watching one train pass, then driving across immediately while a second train approaches on another track hidden behind the first. Look and listen in both directions on every track before you cross, not just the one you can see moving.
The sign people confuse it with
Multiple Tracks gets mixed up with Crossbuck more than any other pairing in this category. Put them side by side and the difference is obvious, which is exactly why it is worth doing once rather than meeting them cold in the exam.
Practise it
Reading about a sign is not the same as recognising it in half a second with an examiner watching. Every state road signs test on this site shows the sign and asks you to name it, then shows four faces and asks you to pick the right one.