Do Not Stop On Tracks sign
Never stop your vehicle on or near the rails, even if traffic ahead is backed up. Wait until the space beyond the crossing is clearly open before you enter it.
Federal designation R8-8 in the MUTCD, the national standard every state signs to. Found near signalized intersections or driveways positioned close enough to the tracks that a red light could otherwise trap a car across them.
How to recognise it
This sign is a tall rectangle 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 scenario tests almost always describe a backed up intersection right next to a crossing and ask what you should do before proceeding. The correct answer is to hold back at the tracks until you can see open space on the far side, not to inch forward and hope traffic clears in time.
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.
Railroad Crossing Ahead
Crossbuck
Exempt Crossing
Multiple Tracks
Look