Chapter 5 — Signals and Signs 80 2. Warning Signs The pennant–shaped yellow warning sign emphasizes, rather than replaces, the  rectangular regulatory “DO NOT PASS” sign. The pennant is located on the  left side of the road and points to the beginning of the no-passing zone (solid  yellow line in your lane). A circular sign, with a black cross and the black letters “RR”  on a yellow background, gives advance warning of a railroad  crossing. When you see this sign, slow  down. Stop if necessary to be sure you  can safely clear the crossing. Samples of caution or warning signs At the railroad crossing itself is the  railroad crossing crossbuck sign. The words  “RAILROAD CROSSING” are printed in black  on the white crosspieces. If there are multiple tracks at the  crossing, they are shown on a sign below the crossbuck. You  must stop at a railroad crossing whenever a flagman, signal  or gate indicates an approaching train. You must remain  stopped until the gate lifts or the signal or flagman indicates  that it is safe to proceed. Take the time to check twice in each  direction before crossing a railroad track. black on orange, they warn of conditions  for construction or maintenance  areas. When you see one of these  signs, drive with extra care. One of  the most important caution signs is the  “STOP AHEAD” sign. It is placed far ahead of a  stop sign when the driver’s view of the stop sign is blocked  by a curve or other objects. Diamond-shaped caution or  warning signs that are orange with black messages warn about  construction or maintenance areas. Highway work zones are covered  in more detail in  Chapter 4 — Your Driving. Diamond-shaped signs are also caution or warning signs. They  are normally black on yellow, but when they are 