предупрежда́ющие зна́ки

warning signs (triangular with orange red border, yellow background and black figures); warn of possibly dangerous conditions or conditions simply to be aware of

запреща́ющие зна́ки

prohibiting signs (round; most use the same colors as warning signs); describe what you CANNOT do

предпи́сывающие зна́ки

limiting signs (blue backgrounds and white figures); describe the only way in which something may be done

informational signs (square

указа́тельные зна́ки

with blue background); describe what may be done, or what facilities are available