If you mean a diamond on the lane, that means that that lane is for BICYCLISTS ONLY, if you mean as a shape of a sign such as a "slippery when wet" sign, that usually tells you important things. I looked it up in my "Virginia Driver's Manual" and it says a diamond shaped sign is a warning sign.
A diamond shaped sign is usually a warning sign.
to warn of a possible danger ahead.
The UK Highway Code does not show diamond shaped traffic signs because they are not authorised as legal road signs in the UK.
warning sign...warning you of road hazards or upcoming objects. There is diamond type symbol found on the seals found from pre-historic Harappan Civilization in South Asia. the decrypted text shows it as a sign of currency.
bhenchod
warningA merging traffic sign an example of a warning.warning signyellow diamond
warningA merging traffic sign an example of a warning.warning signyellow diamond
Warning sign of possible danger ahead
A sign that you will never get laid.
That traffic sign is called a "crossbuck".
It is found in VERY few areas and it means a change in the road from a 4 lane to a 2 lane road.
Usually are yellow and diamond-shaped, with black lettering or symbols.
railroad