Line

The Railroad Crossing sign uses lines to share a messages. The two parts of the sign cross each other and the message being shared is that a railroad is crossing a path.
Color

Gambino’s Pizza sign uses the colors green, white, and red. These are the colors that are on Italy’s flag. So, this design uses color to share a message on what kind of food is served at the restaurant.
Texture

This sign is made out of brick and literally has texture. It is three dimensional and has the wording, plane, and pilot sculpted out. I think it’s a unique sign that is effective.
Shape

This stop sign is an octagon. I’ve never seen a stop sign that isn’t this shape. Also, I’ve never seen other road signs use an octagon shape. For this reason, I think the shape is very effective.