When Civil Engineers use visual aids they use blueprints especially the structural part of Civil Engineering. They communicate the blueprints, by using signs that are specified in a key. Like in the picture above they made a blue print for an intersection, and put semis in it, which are the red things in the pictures, to see if they would be able to fit in the intersection. This was mad by a Engineer for the other engineers on that project so they would know what is going on.