Street signs is another thing that is consistently designed. Imagine if street signs had a different picture but the same meaning wherever you went, which would just be a recipe for disaster. In street designs common colours are used e.g. red, yellow and white being the main colours as these catch peoples attention. Also keeping in with the common colour theme a stop sign is red but on a traffic light, when that shines read it also means stop, this is consistent design used in a functional and internal manner.