26: Shark teeth
Problem: Ask yourself this question: "at an intersection, do I always know who has a right of way?" The answer to this question is usually "no". Statistics confirm this. A very high number of traffic accidents happens at intersections without traffic lights.
The solution is simple: "shark teeth", drawn on the road as you can see on picture. Are the shark teeth pointed towards you? You have to give priority to crossing traffic. Are the shark teeth in line? You have a right of way.
Simple, cheap and always very clear. Many countries already use them.
An additional benefit is that all side roads will be clearly visible from the main road; avoiding even more accidents.