1. The problem statement, all variables and given/known data (a) Draw a graph with the vertices corresponding to the traffic flows and the arcs corresponding to flows that can occur at the same time. (Called a compatibility graph) (b) Show that finding subgraphs of the compatibility graph which are the biggest possible complete graphs, determines the optimum traffic light phasing needed and hence determine that phasing. 2. Relevant equations 3. The attempt at a solution The problem is, I don't even understand what the question wants from me. I'm not asking for the solutions for both the question, (in fact there is a third part of the question which I am sure I can answer if someone could help me with question (a) and (b)) instead, I really need help on understanding the question itself and a rough idea on how to solve the problem. By the way, can anyone tell me what's actually a 'compatibility graph'?