Although LinSig started life as a design and modelling tool for individual traffic signal junctions it has been extended and improved many times to now be a fully fledged modelling tool for networks of signals as well as retaining the ability to model single junctions. A central idea behind LinSig is that it models traffic signal junctions in a similar way to how a real traffic signal controller actually works. This means that LinSig takes account of the features and constraints of the controlling equipment, thereby ensuring that all modelling accurately reflects how existing junctions work, and how any design proposals would operate if implemented.