People have to make choices when they make trips. The choices may be of destination, of mode of travel, of route or of time. The report describes a simple method of calculating the assignment of trips where travellers are free to choose between alternatives. The method of calculation is called 'SCATA' (Simple Choice Algorithm for Trip Assignment) and is derived from the assumption that travellers vary in their perception of the costs and benefits of the alternatives and choose whichever is best for them. The use of SCATA is illustrated by examples that cover choice of route, of mode and of origin and destination. The theoretical accuracy of SCATA is assessed by comparing the assignments with those predicted by a simulation that is based upon the same fundamental assumptions. It is though that SCATA may be of use in the design of traffic management schemes. For this purpose, the SCATA method of assignment must be joined to a model that predicts trip costs as a function of the assignment. An example is given that shows some of the implications that follow when SCATA is used in this way