The traffic control on an intersection consists of permitting and canceling right-of-way to traffic streams. One traffic stream is controlled by one sequence of traffic light indications. These traffic light indications, for one traffic stream, are activated by one module in electronic device (controller). But, one sequence of traffic light indications ca n control more traffic streams, which a re not in conflict. This paper deals with the problem of classifying traffic streams into groups (signal groups) which will be controlled by identical indications of traffic lights. Therefore, the relation of identical indications of traffic lights is defined. This relation is defined over the set of traffic streams on one intersection. The graph of this relation is, also, introduced. A signal group is defined as a clique (in the sense of Berge) of this graph, and the complete set of signal groups is introduced. Computer programs are developed for determination of the collection of complete sets of signal groups, and for determination of all minimal complete sets. In the paper is, also, defined the relation of partial order over the collection of complete sets of signal groups, and the use of this relation in control system design is considered.