A supervisor (of a continuous-time or hybrid system) is a controller in charge of modifying the input assigned by a user or set of users to a system, in order to enforce a given specification. This paper describes conditions under which multiple supervisors, designed to enforce different specifications, can be composed to obtain a supervisor enforcing the union of those specifications. As an application, we propose the composition of two supervisors, one enforcing collision avoidance of a large multiagent system, the other enforcing a second property, called sparsity, that allows efficient computation of the collision avoidance conditions.