Method of responding to resource requests in a trunked communication system without call-handoff

A radio communication system (200) having a communication site (203) provides communication services to a coverage area (201) surrounding the communication site (203). A plurality of service resources are allocated (318) among a plurality of communication units (205) located within the coverage area (201). A method of responding to a service request transmitted from a requesting communication unit includes the steps of determining (310) a nominal service duration, and estimating (312) an available site time value. A completion probability value can then be calculated (403) using these parameters. The completetion probability value is then used to determine (405-413) whether or not to allocate, to the requesting communication unit, a service resource corresponding to the requested service.