To build a "correct" implementation from a model of a concurrent real-time system, it is important to understand the relation between the properties of the model and of its corresponding implementation. In this paper, the behaviour of a system is described with timed action sequences. Based on a notion of distance that expresses the observable property preservation between timed action sequences, we show that a stronger observable property preservation between model and implementation is obtained when urgency on the execution of observable actions is imposed over the execution of unobservable ones. Furthermore, we present a model synthesis approach and, by means of a case study, we show how it can be applied in the synthesis of real-time systems.