Abstract
A specification of a part of an existing system for traffic regulation at signalized intersections is given. The system that is chosen as subject to specification is developed by the Dutch company Nederland Haarlem. The specification, in PSF, centres on the algorithm performing the regulation, which is, in the authors' view, the most interesting part. The specifications given is data-oriented, i.e., there is not much emphasis on processes. Although time plays an important role in the regulation process, this is not an obstacle for specification. (A)