Replacement policies for traffic control signals

We discuss the application of two types of maintenance policy for multi-component systems to find good schedules for the replacement of lightbulbs in traffic control systems. Both types are based on the fact that in general many lamps function close together, implying that economies of scale can be obtained by combining replacements. In the first policy type, corrective and preventive maintenance are strictly separated, and the economies of scale are achieved by combining preventive maintenance actions on various classes of bulb (indirect class grouping policies). The second policy type (opportunity based replacement) is based on the principle that failures of individual bulbs can be considered as opportunities for preventive maintenance on other (classes of) bulbs, thus saving fixed costs. As a case study we present the maintenance of the traffic control system on a major road crossing in Amsterdam.