A group relamping model was developed and evaluated by using bulb-replacement records from the Ohio Department of Transportation (ODOT) District 4 as a test case for a limited sensitivity analysis. The relatively easy-to-use Excel spreadsheet computes the costs of group relamping as a function of the relamping interval. The model shows a relatively shallow minimum region at about 10 months, with a minimized annual cost of $38,719 to ODOT District 4 for maintaining the bulbs on its 273 signalized intersections. Results will vary somewhat in other districts or states, but the software can be applied to those cases as well. One of the major tasks involved in using the model is the need to input the individual spot relamping distances, including those from the central maintenance facility to each signal and also the distances of travel to and within clusters of signalized intersections, where each cluster takes 1 day to relamp as a group. The other major difficulty is obtaining a bulb-failure curve to use as input; in this evaluation data for the GE-Real bulb were collected over a 2-year period in ODOT District 4. The intersections also need to be clustered before using the spreadsheet. The software will provide a table of overall traffic-signal maintenance cost on an annual basis as a function of the group relamping interval from 1 to 24 months, from which the group relamping interval with the minimum annual cost can be selected.