It's harder than it looks. I see two possible interpretations of your proposal: a) Not change the worker's checklist. That would mean they should deviate from

It's harder than it looks. I see two possible interpretations of your proposal: a) Not change the worker's checklist. That would mean they should deviate from the list, creating a dangerous precedent. b) Adding another rule to the worker's checklist. Great, now they need to check this for every single light they are working on, which means more work (is that really cheaper than the bulbs even if it's only a few seconds per light?) and more possibilities of doing mistakes. Not to mention that the traffic light probably refuses to turn on when not all lights are installed. That means the software needs to be changed. Yet another possibility to introduce fatal mistakes at other intersections. I prefer paying for a bulb every now and then to putting human lives at risk. Note that changing something for this intersection means changing things for all intersections, including high-traffic complex ones.