Here is a picture of the effect of this on the road.
The footpath was diverted onto the road, with barriers surrounding it. This narrowed the road, so the workers installed the traffic lights. Traffic is so light, though, that most of the time we were left waiting for the light to change but nothing was coming in the opposite direction.
Here is a picture of one of the traffic lights, unplugged by a frustrated resident. No, it wasn't me; I'm law-abiding.
The other one was unplugged, too.
This reinforces my belief that if the space take up by roadworks or whatever is less than that taken up by a parked car, and a car could park where the roadworks are, then you don't need traffic lights any more than you do when someone parks a car there.