A warning notice advises that the traffic lights will operate if a vehicle is travelling faster than the speed limit. The speed limit varies from 20kph to 50 or 60 and overhead traffic lights with eye-level repeaters flash amber in the manner of our railway level-crossing gates. If a vehicle is going too fast, the lights change to red. There is ample warning for following vehicles and presumably the system operates in a similar manner to our speed cameras.
This seems to be a very effective system and is worthy of consideration in the UK.
Incidentally, whilst I drove very little in the big cities, I found the standard of driving rather better than in the UK, apart from the wretched scooters and other two-stroke motorcycles which buzz around, making town centres noisy and fume-laden.