part time lights

I'm sure I've blogged about this before but why o why are traffic lights not part-time by default and only extended to 24 hours as required?
All you need is a reflective badge on the traffic signal so you can see that you are approaching a junction but switch the lights off to reduce power and the annoyance of waiting at so many red lights for no reason. It is a no-brainer to me. If someone jumps them and crashes, its no different than if you pulled out of a side-road with no traffic lights and crashed.
If you really needed to, you set them all to orange so it is clearer but I like the idea of switching them off altogether.
Part time signals do exist, although mostly on roundabouts and slip-roads, so it is obviously permissible and possible.
Come on someone, do it. Lead the way. Be leaders not followers. Show some unction. Think outside the box. Save tons of money and tons of hassle.