Originally Posted by NewbieRunner

I've done some google searches and it seems to be true. (Can't find anything in English so far...)

Speed cameras (called "Orbis" in Japan) are only triggered when the speed of a vehicle exceeds the limit by more than 30km/h on ordinary roads and 40km/h on expressways. Very powerful infrared flashes are used at night and also sometimes during the day as a warning to drivers. Apparently pictures are surprising clear but if a photograph of the driver is not good enough they don't bother to send a summon as it would be difficult to prove who the driver was.