I work at Visionect and have helped develop the eink platform for these signs. They can be changed with whichever frequency is required, more frequently or less so (once a day etc). And while the technology is one thing, as mentioned before, good design is the one that can eliminate any confusion that people may have on how long the restrictions may last. There's more info on our website if you're interested: http://v.visionect.com/sydney_epaper_road_signs