Another hypothesis about a technology that might improve traffic safety (h/t Mike on Traffic) Can't Cross A Virtual Wall A holographic projection of pedestrians in a crosswalk, so they are more obvious to drivers.
One can think of many issues, among them driver expectations being reset. I.e. if this is one place, fine, it may alert drivers, but if this is "almost" everywhere, it might create problems where it is not. And what if it fails where expected?