An article written by Noboru KUBO , Tatsuya KOBAYASHI , Sou KITAJIMA  and Toshihiro ARAI on the subject of active safety. The article, entitled "LED Traffic Signals on Motion Pictures of Drive Data Recorders" pointed out a possible issue with LED traffic signals: 

"LED (light emitting diode) traffic signals that have recently been replacing the current bulb signals in Japan have several advantages such as longer life, less power consumption, and no pseudo-emissions due to reflections, etc. The authors, however, found that scenes with LED signals turned off for seconds were sometimes captured in the motion pictures taken by drivedata recorders (DDR's) because the flicker cycle of the LED lamps synchronizes with the frame rate of DDR's. The phenomenon can make it impossible for an analyzer of traffic accidents to determine the state of traffic signals. This article presents the cause of the phenomenon and some possible solutions. The authors hope that all the manufacturers and handlers of DDR's will pay attention to the problem."

As we become more and more safety conscious, I realise that there's often a compromise needed. As an example, I take the case of Xenon bulbs used in car headlights. The light is bright, strong, well directed and much more efficient than that of the traditional headlight. As a pedestrian I'm glad to know that drivers will spot me rapidly. However, as a driver when I'm confronted with a pair of these modern efficient safety elements, I know that for the following seconds, as my eyes readjust, I'll be temporarily blinded, confronted as I am with a pair of black dots caused by the high contrast in luminance.

So I ask the question, is it better to be seen or to see? And, of course, there's no correct answer...

You could easily resolve the issue of the DDRs by having dual circuits, so that not all of the LEDS are off at the same time.  So long as the frequency is higher than the persistence of vision it will look the same.   There was a novel idea with headlamps that moving into the ultraviolet region and producing flourescing road markings would reduce the dazzle whilst also improving visibility of the road signs.  I think they got the idea from herds of moose in Scandinavia, who happen to fluoresce.