Originally Posted by Speedo

I have a feeling that the blinking light ==> inability to judge distance is old conventional wisdom. During the mid-70's there was a line of bike lights sold that had an incandescent bulb and a very low blink rate to conserve the battery. That was when I first heard the blinking rear light ==> difficulty judging distance. For that particular line of lights I can believe that it would be true. The blink rate was very low maybe 0.25-0.5 Hz. The cyclist could move a considerable distance in the off interval. If the rider was rocking the bike while he/she rode it could wreak havoc with some observer trying to connect the dots.

For today's LED based flashers The blink rate is much much faster. I'd be very surprised if a modern blinkie resulted in problems with an observer.

As a fine point most LED based headlights that have several intensity levels ARE blinkies. Modulating the blink rate or blink duty is how they achieve the different levels. So at some blink rate it doesn't matter any more; blinking looks like steady.

I checked the Massachusetts laws. There doesn't seem to be any objection to rear blinkies in them.

Speedo