Here's an interesting point. Very rapidly flashing lights, like dimmed LED car tail lights, show up on the human retina as dashed lines after a visual saccade.
I wonder if visibility could be helped by leaving some flashing in the tailights when they're full-bright : when the brake-light mode is activated.
(I mean LEDs that are dimmed by flashing them on and off at a rate faster than persistence of vision.)
Another visual thing. This is a pet peeve. Emergency vehicles use flashing BLUE lights. That's perceptually stupid. For one thing, human eyes, opened up (wide pupils, typical at night) do a better job of focusing longer wavelength light. This has two consequences:
-- it's slightly harder to locate the source of the light because it isn't as neatly focused on the retina.
-- the poorly focused blue light splatters all over the retina, desensitizing the rods of peripheral vision and spoiling dark adaption right when it's needed - entering into a zone where an emergency vehicle is active.
Secondly, red light-- deep red light -- selectively desensitizes the cones in the fovea, leaving the rods in peripheral vision sensitized.
Conclusion: orange light would be a much better choice than blue for cop car flashing lights. It would focus better, preserve dark adaptation better, and preserve nighttime peripheral vision better.
I think if the whole system was redesigned from scratch a lot of things would be different.
Why on earth do we use red and green for signalling stop/go when a statistically significant number of men (plus a few women) have difficulty seeing those colours?
It seems that once you get past a certain level of adoption, it becomes impossible to change even an obviously sub-optimal design.
Blinking lights while noticeable, especially at a distance, it can be difficult to judge closing speed. As a driver, I find it difficult to judge closing speed when the cyclist is oncoming.
The rules for brevets (long distance cycling events) is that both front and rear lamps must be steady state. Additional blinking lights are acceptable. Essentially that is my setup for cyclecommuting, even during the daytime.
I think this (edit: blue lights) is intentional, at least in some cases. A highway police officer on night patrol is probably well served by this potentially disorienting effect.
I disagree. I once almost didn't see an officer who was standing in the halo of her car's flashing blue lights on a rainy road. Intentionally disorienting drivers is dangerous.
I wonder if visibility could be helped by leaving some flashing in the tailights when they're full-bright : when the brake-light mode is activated.
(I mean LEDs that are dimmed by flashing them on and off at a rate faster than persistence of vision.)
Another visual thing. This is a pet peeve. Emergency vehicles use flashing BLUE lights. That's perceptually stupid. For one thing, human eyes, opened up (wide pupils, typical at night) do a better job of focusing longer wavelength light. This has two consequences: -- it's slightly harder to locate the source of the light because it isn't as neatly focused on the retina. -- the poorly focused blue light splatters all over the retina, desensitizing the rods of peripheral vision and spoiling dark adaption right when it's needed - entering into a zone where an emergency vehicle is active.
Secondly, red light-- deep red light -- selectively desensitizes the cones in the fovea, leaving the rods in peripheral vision sensitized.
Conclusion: orange light would be a much better choice than blue for cop car flashing lights. It would focus better, preserve dark adaptation better, and preserve nighttime peripheral vision better.