Q:

Is there a way to create a flickering frequency to be dependent on speed of the person looking at it?

Is there a way to  make a screen or a road sign flash at different rates, depending on the velocity of the observer looking at it?

I would like to achieve a state where two observers going at different speeds would see the screen flash at different rates at the same time.
another thing i would like to check if possible is - is there a way to make the observer see a different image depending on his/her velocity? (without a radar).

A:

You can use a reflector with gaps.  Then the light from a car will alternate between reflecting and not reflecting at a rate dependent on their velocity towards the reflector.  Please excuse my crude diagram:

As the car moves right to left, gaps in the reflector will cause it to appear to flash on an off.

