Flashing lights are the lights where the period of darkness is more than the period of light.
There are four types of flashing lights -

1. Flashing Light (Fl) : Less than 50 flashes in 1 minute – approx 1 flash per second
2. Quick (Q) : Between 50 and 80 flashes per minute; approx 2 Flashes in 1 second
3. Very Quick (VQ) : Between 80 and 180 flashes per minute; approx 3 Flashes in 1 second
4. Ultra Quick (UQ) : More than 180 flashes per minute; too quick to count