The effect described in the StackExchange answer to increase perceived brightness at a lower power level seems to rely on a low frequency and short duty cycle.

The effect described in the StackExchange answer to increase perceived brightness at a lower power level seems to rely on a low frequency and short duty cycle. It's not necessary to use that effect given that LEDs rated for higher power levels are available, and the amount of power is insignificant at the scale of a car, but it does allow the use of cheaper LEDs.