One of the ways that car manufacturers have devised to alert drivers that a turn signal bulb is blown off (and thus a safety hazard), is to blink the lights very rapidly. They determine that by sensing the total bulb's current, and if a bulb is blown, it will fall below a pre-determined threshold, and the controller will then alert you.

Since LEDs consume less current, the total current will fall below that threshold and then you've got this blinker on steroids...

I love how LEDs look in automotive applications...since its color is a single wavelength to start with, (i.e, light did not start white and then was color-filtered) their color is very deep, very intense.

There are some stunningly beautiful yellow LEDs, but they are more expensive than red LEDs.