I was out shooting long exposure shots of streetcars when a couple of ambulances passed by right where I was shooting. I just took the shot with the settings I already had and it all turned out great.
This is in Sweden. We have blue lights on police cars, ambulances and fire trucks here :)
Love it. I'm somewhat surprised that the LEDs doing their pulse width modulation thing wasn't picked up in the photo. Maybe DC driven lights are less prone to it than AC, or maybe these have a better power supply than most cheapie home AC powered bulbs.