It is a relativistic effect so it depends on the relative velocity with respect to your vehicle. 

Imagine that your car is moving close to the speed of light relative to some road (let us forget about the physics of your car and the road for this question). If you are inside the car, for you the lights are in the visible spectrum. For somebody still with respect to the road, let us call this person *P*, there is what is called a Doppler shift. *P* will not measure the EM radiation with the same frequency as you.

The Doppler shift depends on the relative velocity (direction). If the car is moving towards *P* at relativistic speeds, then *P* may detect gamma radiation (frequency goes up, blueshift). If the car is moving away from *P*, the shift is in the other direction and *P* could see may detect low frequency radiowaves (frequency goes down, redshift).