If you were travelling in a car at the speed of light...

I'm gonna let you in on a big secret... relativity is a bunch of bullshit, just like evolution.

Moves with the vehicle.

No it wouldn't move with the vehicle (this is a key point of relativity). The light would move toward us at the speed of light (including in our frame of reference). It would be redshifted meaning the wavelength of the light would get longer.

this was a joke by Steven Wright.
"If you were driving your car at the speed of light and turned on your headlights, would anything happen?"

Johnshead, your questions have a basic problem. You are confusing frame of reference. In relativity the frame of reference (in this case who is measureing the speed) makes all of the difference.

How would you know that this car is traveling at a speed very near the speed of light?

A possible answer is that you might see me traveling away from you at near the speed of light and conclude that I am stopped so you must be the one moving. But you could look at it another way, the car could be stopped and I could be the one moving away.

A car that is moving at near the speed of light in one frame of reference is stopped in another frame of reference. If you are in the car, the car would appear stopped to you and you would measure the light moving out of the backlight just as it does in any stopped car.

Nooooo; Bullshit is how YOU keep your EARS apart..

Ok, I think I get what you mean. What I meant was; what would the light look like to an outside observer?

A basic fact of relativity is that the speed of light is a constant. Any observer will see light moving at about 299,792,458 m/s.

The speed of any object moving slower than light will be measured differently by different observers. But, every observer will measure the speed of light the same.

There is a huge distinction between light speed and very near light speed.