How do you determine what a safe distance is at a red light?

What do you mean? Space between you and the car in front of you? Space between you and the stop line?

Where the line is drawn, but if you meant how far you should be from the car in front of you; you should be able see their tires when you are in complete stop.

My defensive driving instructor said you should always be able to see the tires of the car in front of you.

So it’s safe to stop under this?

If you’re the first in your lane, then stop behind the walking portion, usually marked with white. If there is no marked walking portion, look for the nearest curb, extend it in your mind to meet your lane, and stop behind that. If there is no curb at all, stop a good few meters behind the intersection.

If you are behind another car, you should maintain enough of a gap in front such that you could signal and pass the car without having to back up, cause odds are you won’t be given any space to do so by the guy behind you. This makes situations like the car ahead stalling much more manageable, and also gives you a good amount of space around your car which is good to have in general.

@Marina Exactly what I was told as well.