You can see on the road that it takes up one lane like the cars and is equivalent to about 2.5 cars lined up accounting for gaps. Also the point of this post is that if public transport was normalized then this bus wouldn't have six people in it because half of these cars would be people on the bus instead.

On the road, 4 cars would take more space lined up one behind another.

I don't know what the law is where you live but i know what it is where i live, so excuse my weird metrics for a sec while i explain how wrong what you said is.

In order to facilitate proper reaction time for yourself as the driver, you must have about two "seconds" (as in if you stared at the road beneath the car in front of you, your car would be there in about two seconds) between your car and the one in front of you.

Meaning the faster the vehicles are, the larger the gaps, and if we're talking 4 vehicles, it's 3 gaps.

For maneuverability's sake, it's worth mentioning the "wave propagation" that happens during brake time, but I won't get into it.