It probably just attempts to indicate it's the same 3 cars again, likely pointing out the fact that there are legitimate reasons to drive, those people are just fucked by everyone else and brain-dead traffic planning.

It looks like the green cars have passengers, while the red cars have single occupants.

Nevermind, some of the red cars have passengers, too. I guess the green cars survive to the final graphic… why that’s relevant, I don’t really understand.

I think it’s more for design language, you’re subconsciously drawn to the green vehicles because they’re different, and subconsciously when you’re looking at the traffic, you’re reminded what it’s like being in the traffic yourself.

So you imagine yourself as the green car.

1st scenario: traffic is really bad. 2nd scenario: they’ve added more lanes, but you, the green car, are still stuck. 3rd scenario: public transportation has alleviated the traffic and it’s better for all.

Notice in the 3rd scenario, all the transportation is green. I think it’s to make you think, “I can ride my bike to work” or “I can take the bus” or “I can still drive my car if where I live requires me to” depending on your own situation. It’s to show all options can be viable, if you support public transportation.

That’s how I see it at least.

I was thinking it's electric?

I assumed that Green = Moving. The pedestrians in the city are green, as are the busses and bikes in the bottom diagram. The greens in the top two are there to show just how few vehicles can actually move at any given time.