Usually you can use the general forms of people you see as reference. A person walking along the road generally looks pretty similar so if you can nail that shorthand it doesn't really matter if you're getting a likeness or anything. No one's gonna know if those cars were even there or not. So just pick a car out or a person out and draw inspiration from the scene. Maybe someone's wearing a nice hat nut isn't in the right position. Stuff like that.

So yeah, lots of memory. Just using what the scene gives you and working it to your paintings needs!