These are things like watching the angle of the front wheels, the speed at which other cars are taking the intersection (faster = going straight through; slower = taking the turn), but also how much time it takes for a stopped car to start moving so you can judge whether you have time to enter the intersection.
This is a learned skill, and not everyone in the general population has the cognitive capacity to reliably pick up on these cues.
I’m not saying that I’m Nigel Mansell, but I genuinely think that the inability to pick up on these cues is why many are terrified and opposed to them.