But if we were to modify signal positioning to make it impractical to stop past the white line, fewer people would overshoot and wait.

We do this kind of thing in many other places in life. Imagine if we didn’t use barriers anywhere and only used painted lines to tell people where to be - don’t walk to this side of the line, that’s where the valuables are “stored” (no walls, just markings.)

We use ‘guardrails’ all over the place. Sometimes to nudge people (one can jump a literal guardrail), sometimes to prevent injury (you simply cannot physically access the active industrial robot without intentional effort), and all kinds of inconvenience in between to suggest where to be.

Place the lights so that they’re only visible further back, and people will stop further back.