Boolean

In essence, this refers to simply knowing "IS there or ISN'T there?" something relevant to you just continuing the same along the road.

This could be a car approaching you, or a bend in your road on a foggy day.  (It would not include if the handbrake's On or Off).

This is because the first two circumstances can be answered Yes or No: there IS a car (or a bend) or there ISN'T one.  If Yes, the danger rises so consider making changes.  (If you can't be sure, assume Yes!)

The handbrake question isn't just a "is there? / isn't there?" a handbrake; it requires assessment.  But assessing should come later.  The first step is just to identify presence or absence of more risk.

If you share my background, you may recognise George Boole (whose name this Yes/No thought carries) and Erwin Schrödinger (who later explained how the physical world doesn't follow such straightforward rules!)