[Sir Gawain]

Maybe I'm mistaken, but I think I've been through some intersections that do not have an "all red" phase.

[Alberta's Child]

I may not have been clear about that. An "all-red" phase is not required -- it's just that it is often used at busy intersections and/or intersections with higher speeds where it hadn't been used before the 1980s or thereabouts.