[magmastonealex]

I'd like to think it's become ubiquitous - it has been a while since I've seen a signal without a red clearance configured.

However, the Federal Highway Administration in the US (which sets guidelines, but most states define actual rules at the state level) still says in their Signal Timing Manual [1]

> The use of a red clearance interval is optional, and there is no consensus on its application or duration. [...] there may not be safety benefits associated with increased red clearance intervals.

and goes on to describe how it has negative traffic flow implications.

so I suspect at least some agencies out there still are not using them.

[1]: https://ops.fhwa.dot.gov/publications/fhwahop08024/chapter5....

[pests]

I feel like my area (where I've lived my whole life) does not have red clearance interval. It's not something Ive paid attention to before.

I'm sure it's proper driving technique but I feel it's ingrained in my head to give a couple seconds when a red turns into a green for all cross traffic to finish / anyone who runs the light. It's a common thing around me and I don't think it would be happening as much if an all-red period was implemented.