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....
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.
This was definitely true in the past, I feel like the concept of a 'red clearance time' is something that only became common within the last 5-10 years. Do you think it has become (with rare exceptions) ubiquitous at this point?