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.
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....