[It's sad to think that Clark Kent has to travel to West Palm Beach, Florida to change into Superman these days.] [1]
Now that I think about it, it seems strange that Clark [2] would even consider using a phone booth for changing into Superman. They aren't known for being all that spacious (unlike British police boxes [3]) and they lack any sense of visual privacy.
And yet, here we are, Clark in mid-change.
[1] /boston/2017/12/09/superman.jpg
[2] https://www.supermanhomepage.com/comics/who/who-intro.php?topic=kent-clark
[3] http://www.themindrobber.co.uk/real-police-box-history.html