

I suppose I may have found it more obvious than you that this image was taken in the United States, which possesses a plethora of places that look like this. I did try to look up RPS guardrails to get a bearing on the context you were coming from, but didn’t come up with relevant results, probably because the search engine is biased for English/American results to English/American queries. You mind me asking where RPS is from?
It’s might not be a payphone, it might be an emergency phone. Never been to Korea, but some really long bridges in the US will have these spread across the bridge span so that if you break down and don’t have access to a working cellphone, you can walk to them and call for assistance after pulling over. The Chesapeake Bay Bridge Tunnel comes to mind