Investigating the speech of the English upper class in 1956, the linguist Professor Ross identified U(pper) and Non-U(pper) features. ‘Pardon’ was a non-U term used
 
1. When the hearer didn’t hear the speaker properly; 

2. As an apology (eg on brushing by someone in a passage); and 

3. After hiccuping or belching. 

The U equivalents were (1) What? (2) Sorry (3) (Silence).

These days, I suspect AmEng uses *Excuse me* more often for (1) and (2) than does BrEng, which prefers *Sorry*. BrEng mainly uses *Excuse me* for (3) and perhaps AmEng does too.

If you bump into someone on a British street, the bumped is just as likely as the bumper to say *Sorry*.