I agree and my bias shows in that, as Moderator renaming this thread, could not bring myself to insert the "Urban" into Regional Rail, but still, in the interests of search-and-find, think that people are going to be searching for RUR and NSRL. And the act of renaming (away from Commuter Rail and toward something that evokes an all-day mode), was a pretty big political shift and victory for TransitMatters, even if the actual branding sucks.
ArchBoston, and Railroad.net have used
RER as shorthand-brand until now. RER is a French (originally Parisian) acronym
Réseau Express Régional (transliterates as Network Express Regional or Regional Express Network), and is not particularly catchy either though transit nerds know *exactly* what is meant by it.
London calls their (rough) equivalent the
London Overground to stress that it has subway-like operations, but is surface rail.
If we wanted to Backronym RER to mean Regional Electric Rail, that'd be OK by me.