Today I took the above photo of the platform at at the University City, Philadelphia, train station. For some time, I have been noticing “Watch the gap” announcements and signage not only in the Philadelphia commuter train system, but also Amtrak and Metro North, which serves the New York metropolitan area.
The phrase “Mind the gap” is, of course, intimately connected with the London Underground and has been since 1969, when it was adopted to caution passengers not to step into the space between the train and the platform. Gap isn’t a proper Britishism, I don’t think; it’s just that there isn’t any American counterpart, so the association with the Underground slogan makes it sound British.
Mind very much is a Britishism, so much so that I don’t expect to see it catch on in New York or Philly. However, Seattle–the home of the Bumbershoot Festival–has, according to this Flickr photo, put the slogan on public buses. I don’t exactly understand what the gap is on a bus, so if any Seattle-ites could fill me in, I would appreciate it.
notoneoffbritishisms.com 
I’ve been to Seattle but once, in the 1980s, so I can’t help you there. But, once again, my grandparents, both of British/Irish and German origin, were constantly telling me half a century ago to mind this or to mind that, so “mind the gap” seems much more natural to me than “watch the gap”. Why on Earth would I want to stand around and watch a gap (unless it’s the Grand Canyon or some such wonder)? “Mind the gap” means to “watch out for the gap,” not to watch it. Methinks this may be another case of American abbreviated signage (perhaps to save taxpayers’ money?) that alters the intent of the meaning.
I still hear “mind” used frequently in the southeastern US, but in the sense of “obey” rather than “be aware of.” “You kids mind your grandparents while we’re out.”
“Mind” is from “Be mindful” meaning pay attention to, or be aware of.
But there is a British expression “watch out” – meaning be careful or be alert..
Perhaps “Watch” the gap is a NOOB?
The “gap” on a Seattle bus (or any bus I would imagine) would be from the step to the kerb or platform, similar to those found on a subway or train.
Specifically in relation to Seattle, the platform in the 3rd Avenue bus tunnel is the same height as the bus step; if the driver is good/careful the gap is only an inch or two. Other times, it can be several feet.
Nice Seattle “mind the gap” photo, btw! 🙂
“Mind how you go” for “take care” or “watch yourself” was always a traditional saying of the English policeman, along with “Move along now, please” and, more apocryphally, “Let’s be ‘avin’ you” and “‘Allo, ‘allo, ‘allo”. I remember hearing it frequently years ago, but I would guess nowadays it’s become confined to mustier stage productions, which date from the time before bobbies came off their beats and started driving around in patrol cars.
Tops for admonitions with the word “mind” is the following, good for double-entendre giggles:
“Mind your head”.
Found in England wherever a someone might inadvertently bash his/her head into a low overhead structure when passing through a tunnel with a low ceiling (such as in the London Underground) or through low doorway (such as in many 100-or-more-year-old buildings surviving to house pubs, B&B’s, etc.), and, btw, the overhead beam of a doorway is actually called a “header”, both in Britain and in America.
“Mind your head” is of course also reminiscent of the caterpillar in Alice in Wonderland, which of course, inspired Jefferson Airplane’s famous chant, “Feed your head”.
Speaking of throwbacks to the 1960’s, how about the following double-entendre, also found everywhere in Britain (including the Underground and theaters (sorry, theatres) and hotels, even, God forbid, in cathedrals and churches), namely:
“Way out”
P.S. Isn’t “giggles” another Britishism (although perhaps with a more mischievous meaning that I have intended)?
“Way out” reminds me of one of my favorite quotes from “Winnie The Pooh,” about visiting the zoo.
“There are some people who begin the Zoo at the beginning, called WAYIN, and walk as quickly as they can past every cage until they get to the one called WAYOUT, but the nicest people go straight to the animal they love the most, and stay there.”
It has no meaning except in the bus tunnel where the bus step is at the same height as the platform.
“mind” the gap means be mindful of, be aware of, the gap. “Watch” the gap means stare at it… why, whats it going to do?!
Um, the gap on a bus would mean the gap between the ground and the first step…
You can also mind a baby or young child, as in take care of.
Also, “who’s minding the shop/store?”
My grandma’s generation (born 1900ish) in the north east of England would use “mind” for remember, as in “Do you mind the time when….?”
I can say that at least in Canada, everyone uses ‘Mind the gap’ and on Toronto’s TTC system, all vehicles and subway stations have stickers with mind the gap and a pictogram. Interesting British v American historical difference even though Toronto and NYC are geographically near.