When is a door a ドア and when is it a [扉]{とびら}?


I've been in Japan for the summer and noticed that the announcement for the
closing doors (in the Kansai area, at least) on trains is always 扉が閉まります.
However, the equivalent announcement on buses appears to be a toss-up between
扉が閉まります and ドアが閉まります.

Is there an accepted distinction between 扉 and ドア? jisho.org gives ドア as a
Western-style door and 扉 as a (generic) door. Are there any other
distinguishing nuances?




I always think of 扉 as sliding doors (as also usual in trains and buses), and
of ドア as a door with hinges (or some other more modern/Western construction,
like elevator doors).

See 類語例解辞典《小学館1994,2003》

> ① 「扉」は、[蝶番]{ちょうつがい}などを軸に回転するようにして開閉する機構のものも左右に開閉するものもいう。

(「扉」 is used for both doors with hinges and sliding doors)

>
> ③「ドア」、主に[蝶番]{ちょうつがい}で開閉する機構で洋風のものをいうが、「自動ドア」の場合は、左右に開閉する機構であるのが普通。又、「ドア」は、出入り口以外には使わない。

(「ドア」: mainly for doors with hinges; except for automatic doors, here it is
common for sliding doors as well; only used for entrances/exits)

I suppose, when thinking of a western-style door, one associates it with ドア
first, as it has got the more specific term ドア. Thus, 扉 is associated
_especially_ with sliding doors, _in contrast to ドア_. But as a general term, 扉
may refer to other kinds of doors, as evidenced by the [広辞苑]{こうじえん} definition
[開]{ひら}き[戸]{ど}の[戸]{と}, and 扉 comes from [戸片]{とひら}.

