1. The use of 'am/is/are to'
'Be to' is used to refer to the
future when the actions are subject to human control. Thus statements such
as I'm going to faint or It's going to rain cannot be
expressed with 'be to', which has restricted uses: e.g.
2. The use of 'be about to', 'be
on the point of'
These constructions are used to
refer to the immediate future:
'On the point of' conveys even
The use of just with
'about to' and 'be on the point of' increases the sense of immediacy, as
it does with the Present Progressive:
3. The use of 'be due to'
This is often used in connection
with timetables and itineraries: