"TheOneKEA" wrote in message
ups.com
Why does the M40 terminate so far outside London? A quick check of
aerial photos and a map shows that the A40 Western Avenue runs through
mostly open land between the M40 terminus and the A312 Church
Rd./Mandeville Rd. roundabout junction, with all of the junctions in
between fully grade-separated. With the M40 extended to the Church Rd.
junction, the A40 could be diverted along the path of the A4020,
running through Uxbridge and Hillingdon as far as the A312 roundabout,
where it could turn north and intersect the M40 at its new terminus.

Is there some particular reason why the M40 doesn't terminate closer
in to London? (i.e. the existing road needed to retain full access?
NIMBY? lack of money?)

The junctions weren't always grade-separated, and now that they are,
that part of the A40 usually flows smoothly. There doesn't seem to be
any point spending many millions to increase capacity round Uxbridge and
Ruislip when the choke points and flat junctions on the A40 are further
into town -- there's a long tailback every morning, which wouldn't be
helped in the slightest by extending the M40 to the Target roundabout.
There had been plans to widen the A40 near Wormwood Scrubs in the 1990s,
but they were dropped about a decade ago.