Barry wrote in message
news
Is "fly parallel to V157 offset 2 miles to the left" something
that I might ever expect to get in an IFR clearance if I file /G ?

One of the concerns with GPS is that the great accuracy can sometimes
increase
the probability of a midair collision compared to conventional nav.
Consider
two aircraft traveling on the same route in opposite directions at
different
altitudes, in non-radar airspace. If, due to a pilot or controller
error,
both planes end up at the same altitude, the probability that they
would hit
was quite small with VOR, but much higher with GPS. Some airline
pilots have
already started flying lateral offsets on their own, and ICAO is
studying the
issue and trying to come up with standards. One of the proposed
criteria is
that the procedure be transparent to the controllers. So it's
unlikely that
ATC will ever assign a clearance to fly an offset, but at some point
pilots
might be permitted or required to fly an offset on some routes.


This FMS/GPS-assisted mid-air risk is what I have seen discussed in
numerous big-iron forums and an ALPA magazine. In both places the
discussion seemed to favor a small offset, say 1 mile right of
centerline, to avoid nose to nose meetings.

--
Scott