There has been a lot of discussion about GPS units in our Vanagons over the
years so I hope this is on topic.
Thought I'd relate a frustrating experience with a GPS unit I have been
playing with in Starwagen.  Last week, taking a slow meandering route home
over several days after the WetWesties Unsuperbowl event at Nehalem Bay
State Park on the Oregon coast, Phil Zimmerman and I were essentially stuck
with traveling I-5, the main North-South freeway/Interstate through
Washington and Oregon.  Phil suggested we might look up a shop/store/guy we
both had an indirect tie to.  Phil didn't know exactly where the shop was
but did remember that it was on a short road with a unique name near the
town of Chehalis in Washington.  So, we grab the GPS, do an address search,
and sure enough, there is the little road.  So I push the button that sets a
route to that location and bingo, we are on the way.  Ah ha, take this next
exit (into another small town).  Turn here.  Turn again. Turn again and we
seem to be going in circles.  And we are about 30 plus miles from where Phil
remembered the place being.  And the GPS still trying to turn us around.  So
we pull over and park.  Break out my laptop with Streets and Trips.  Find
the address immediately, about 35 miles up the freeway and it's going to be
easy to find, right off a major road I was already familiar with.  So back
onto the freeway and head in that direction.  But the GPS was still trying
to turn us around!!!  Then I had a thought and went to the menu on the GPS
and checked one of the settings, Road Preferences.  It turns out there is a
preference setting for Interstates.  "Permitted", "Avoid", or "Forbidden".
At some time in the past I'd set it to "Avoid" and that is exactly what the
GPS was trying to do, keep us OFF I-5, the Interstate Freeway!!  And once I
reset it to "Permitted" it took us right there (even though at that point we
didn't need it).  But, for a while, we had a lot of good laughs as the 'damn
dumb' GPS (pretty smart after all).  Another example of be careful what you
wish for (Blue Highways), your GPS just might give you what you said you
wanted but didn't want right now.