A great number of drivers now seem to have no familiarity with the concept
of passing on a normal highway with two way traffic.  They seem absolutely
baffled by the concept of waiting for a safe sight-distance situation and
going around a slower vehicle by using the oncoming traffic lane.  I see
this very often where I travel, as I try to avoid interstates.    So, there
you are, traveling along at 65mph out in Nevada, Wyoming, Utah...some
western state with wide open spaces and two lane highways and up comes a
faster driver behind.   Then they follow you for 10 miles!  I have been
forced to slow up to about 20mph to encourage a particularly meek driver to
get his brights out of my mirrors at times.
  Or, you come up behind a row of vehicles, stuck behind a slower truck or
car...chance after chance to pass is missed by the clueless car just behind
the slow vehicle and nobody in the line has the speed or the safe distance
to get round both the truck and the 'scaredy-cat' or the city fellow who
doesn't know it is OK to go around slower vehicles....
  In Baja, Mexico, it's the custom to indicate it's safe for passing by
putting on your left blinker when someone is behind you and is itching to go
round.  When you can see ahead that it's clear, you flip on the blinker and
the fellow goes right round.  If you are going to be turning left off a
highway, it's customary there (Baja) to pull across the line and turn from
the oncoming lane so that people headed in your direction don't have to slow
up while you do your turn..
  And here in the Northwest, we seem to have more than our share of left
lane slow drivers on the interstates.  Between Portland and California on
Interstate 5, I usually encounter about two dozen that I must pass around
the right side, even in my VW vanagon...
  Don Hanson