Here in the US of A, one shouldn't expect slow commercial traffic to
indicate when it's clear to pass - - not since lawsuits became so
popular, anyway. We were told back in 1981 never, ever, wave or blink
to let someone know it's OK to pass, as the signal could be
misinterpreted, and the resulting accident could make the signaler
legally liable should the  signalee misunderstand and have an
accident. Also I might mention one shouldn't expect a loaded truck to
pull over and stop for you to pass on a 6-plus-percent grade, either!
Most mountain grades have a pull-over on the summit, or a passing lane
or two on the upgrade. I'm sure things will change when we all have
flying cars!  ;^)

Gary (who will pull over to let you by if it's safe to do so!)

>
>>
>>  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.
>
>
> Yes, but in Africa you put on your left blinker to tell them it's not safe
> to pass, and switch to your right blinker when it is safe.  So make sure you
> know what the practices are before you follow those signals!