That momentary flash is also useful as an aid to passing trucks.   It is
their practice to flash their headlights at each other when one truck
passes a slower one.   The truck being passed flashes his/her headlights
when the passing truck's last trailer is far enough past his nose to allow
the passing truck to come back safely into the right lane.  I imagine it it
difficult to gauge how long your trailer(s) are using just the mirrors on a
big rig, especially when you are on a busy interstate. There are lots of
impatient drivers who have no idea of what a trucker can see, etc.   I've
seen them swoop impatiently into the right lane to go around a passing
truck...trapping that truck in the left lane and risking getting smooshed
if they happen into a blind spot in the trucker's mirrors.

   Truckers seem to appreciate your 'flash' and will blink their running
lights in return for your courtesy 'all clear' signal.

On Tue, Oct 1, 2013 at 6:05 AM, Mike B <mbucchino@charter.net> wrote:

> You're describing the "Flash-to-pass" feature which is a european
> requirement, IIRC.
>
> It's designed for a manual momentary "flash-flash" operation, not to be
> held that way for continuous use.
>
> It's an excellent way to get home if your headlight switch fries (giving
> you NO lighting), as happened to me one particular dark and stormy night
> in my '87 Westy.
>
> Mike B.
>
>
> On 10/1/2013 12:07 AM, JRodgers wrote:
>
>> Was there ever a model year of Vanagon with dual headlights where both
>> high and low beams were on at the same time??  Like low beams are just
>> on  and when the dimmer control switch was pulled the brights come on
>> and the low beams remain on as well? Or something simmilar?
>>
>> Just curious.
>>
>> John
>>
>