I've often been worried about this, especially with the LOW and often dim tail lights. (add a film of Diesel soot and they're DIM)

on the rear overhead shelf/parcel tray I'd added a full width strip of the reflective tape like used on Semi's 

the idea is it works wether i'm driving it or not.   parked on the side of the road it still works, and lights up well in headlights.

also doesn't add interior glare on the back window making it difficult to see out,  
to watch for those tailgaters and such .. 

Dan 

From:    John Lavery <systems007@YAHOO.COM>
>Subject: 3rd (center) Brake light for late model Vanagon
>
>Hi all,
>
>My van got rear-ended recently while motionless at a stop light.
>Foruntely, it only destoyed the rear bumper--no additional damage that
>I know of.
>
>This has got me thinking about adding a third brake light to make it
>more obvious that I've got my brakes on.  Although I'm unable to find a
>link at the moment, I know there are some folks who added a third
>(center) brake light to their Vanagon.
>
>I've seen a 3rd brake light mounted in the area behind the A/C.  In my
>case, the light would have to be bright enough to be easily visible
>through the dark tinted window on my rear hatch.
>
>Anyone know if there are some kits available, so that I could easily
>make this upgarde?
>
>Thanks,
>John
>'87 Westy