Matt,
It may cause some confusion in Europe as side markers have never been a requirement, however, i think ppl will be quick to pick up on the difference as we use dual filament bulbs to accomodate the purpose. as a result, even with side markers on, you can easily see that a car has his flasher on.
Another option that is used here is to have the flasher override the side marker function so that side markers are normally on, but when using the flasher, the light will alternate between on and fully off. IMHO the former system works better.
We are starting to incorporate repeaters here in north america as well. Particularly on the european imports
. However, as in eurpoe, the repeaters remain unlit unless used as a turn signal or hazard function (4-way blinkers). Basically, they are not wired to coincide with the standing/parking/marker lights.
The side markers serve not only to make a car more visible from the side, but also to help discern which direction it's travelling in as the rear sides are red.
I think that the drivers in europe are generally more alert than drivers in North America and are used to IDing cars after dark w/o side markers.
I reactivated my sides because I just don't have that much confidence in the drivers around here, and since it's regulated that all vehicles here have some form of illumination for side-on situations, i don't want to risk getting pinned for an accident that wasn't my fault on a technicallity.
Strictly speaking, my car is illegal right now because i haven't got side reflectors up front.
I believe that european specced cars tend to be far superior in most areas, however, i think that they could also stand to benefit from the addition of side markers.