Hi*SS, I don't know how long you have had you smart but if it is a typical G&K smart you don't have fog lights up front, those are the parking lights/turn signals. They come on with the first position of the headlight switch, the next position is the headlights and the third position is the rear fog which is where you would normally find the left back-up light. If you leave your lights on, turn off the ignition and open the drivers door you should hear a warning "bong". Your parking lights will be on but your headlights will be off. The ignition turns off the headlights and the drivers door opening sounds the "bong" which reminds you the switch and parking lights are on.
Now that I reread you post, the above describes the coupe, the cab has a different tail light but I'm pretty sure the function is the same.
Cheers, Dan