Bank holidays are never a problem on the N7/Naas Road, and also as it turned out yesterday there was not one hold up on the N7 all the way to Newlands Cross, thank you truckers on strike!!. But I'm guessing that you have never experienced it on a "normal" day with traffic back to Kingswood interchange(good day), City West interchange (normal day) or back to Rathcoole (bad day).
Stick to the train!!!!!