As anywhere in the world driving under the influence it is not advisable. In other words....dont do it. The Korean police in Seoul are red hot at certain times of the year when it comes to alcohol tests. They block the bridges and set up road blocks (booze busts). Christmas, New Year and also Chosok are the most likely times that you will be pulled over. Fines and suspension of your driving license is a surety if you are caught.
It seems in Seoul that red traffic lights are merely a suggestion. The main offenders are taxis and buses, however there are many instances where all traffic just keeps on going. Be careful when you take off from a green light that there is no traffic coming the other way.
This is also another trap for new players. DO NOT be the first one the step off the curb. Just because there walk light has turned GREEN does not mean that the traffic has stopped. Quite often traffic will continue for at least a few cars or one bus once they have been given the RED light to stop. You have been warned.