24-hour traffic jam is an everyday reality in Seoul. During the drive from the airport to your destination, expect congestion as you enter the city – even at midnight. I am serious. As one gets stuck in the traffic, one cannot help but wondering what Seoul people are doing on the street at midnight. Talking about nightlife and a sleepless city!
Also expect American landscape – big clean highways and skyscrapers. I noticed the roads are better lighted than in the US, though. On the university campus, the walkways are brighter as well. When I mentioned this to my Korean friends, they told me the US is too big to light. The better light, however, has nothing to do with concerns about safety because Koreans have a different sense about it for sure. For example a long staircase does not always come with a hand rail.
anvi hoàng 
Also the concept of light is different? In the US, people drive everywhere and pedestrian streets are not as used and established as other countries. Some cities in the US, like Tucson, AZ, limit lights to reduce light pollution. Light or not, the city seems to be super clean, day or night!