Please take note if you're in Korea and planning to make use of the free shuttle services between Seoul and Busan.
Between July 1 and August 31, the route is as follows:
Gwanghwamun 8:00 - Lotte Hotel Seomyun, Busan 14:20 - dep. Lotte Hotel, Busan 16:00 - arrive Seoul 22:00
Also the service will be stopped temporarily betwen 9th and 14th September to avoid the traffic snarls during the Chuseok holiday season.
For more information, click here.
source:
http://english.visitkoreayear.com/english/benefit/benefit_07_01_01.asp