The Airport Railroad Express is perfectly opened on 29 Dec 2010.
From Incheon International Airport to Seoul Station, take less than 1 hour.
AREX is not effected by traffic situation and weather.
AREX can be separated Express and Regular train.
Regular train is a kind of commuter train, stop all station.
Fare is depend on a distance, maximum fare is 3,700 KRW.
3,700 KRW is for Incheon International Airport ~ Seoul station.
This train takes 53 minute between Incheon International Airport and Seoul Station. Running 356 times per one day.
Express train, fare is 13,300 KRW.
Running 66 times per one day.
This train take 43 minute between Incheon International Airport and Seoul Station. It just stop Incheon International Airport and Seoul Station.
I was wonder why Express train fare is almost 3 time of Regular train fare.
Express train just 10 minutes faster than Regular train.
Finally I found reason, only Express train passenger can use Seoul City Air Terminal. Express train passenger can boarding and sending your baggage at Seoul City Air Terminal before 3 hours takeoff time.
But this service is only for Aisana Air, Korean Air and Jeju air.
More detail, you can get at Public Website.