Hi @ouyou. The English Wikipedia has this to say: > The trains have a design speed of 120 km/h (75 mph), but are operated at a maximum 110 km/h (68 mph) on surface tracks and a maximum 100 km/h (62 mph) in tunnels. I see the side note about the 180km/hr in 2012, but there is no mention in the article and no source on that information. As well, the Korean version of the article cites the max possible speed is 160, while the actual operating speed is given as 110. Can't speak to any other figures beside what are printed there as I'm really not sure. Perhaps that 180km/hr figure is in error?
Yeah seems like it. But even the current end to end time doesn't seem to meet the quoted 100-110km/hr figure.
There does seem to be a discrepancy. My guess for the actual speeds is that 100/110km per hour is the _maximum_ speed, plus stop and go must be factored in. So a drop from the maximum of 100 to an average of 85 doesn't seem implausible. Reference to the 180km/hr figure appears to have been added to the [article in 2010](http://en.wikipedia.org/w/index.php?title=AREX&oldid=393808840) and links to articles about adding KTX service, as well as sharing rails with line nine. I believe this is the source of the erroneous 180km/hr prediction.
Hey Philip and ouyou! I think that Philip's explanation is correct. The A'REX can't reach 180 km/h. This article from 2007 mentions an average speed of 72 km/h and a max of 110 km/h: http://www.hani.co.kr/arti/society/area/190537.html That was for the first phase Incheon to Gimpo, probably now the average speed is higher and closer to the 85 that both of you mentioned.
PS: We just opened a special page for any [travel information on the Incheon Airport Train AREX](http://kojects.com/incheon-airport-express-arex/).