But as far as I know, the train is for Schengen passengers. People would clear immigration in T4S and take the long set of escalators down to the train station, and then clear passport control again when they reach T4 plus security. While it's not an issue for me as an EU citizen or other countries that are visa free, I wonder how the process is for those who do require one since there is a chance that they slip away while transiting. What plays out in my mind is after clearing transit security in 4S, there is a shuttle somewhere that goes to non-Schengen T4 but I cannot seem to find the details anywhere.