This is a tutorial on setting up American Truck Simulator to run on Triple Monitors or screens that are different resolutions and/or refresh rates (Hz). This uses the SoftTH utility which can be downloaded from the link below. The only unfortunate caveat is you have to run an older version of ATS (1.35) so you won't be able to use newer DLC. The newer versions of ATS do not support DirectX 9.
http://www.softth.net/