The units run on 25 kV AC overhead line supply via a Brecknell Willis high speed pantograph, using four Brush TM2141B traction motors. With much shorter passenger journeys in mind, the Class 320 units originally lacked the toilets of the Class 321 units and also began life with a lower speed capability () due to the much closer spacing of stations on the North Clyde Line. The lower design speed meant that yaw dampers could be omitted from the class. However, yaw dampers were fitted across the class in 2010, allowing them to run at . This meant that the units could be used on the sections of the Argyle Line route shared with the West Coast Main Line (and in theory, the Airdrie-Bathgate extension of the North Clyde Line and beyond, although this is currently prevented by a lack of DOO equipment) and also allows full-speed running in multiple with the near similar Class 318. Their interior design includes paintings of various landmarks and famous sights along the various SPT rail routes on the car ends.