The SMU220s were introduced into service in 1999 to help boost service numbers on recently upgraded lines such as the triplication to Lawnton, and most notably they displaced the last remaning loco-hauled services around Brisbane (the last being #39P0 from Shorncliffe on 2nd November 1999). 42 of these units were built by Walkers/Adtranz at the Walkers factory in Maryborough, Qld.

The SMU220s differ only in a number of respects to their older cousins, the SMU200s. The use of AC traction motors is continued, however with a much quieter traction cooling package which is based on oil cooling, as opposed to the blower fans used on the SMU200 and IMU100 units. The air-conditioning is provided by one large roof mounted pod, as oppose to the smaller ones on their older brethren.

The doors are push button operated and can be ‘queued’ to open for the next station by pressing the Door Open button between stations. The SMU220s are fitted with a Digital Voice Announcement system which provides automatic next station announcements over the PA system, however this is used at the guard\’s discretion.

The SMU220s are fitted with Scharfenburg couplers and may operate with SMU200, IMU100 and IMU120 sets. They can be coupled to EMUs, but in non-revenue service only due to electrical differences.

A number of SMUs have had software upgrades which allow them to run at slightly higher speeds for services on the Gold Coast line, these units are permitted to run at 110km/h as opposed to 100km/h as normal. These units can be identified by the large letters ‘HS’ on the front of the cab indicating High Speed SMU. However due to limitations in the design, the HS designation is usually only temporarily assigned due to wheel wear problems.

Along with the SMU200s and IMU100/120s … the SMU220s are renowned for their friendlyness to passengers with disabilities (PWD). High visibility yellow doors on the outside identify the saloon doors (however on these units, the cabin doors have been painted yellow also which is bound to cause confusion) Large signage is available in the saloons for visually impaired passengers, along with the innovative use of braille signage on both the interior and exterior of the units (namely on the Door Open buttons). The Door Buttons also have audible alerts now through the use of beeps … when the doors are open, the door buttons beep regularly, and when they close they beep in quick succession. Part of the recent PWD overhaul has included the repositioning of seats in the driving cab cars to run parallel with the carriage. This has allowed space for up to 6 wheelchairs to be able to easily access the carriages … the wheelchair spaces are marked and also have folding seats. Though this sacrifices seating capacity, standing capacity is greatly increased and encourages people to move down from the vestibule.