The units were built to replace elderly Class 117, Class 119 and Class 121 "Heritage" DMUs, and locomotive-hauled trains on services from London Paddington along the Great Western Main Line. The trains were designed as a faster, air conditioned variant of the Class 165 Turbo, intended for longer distance services, and, like the 165s, belong to the Networker family of trains. They were originally known as Networker Turbos to distinguish them from the electrically propelled members of that family.
These units are a modification of the Class 165 design. They have a top speed of 90 mph (145 km/h) (suitable for mainline use), are carpeted throughout and have air-conditioning. Externally, the class 166 can be distinguished from a Class 165 by having a first class section at each end of the train, and opening hoppers on every other window.
- Network SouthEast (with "Turbo Express" route branding)
- Thames Turbo
- First Great Western 'Dynamic Line'
The London to Brighton add=on also includes a 166 in First Great Western 'Dynamic Lines' livery.
|166/2||DMCO - MSO - DMCO||166201 - 166221|
Although texture files for the Class 166's destination boards exist, inputting them in-game does nothing, perhaps owing to limitations at the time.