British Rail Class 166

The British Rail Class 166 Turbo Express is a fleet of diesel multiple units (DMUs), originally specified by and built for British Rail, the then United Kingdom state owned railway operator. They were built by ABB at York Works between 1992 and 1993. 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.

The class is still in service, and is operated by First Great Western on its services out of London Paddington station. The trains, along with that operator's Class 165 trains, are often known as Thames Turbos.

Description
These units are a modification of the Class 165 design. They have a top speed of 90 mph (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.

Other differences over a 165 are as follows:
 * Air conditioning
 * Two toilets (a 165 only has one toilet per unit)
 * Tables in first class and in one third of the middle carriage
 * Dedicated cycle/luggage storage in the middle carriage
 * Different interior panelling between the door and seating areas
 * Grab rails painted in yellow instead of the blue (unrefurbished) and the red (refurbished) found in the 165s

Twenty-one 3-car units were built, numbered 166201-221. Each unit was formed of two outer driving motors, and an intermediate motor. The technical description of the formation is DMCL+MS+DMCL. Individual carriages are numbered as follows:
 * 58101-58121 - DMCO
 * 58601-58621 - MSO
 * 58122-58142 - DMCO

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.

Six cars were added to the original order in 1991 after Network SouthEast acquired some of the Cotswold Line line services from Regional Railways to allow Class 158 units to be converted to Class 159s for the West of England services.

Class 166 units were some of the first trains in Britain to be designed for Driver Only Operation, in cases were a Guard is required they must carry out their door operation duties via a bell system to signal the Drivers to close doors and start the train. This requires the Guard to return to a vacant cab at each station to carry out these duties, examples of this First Great Western services on the Cotswolds Line.

Operations
When built, these units were operated by the Thames Line and North Downs Line subdivisions of Network SouthEast and therefore carried NSE blue, red and white livery with Turbo Express branding between the two first class windows of the DMCL carriages.

Their main destinations included fast-trains to Reading, Newbury and Oxford, with some services continuing beyond Oxford to Banbury and Stratford-upon-Avon, or along the Cotswold Line to Evesham, Worcester, Great Malvern and Hereford. Units are also used on the Reading to Gatwick Airport services along the North Downs Line. Many services operated by the 166 were branded as Turbo Express in the timetables.

In future it has been proposed to run the Class 166 along with the Class 165 units on the Cardiff to Portsmouth route, subject to line clearance. They will still run on the Oxford-Great Mavern-Hereford line too.

Following privatisation, the units passed to the Thames Trains franchise, who introduced a new blue, white and green livery. There were two variants of this livery; the Class 166 units had the 'express' variant.

In April 2004, operation of the Thames Trains franchise passed to the First Group, who now operate the company as First Great Western. The livery remained the same, but FGW Link branding was applied over the obsolete Thames Trains logo.

London and Thames Valley Refresh
Towards the end of January 2010, First Great Western have announced an £8,000,000 refresh programme to their fleet of Class 166 Turbo DMU trains. The carpets & seats will be retrimmed, interiors repainted, Passenger Information Displays replaced with a GPS based system and toilets upgraded. The refresh work is being carried out in house at Reading Depot, with the first two vehicles already arrived and eventually five vehicles will be in the works at any one time. The refresh will be completed by the end of March 2012, by which time 151 vehicles (Class 165 as well as Class 166) will have received the refresh work.