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 extensively operated by Great Western Railway 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 opening hoppers on every other window. Until late 2013 the presence of first class at each end was another distinguishing feature.

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

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 DMCO+MSO+DMSL. Individual carriages are numbered as follows:
 * 58101-58121 - DMCO
 * 58601-58621 - MSO
 * 58122-58142 - DMSL changed from DMCO in 2013

One driving vehicle of 166209 had serious fire damage, as a result of the Betchworth train fire. During this period, the centre coach 58609 intercepted the middle of 165128 and the unaffected driving vehicle was out of service in Reading Train Care Depot. However, as of 21st May 2016, it was put back in service following repairs for 6 months long.

The units were built to replace elderly Class 117, Class 119 and Class 121 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 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 where 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 Great Western Railway services on the Cotswold 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.

A rail user's group has suggested that Class 165 Turbo and the express variant, Class 166 Turbo Express will work services on the Cardiff Central to Portsmouth Harbour route after the Thames line cascade, subject to line clearance. However, a Network Rail document released in 2011 cast doubts on whether this would actually happen after revealing the gauge between Cardiff and Portsmouth is currently not suitable for Class 166s.

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 Great Western Link, and subsequently to First Great Western. The livery remained the same initially, but FGW Link branding was applied over the obsolete Thames Trains logo.

In 2012, First Great Western took delivery of five Class 180 Adelante units for Cotswold Line services, and three-car Sprinter units for Reading to Basingstoke Line services, allowing Class 165 and 166 units to be used to be used entirely for Thames Valley services.

London and Thames Valley Refresh
Towards the end of January 2010, First Great Western announced an £8,000,000 refresh programme to their fleet of Class 166 Turbo DMU trains. The carpets & seats were retrimmed, interiors repainted, Passenger Information Displays replaced with a GPS based system and toilets upgraded. The refresh work was carried out at Reading Depot. All 151 vehicles have now been refurbished.

2014/15 Refresh
Since late 2014, First Great Western have started another set of refreshes to the Class 166 fleet. They are progressively being fitted with LED head/tail lights, a new, dark green GWR livery, new toilets which are more accessible than the old toilets, new door buttons which are significantly easier to push than the original buttons, and new door buzzers. All units have now received the refresh. Unit 166204 was named in honour of Twyford Stationmaster Norman Topsom MBE who retired in November 2015, 166205 received a GWR interior and 166201-203, 166207, 166209, 166211, 166215 and 166221 were painted in an all over blue livery.

The changes made during the 2010 refresh remain in place, however the units will all be receiving new 2+2 seating, for use on longer distance services such as Bristol to Weymouth once the fleet are cascaded to the Bristol area.