Effectively a 3-car version of the Class 317 units but used in the Glasgow area, 21 of these British Rail Mark 3-based units were built by BREL York works between 1985–1986 to replace the elderlyClass 101, Class 107, Class 120 and Class 126diesel multiple units which had worked the Glasgow South Western sector for nearly 30 years. The technical description of the units are DTSO+MSO+DTSO, consisting of a central motor car with a driving trailer at either end. The units run on the standard 25 kV ACoverhead line system, and are standard class throughout, with one toilet located in coach C. Up to four sets can be worked in multiple to form a 12-car set, although platforms are only capable of handling 8-car trains. The units have a maximum speed of, and can complete the journey between Glasgow Central and Ayr in around 52 minutes. With the introduction of the Class 334s in 2001–2002 onto Ayrshire/Inverclyde routes, both the 334s and 318s were found operating the same lines together. The 318 can also be coupled in tandem with the slightly newer Class 320 in a six car formation, which is regularly used on the North Clyde and Argyle Lines. As of January 2020, these are the oldest multiple units to be found anywhere in Scotland having been in revenue earning service for 34 years.
Accidents and incidents
In July 1995, units 318254 and 318262 were operating a Glasgow Central to Largs service when a braking system failure resulted in the train overshooting the end of the platform at Largs railway station. The train crashed through shops at the front of the station, and out into Main Street, Largs. Being very early in the morning, there were no serious injuries. The cab of vehicle 77244 needed to be completely rebuilt. 318262 managed to move by rail back to Shields depot. The reconstruction of the station building took almost ten years to complete. On 16 January 2008, number 318267 was involved in a minor collision at Glasgow Central station whilst stationary. British Rail Class 334 number 334017 was working the 08:24 passenger service from when it collided with the empty Class 318 train whilst preparing to terminate at Glasgow Central. The Class 334 train was in the process of braking and was travelling at less than when the collision occurred. Four passengers were slightly injured; however only one required hospital attention, and was transferred to Glasgow Southern General hospital in a taxi.
2005-2007 Refurbishment
Between 2005 and 2007, all Class 318s underwent a conversion process which involves the removal of the corridor connection on the driver's cars. Although one may see this as detrimental to passenger operations, there have been no great problems with the Class 334 or Class 320 units which also have no corridor connections. Apart from 'cleaning up' the appearance of the driver's cars, this allows the driver to have a far more spacious operating environment and gives the driver a better overall view. The Class 318 units were refurbished at Hunslet-Barclay. The passenger accommodation has also been improved, with new passenger door controls. The interior has been fully repainted in white, and new grab handles have been fitted. New lighting has been fitted, with similar gondolas to the Class 320 units. First ScotRail originally promised new passenger information systems, similar to those seen on other trains. In September 2008 the Scottish Government's agency Transport Scotland announced that all ScotRail trains would be eventually repainted in a new, blue livery with white Saltire markings on the carriage ends. At the same time of the announcement, the Class 318 units had been recently refurbished and repainted, so the Class 318 units would be the last in the EMU fleet to be repainted in Saltire livery. In the interim, all Class 318 units had their "SPT Rail" naming removed, leaving the units unbranded. All Class 318 units eventually received the saltire livery, and this was done while the fleet went through another refurbishment at Wabtec Doncaster between 2013 and 2017.
2013-2017 Refurbishment
The Class 318 units received another refurbishment between October 2013 and October 2017. The work includes:
Relivery into Scotrail Saltire Livery
Internal Refurbishment, including an internal repaint, new floor vinyl and new blue 'saltire' seat coverings.
Fluorescent lights replaced with LED lighting.
New floor-level lighting in the door vestibules.
Small toilet replaced with a large accessible toilet, as recently fitted to the Class 320 fleet.
Any corrosion repairs to bodywork
Unit 318251 headed south to Wabtec's Doncaster Works on 5 October 2013 and returned to Scotland on 28 March 2014. The refurbishment programme of the Class 318 fleet was completed in October 2017, with unit 318268 being the last to be completed.
