The British Rail Class 508 (or 4PER) electric multiple-unit (EMU) passenger trains were built by British Rail Engineering Limited, at Holgate Road carriage works in 1979–80. They were the fourth variant of BR's standard 1972 design for suburban EMUs, eventually encompassing 755 vehicles and five classes (313/314/315/507/508). They have mostly worked on the Merseyrail network since 1983, and continue to do so, now refurbished by Alstom's Eastleigh Works. The Class 508 unit is now 42 years old, making them among the third oldest units still in service on the UK mainland rail network, after the Class 313 and Class 507.