routes regularly. The remaining 32 units were refurbished by Alstom Eastleigh during 2002–2005. They received new interiors, CCTV, light clusters dot matrix displays and the 2+3 seating was replaced with 2+2 seats. Unit 507033 was the last Merseyside set to be refurbished, entering service having been named Cllr George Howard in August 2005. Incidents Unit 507022 was written off as a result of a serious collision with unit 507004 at Kirkdale TMD on 30 September 1991. Driving motor 64388 is now in unit 507004, as the latter's was damaged beyond repair, and the other motor carriage, renumbered, went to Glasgow-based 314203. Collisions with buffer stops at terminal stations have also occurred. Sets 507029 and 507032 both received damage due to overrunning at Kirkby in 1991 and 1997 respectively. Set 507019 was involved in a collision at West Kirby on 11 January 2007, and carriage 64423 had to be sent to Crewe Works for repair. On 30 June 2009, unit 507002 without a driver rolled out of Kirkdale TMD, derailing at a set of points further down. The incident, which caused disruption to many services, was caused by failure to apply the brakes, whilst maintenance was performed so that when isolating wooden paddles were removed from between the conductor rail and pick-up shoes, the train moved off without a driver on board. On 23 May 2011, it was announced by the Office of Rail Regulation that Merseyrail were fined £85,000 and ordered to pay legal costs of £20,970.15 due to the breach of the Health and Safety at Work etc. Act 1974 leading to this incident. On 13 March 2021, unit 507006 formed part of a passenger train which overran the buffer stop and derailed at Kirkby railway station. Twelve people sustained minor injuries. This unit was sent to Newport for disposal. Description Class 507 units are formed of three cars, and numbered 507001 to 507033. Original plans were drawn up for 47; later 38 Class 507 units to be built, but costs enforced a reduction in the number. Sets are made up of two driving motor cars ('A' DMSO with the compressor; 'B' BDMSO with the battery) and a trailer. Car numbering is as follows: 64367-64399 - DMSO (Driving Motor Second Open) 71342-71374 - TSO (Trailer Second Open) 64405-64437 - BDMSO (Battery Driving Motor Second Open) Originally, each three-car set seated 234 passengers, this figure being reduced to 222 following