use of diesel fuel for traction by 2035. The project was initially handled primarily by a workgroup at the University of St Andrews, before a request for tenders was issued in September 2020 seeking a commercial partner for the full design, installation, and demonstration of a hydrogen fuel system using the Class 314 unit. In December 2020 the unit was moved to the Bo'ness and Kinneil Railway, near Falkirk, for conversion work to begin. The lead contractor for the conversion work was rolling stock refurbishment firm Brodie Engineering, with Arcola Energy acting as hydrogen energy specialists. Arcola's A-Drive fuel cell powertrain forms the core of the new traction system, with hydrogen tanks and battery modules installed underneath all three vehicles. The increased weight of the new components was carefully measured and controlled in order to avoid exceeding the unit's maximum permissible axle load and to reduce the likelihood of the unit's kinematic envelope increasing; it was partially offset by replacing the original traction motors with new alternating current models. The intent is for the demonstrator to remain reasonably similar to a "standard" Class 314 unit, so that it can be run under its existing certificates of conformity for the general railway network. In September 2020, it was announced that the demonstrator would appear at the COP26 Climate Change Summit, to be held in Glasgow during November 2021. The unit was to operate special services for the benefit of visiting delegates. In advance of the summit the unit was reclassified into the alternative-fuels class number range and renumbered 614209. An acknowledged limitation of the Class 614 demonstrator is that it can only carry of hydrogen, pressurised at . This is sufficient for short-distance operation as a prototype, but storage capacity will need to be significantly increased for normal passenger service to be feasible. The project team claim that it will be possible to achieve this increase by installing additional storage tanks within the vehiclesa necessity as the UK's standard loading gauge does not allow enough space for roof-mounted tanks. Accidents and incidents On 21 July 1991, unit 314203 was damaged in the Newton rail accident. The leading DMSO vehicle was destroyed, but later replaced with the BDMSO vehicle from written-off unit 507022. The repaired unit re-entered service in May 1996. On 12 December 1994, units 314208 and 314212 were severely damaged when they were caught in floodwaters in the low-level platforms