A railway company has revealed why a batch of innovative locomotives that were once a rarity in West Yorkshire have become a frequent visitor to local rails in recent months.

Class 69 diesel engines, which were converted into modern freight locomotives from out-of-use Class 56s, have been a regular sight in places like Mirfield, Huddersfield and Marsden since around Christmas time.

In April 2019, GB Railfreight (GBRf) announced that several ageing locomotives would be rebuilt as Class 69s by Progress Rail at its Longport facility.

Seen as a cheaper option than importing new locomotives, the rebuild scheme involved the replacement of the original Ruston-Paxman RK3 engine with the EMD 710 powerplant, with the locos being equipped with newer electronic control systems.

Since their gradual introduction, the Class 69s have been used most frequently in the south of England, including on engineering trains around Tonbridge, Kent.

In recent months, their almost daily appearances in West Yorkshire has had rail enthusiasts speculating. Several examples of the Class have been observed running light engine between Doncaster and Marsden, near Huddersfield.

Now, a spokesperson for GBRf has revealed why the locos have become commonplace in these parts, with route learning for drivers being the motivation.

"It's road learning for ballast trains, and it was just that the 69 was spare, so this was not for a new freight flow," the spokesperson said.

With intense work on the Transpennine Route Upgrade due to take place over the coming months and years, it seems likely that future ballast trains would be related to the major track-works needed for that project.