SNCF's BB 25500 class are part of a series of electric locomotives built by Alsthom. They are the dual system version of the BB 17000 (AC) and BB 8500 (DC) locomotives (17000+8500=25500). They are fitted with monomotor bogies with two different gear ratios. This allows them to have either increased tractive effort for freight, or a higher top speed. This makes them suitable for both freight and passenger trains. They were built in three distinct batches leading to detail differences. They remain in use as mixed traffic locomotives, mostly with TER and Transilien.