As set out in the Transport Decarbonisation Plan, published in July 2021, the government’s ambition is to remove all diesel-only trains from the network by 2040, and the department remains committed to this ambition. A number of train operators, such as Northern and Chiltern, are currently undertaking procurement processes to replace diesel-only trains with an aim to reduce carbon emissions and improve the passenger experience. As of October 2023, there are approximately 2,900 diesel-only vehicles operating on the network out of a fleet of over 15,000 vehicles. Since October 2020, over 200 diesel-only vehicles have been removed from passenger operation.