This research seeks to develop the evidence base required to inform the transition towards harmonised ACL characteristics across rolling stock operating on the GB network. It will confirm and refine the previously proposed target state for ACL harmonisation (that is BS EN 50388-1:2022 without UKSNC (Umin2 = 17.5 kV)), fully accounting for technical feasibility and economic viability, and develop a detailed pathway from current to target state for existing and future rolling stock. Specifically, the research will address the following objectives: 1.Confirm and detail the target state for ACL harmonisation and the rationale for its adoption: this includes accounting for wider system consequences and trade-offs, quantified associated benefits, costs and risks. 2.Define a transition pathway from current to target state: this includes specifying the ACL changes that are technically achievable and economically justified for existing rolling stock, the ACL requirements for future rolling stock, the role and deployment of dual trains, and the phasing required to reach the target state. For more information about this opportunity, please visit the eSourcing portal at: https://www.delta-esourcing.com/tenders/UK-UK-London:-Research-services./E6E28TZ9KW To respond to this opportunity, please click here: https://www.delta-esourcing.com/respond/E6E28TZ9KW