f cost estimation methods is provided in the UK Department for Transport's Transport Analysis Guidance (TAG). The framework estimates costs and benefits by comparing two scenarios: a "without-scheme" scenario, which represents how the transport system would evolve if the proposed intervention is not implemented, and a "with-scheme" scenario, which reflects conditions after the intervention is introduced. Cost estimation focuses on the difference between these two scenarios, ensuring that only the incremental impacts of the policy or project are captured rather than overall system costs.[16]The framework requires that costs be assessed over a long-term ap

3.2.1. Step 1: Define the market clearlyDefining market comprises of:Identifying the good or service involved.Identifying who the buyers and sellers are. Asking whether there are other people or groups affected by the transaction, even if they are not directly buying or selling.