Economic BCAs are typically handled by large eng firms like Arup, Jacobs, and WSP. However, the tricky task of modeling time savings (given that transport systems are complex) is often subcontracted to more specialized firms such as Steer.
Deloitte, KPMG, etc are usually more involved in writing the financial case (how to fund the project).
Deloitte, KPMG, etc are usually more involved in writing the financial case (how to fund the project).