49 CFR 633.13: Initiation of project management oversight services.

Project management oversight services will be initiated as soon as practicable, once the Administrator determines that this part applies. In most cases, this means that project management oversight will begin during the project development phase of the project, generally after the locally preferred alternative has been chosen (if applicable), unless the Administrator determines it more appropriate to begin oversight during another phase of the project, to maximize the transportation benefits and cost savings associated with project management oversight.