.CDP2 files are files used specifcally by 'Trainz Classics'. 'Trainz Classics' is a railroad simulation game that allows users to build and operate railroads. .CDP2 files generally contain game add-on content called "assets". "Assets" may include driver sessions, locomotive designs, rolling stock, and scenery. .CDP2 files can be imported by using the Content Manager Plus tool that is found within Trainz Classics. .CDP2 files were developed as an extension to .CDP files for adding content to Trainz Classics.