[<< wikibooks] Trainz/references/Filename character restrictions
Filename syntaxes (or name formation) in Trainz assets are heavily restricted for compatibility reasons. As filenames are not displayed to end-users, there is no need for localization support (File and directory paths) or other format class characters.

Specifically, filenames within Trainz must obey the following rules:

Filenames must not begin with a space (' '), a period ('.'), or a tilde ('~').
Filenames must be at least one character long.
Filenames must not end with a space (' ').
Filenames should be kept to a reasonable length. No fixed length is currently enforced, however if compatibility issues arise at a later date N3V Games may add length limits.
Smart quotes, accents, umlauts and other non-ASCII characters are disallowed.
Filenames must consist of the following ASCII characters only: