As well as converting to GTFS UK2GTFS has functions for manipulating GTFS files.

Reading and Writing

gtfs_read

gtfs_write

Cleaning and Validating GFTS

gtfs_clean() Clean simple errors from GTFS files

gtfs_compress() Reduce file size of a GTFS object

gtfs_fast_trips() Find fast trips

gtfs_validate_internal() Validate a GTFS object (in R)

Manupulating GTFS

gtfs_merge() merge a list of gtfs files

gtfs_split() Split a GTFS object

gtfs_split_ids() Split a GTFS object based on trip_ids

gtfs_clip() Clip a GTFS object to a geographical area