adjust_arrival_departure
                        Adjust the arrival and departure times of a
                        GTFS data
adjust_speed            Adjust the speeds of a gps-like table created
                        with 'gtfs2gps'
append_height           Add a column with height to GPS data
filter_single_trip      Filter GTFS trips in order to have one trip per
                        shape_id
filter_valid_stop_times
                        Filter GTFS data using valid stop times
gps_as_sflinestring     Converts a GPS-like data.table to a LineString
                        Simple Feature (sf) object
gps_as_sfpoints         Convert GPS-like data.table to a Simple Feature
                        points object
gtfs2gps                Convert GTFS to GPS-like data given a spatial
                        resolution
gtfs_shapes_as_sf       Convert GTFS shapes to simple feature object
gtfs_stops_as_sf        Convert GTFS stops to simple feature object
read_gtfs               Read GTFS data into a list of data.tables
remove_invalid          Remove invalid objects from GTFS data
simplify_shapes         Simplify shapes of a GTFS file
test_gtfs_freq          Test whether a GTFS feed is frequency based
write_gtfs              Write GTFS data into a zip file
