Derive trip terminals from a static GTFS feed — g2g_terminals_from

Determines the two terminals of a route from a planned (baseline) GTFS feed: the two most frequent trip endpoints (first/last stop per trip in stop_times.txt). The result feeds directly into terminals_data of g2g_extract_trips and g2g_extract_trips_and_stop_times.

Usage

g2g_terminals_from_gtfs(gtfs, route_id)

Arguments

gtfs: A GTFS feed object (named list of data.frames, as returned by gtfsio::import_gtfs() or gtfstools::read_gtfs()) or a path to a GTFS zip file (requires the 'gtfsio' package).
route_id: A single route identifier present in trips.txt. The gps2gtfs pipeline models one route (two terminals) at a time.

Value

A data.table with columns terminal_id, latitude, longitude.

Details

Frequency ranking cannot tell two ends of a line from two platforms of one place, so the function warns when fewer than 90% of trip endpoints match the two it derived (variants or branches) and when the two are close enough together to be the same physical terminal under platform-level stop_ids. Loop routes have no two terminals at all and error; use segmentation = "layover" for those.

Examples

gtfs <- list(
  trips = data.frame(trip_id = c("t1", "t2"), route_id = "r1"),
  stop_times = data.frame(
    trip_id = c("t1", "t1", "t2", "t2"),
    stop_id = c("A", "B", "B", "A"),
    stop_sequence = c(1, 2, 1, 2)
  ),
  stops = data.frame(
    stop_id = c("A", "B"),
    stop_lat = c(7.29, 7.31),
    stop_lon = c(80.63, 80.65)
  )
)
g2g_terminals_from_gtfs(gtfs, route_id = "r1")
#>    terminal_id latitude longitude
#>         <char>    <num>     <num>
#> 1:           A     7.29     80.63
#> 2:           B     7.31     80.65