transport_model {gtfs2emis}

Transport model

Description

This function converts a public transport data set in GTFS format into a GPS-like table with the space-time positions and speeds of public transport vehicles. The function also allow users to set the spatial resolution of the output and to adjust the speed of public transport vehicles given a min_speed and max_speed range.

Usage

transport_model(
  gtfs_data,
  min_speed = 2,
  max_speed = 80,
  new_speed = NULL,
  parallel = TRUE,
  ncores = NULL,
  spatial_resolution = 100,
  output_path = NULL,
  continue = FALSE
)

Arguments

gtfs_data

A path to a GTFS file or a GTFS data organized as a list of data.tables created with gtfstools::read_gtfs().

min_speed

numeric (in km/h) or a speed units value. Minimum speed to be considered as valid. Values below minimum speed will be updated according to the new_speed parameter, which can affect the arrival and departure times of vehicles at transit stops. Defaults to 2 km/h.

max_speed

numeric (in km/h) or a speed units value. Maximum speed to be considered as valid. Values above maximum speed will be updated according to the new_speed parameter, which can affect the arrival and departure times of vehicles at transit stops. Defaults to 80 km/h.

new_speed

numeric (in km/h) or a speed units value. Speed value used to replace the speeds that fall outside the min_speed and max_speed range or which are missing from the GTFS input. When new_speed = NULL (the default), the function uses the average speed of the entire GTFS data feed.

parallel

logical. Decides whether the function should run in parallel. Defaults is TRUE.

ncores

integer. Number of cores to be used in parallel execution. This argument is ignored if parallel is FALSE. Default (NULL) selects the total number of available cores minus one.

spatial_resolution

The spatial resolution in meters. Defaults to 100. The function only creates points in order to guarantee that the minimum distance between two consecutive points will be at most the spatial_resolution value. If a given GTFS shape_id has two consecutive points with a distance smaller than the spatial resolution, the algorithm will not remove such points.

output_path

character. A directory path. If NULL (Default), the function returns the output. If the user passes a valid passed, the output will be saved in the output_path dir. Note that that the output of each public transport shape_id is saved separately in different files. Setting an output_path is recommended when working with large public transport system because the output of the function can be significantly large.

continue

logical. Argument that can be used only with output_path When TRUE, it skips processing the shape identifiers that were already saved into files. It is useful to continue processing a GTFS file that was stopped for some reason. Default value is FALSE.

Value

A ⁠data.table sf_linestring⁠ object or NULL.

See Also

Other Core function: emission_model()

Examples

library(gtfs2emis)
library(gtfstools)

# read GTFS
gtfs_file <- system.file("extdata/bra_cur_gtfs.zip", package = "gtfs2emis")
gtfs <- gtfstools::read_gtfs(gtfs_file) 

# keep a single trip_id to speed up this example
gtfs_small <- gtfstools::filter_by_trip_id(gtfs, trip_id ="4451136")
  
# run transport model
tp_model <- transport_model(gtfs_data = gtfs_small,
                            min_speed = 2,
                            max_speed = 80,
                            new_speed = 20,
                            spatial_resolution = 100,
                            parallel = FALSE)