Read a JARTIC type B traffic file — read_jartic

Reads one cross-sectional traffic volume ("type B") CSV file published by the Japan Road Traffic Information Center. The files are CP932-encoded and carry a header row; this function drops that row, supplies stable column names, parses datetime in JST, and normalizes location_name with NFKC.

Usage

read_jartic_traffic(path)

Arguments

path: Path to a raw type B file (CSV format).

Value

A data.table of 10 columns, keyed on datetime:

datetime: Observation time (POSIXct, Asia/Tokyo).
source_code: Information source code.
location_no: Observation location number.
location_name: Observation location, as from\U{2192}to.
meshcode10km: 10 km mesh code.
link_type: Link type.
link_no: Link number.
traffic: Traffic volume; missing observations are NA.
to_link_end_10m: Distance to the link end, in units of 10 m. Kept as character so that whatever the source writes – padding included – survives the read.
link_ver: Link version; NA for files published before 2018-02.

Details

The published layout has changed over time, so the header row is inspected before the file is read:

Files from 2018-02 onwards have 10 columns. Earlier files have 9 and no link_ver; for those, link_ver is filled with NA so that the returned columns are the same in either case.
A file whose first row is already an observation (no header) is read in full; the first row is not consumed as a header.
datetime is written as 2026/06/01 00:00 by most providers, but the pre-2018-02 files also use 2017/8/1 0:00:00. Both are parsed, and values that survive as NA are reported with a warning rather than passed on silently.

Bytes that are not valid CP932 cannot be decoded and leave NA in location_name. That is reported with a warning too, because the rest of the row still looks intact.

Examples

read_jartic_traffic(
  system.file("dummy", "type_b.csv", package = "jarticr")
)
#> Key: <datetime>
#>               datetime source_code location_no    location_name meshcode10km
#>                 <POSc>      <char>       <int>           <char>       <char>
#> 1: 2022-11-01 00:00:00          36           1  徳島駅前→県庁前       513376
#> 2: 2022-11-01 00:00:00          36           2 APAホテル前→南口       513376
#> 3: 2022-11-01 01:00:00          36           1  徳島駅前→県庁前       513376
#> 4: 2022-11-01 01:00:00          36           2 APAホテル前→南口       513376
#>    link_type link_no traffic to_link_end_10m link_ver
#>        <int>   <int>   <int>          <char>    <int>
#> 1:         1     101     120            0050   202200
#> 2:         1     102      45            0120   202200
#> 3:         1     101      80            0050   202200
#> 4:         1     102      NA            0120   202200