match_tag: Match STATS19 collisions with TAG (RAS4001) cost estimates

In stats19: Work with Open Road Traffic Casualty Data from Great Britain

Match STATS19 collisions with TAG (RAS4001) cost estimates

Description

Downloads and processes the UK Department for Transport TAG Data Book table RAS4001, and joins estimated collision costs to STATS19 data.

Three matching modes are available:

• "severity" — cost varies only by collision severity

• "severity_road" — cost varies by severity and road type

• "severity_road_bua" — cost varies by severity & road type, where road type is determined using ONS Built-Up Area (BUA) polygons (2022)

BUA polygons are downloaded automatically from: https://open-geography-portalx-ons.hub.arcgis.com/api/download/v1/items/ad30b234308f4b02b4bb9b0f4766f7bb/geoPackage?layers=0

Optionally, total costs may be summarised by severity and/or road type.

Usage

match_tag(
  crashes,
  shapes_url =
    paste0("https://open-geography-portalx-ons.hub.arcgis.com/api/download/v1/",
    "items/ad30b234308f4b02b4bb9b0f4766f7bb/geoPackage?layers=0"),
  costs_url = paste0("https://assets.publishing.service.gov.uk/media/",
    "68d421cc275fc9339a248c8e/ras4001.ods"),
  match_with = "severity",
  include_motorway_bua = FALSE,
  summarise = FALSE
)

Arguments

crashes	A STATS19 collision data frame. May be sf or non-sf, but spatial geometry is required when using "severity_road_bua".
shapes_url	URL to download the ONS Built-Up Areas geopackage. Defaults to the official ONS 2022 dataset.
costs_url	URL to download the TAG Data Book RAS4001 table (ODS format). Defaults to the Department for Transport asset link.
match_with	Character string specifying the matching mode. One of: "severity" "severity_road" "severity_road_bua" The default uses match_with = c("severity", "severity_road", "severity_road_bua"), so users get tab-completion and help in RStudio.
include_motorway_bua	Logical; if TRUE, motorways inside a built-up area polygon are treated as "built_up" rather than "Motorway".
summarise	Logical; if TRUE, returns a summary table of total costs (in millions) grouped by severity and/or road type.

Details

The function:

1. Downloads and parses RAS4001 cost tables

2. Computes road type using STATS19 fields or optional BUA polygons

3. Joins appropriate cost estimates

4. Optionally aggregates totals

When crashes is an sf object and summarise = TRUE, geometry is automatically dropped.

Value

A data frame (or sf object if input is sf) with added columns for estimated collision costs. If summarise = TRUE, a summary table of total costs (in millions) is returned.

Examples

## Not run: 
  # Simple severity-based matching
  match_tag(stats19_df, match_with = "severity")

  # Severity + road type
  match_tag(stats19_df, match_with = "severity_road")

  # Using ONS Built-Up Areas, with motorway override
  match_tag(
    stats19_df,
    match_with = "severity_road_bua",
    include_motorway_bua = TRUE
  )

  # Summarised totals
  match_tag(stats19_df, match_with = "severity", summarise = TRUE)

## End(Not run)

stats19 documentation built on March 18, 2026, 5:08 p.m.