Developing a Cycling Crash Risk Module for the Health Economic Assessment Tool

Abstract

Active travel, namely cycling and walking, leads to health benefits that can be quantified and monetized based on epidemiological and economic evidence. In order to support decision-makers, practitioners and researchers in carrying out such calculations the World Health Organisation created the Health and Economic Assessment Tools for walking and cycling (HEAT) in 2007. HEAT aims to provide scientifically robust results at low complexity for users. The current version of HEAT considers effects of physical activity and (soon) air pollution, but not crash risk, one of the three main health impact pathways for active travel. This study develops a crash risk module for cycling to be integrated in HEAT. Based on reviews of previous health impact studies, the HEAT crash module will apply a basic approach, which assesses crash risk as a function of (1) a default background national or municipal crash rate comprising a measure of traffic casualties as numerator (e.g. number of fatalities, injuries or crashes among cyclists) and a measure of exposure as denominator (e.g. distance or time cycled) as well as (2) the observed exposure in the case study. A systematic data review was carried out to identify available data on crash rates. Starting from international databases that include national and municipal data, the search will be expanded by reviewing national and municipal reports on safety and, separately, travel surveys to obtain exposure estimates. For before and after assessments of changes over time a non-linear “safety-in-numbers/numbers-in-safety” adjustment will be applied. Existing international databases containing crash rates mainly use population as measure of exposure, which is inadequate for health impact modeling. Cycled distance or time requires consultation of national and municipal sources. We anticipate obtaining such data from a majority of large western European countries, the United States, as well as selected major cities. The presented crash risk module will complement the scope of HEAT without compromising its simplicity. The module is initially limited to certain countries and municipalities and not suitable for use-cases at a smaller scale, i.e. project assessments. It may be further developed as follow: (1) The module could be used other countries and municipalities by adding a modifier of the crash rate that takes into account local particularities defined by the tool user. (2) The module could be used to evaluate specific cycling projects by including adjustment options for effects of local determinants of cycling safety.