‘Food Deserts’ Theory Applied in the Field of Road Safety: Testing the Impact of Traffic Analysis Zone Size in Cape Town

Abstract

Motivated by the extremely high road fatality rates in South Africa (Vanderschuren et al., 2017), the authors are on a quest to improve road safety analysis methodologies, adapting the “Desert theory (Wrigley et al., 2002; Hulchanski, 2010; Vanderschuren et al., 2021). ‘Food Deserts’, as an example, are places where people, without access to motorised transport, are compelled to shop at corner stores with exorbitant costs and less fresh products. In line with the ‘Desert’ theory, a Z-value calculation is conducted. Z-values are numerical measurements used in statistics to determine a value relationship to the average of a group, measured in terms of standard deviations from the mean (Heyes, 2019). Z-values are calculated per Traffic Analysis Zone (TAZ). Vanderschuren and Newlands (2024) have proven that an adaptation of the ‘Food Desert’ theory to the field of road safety is possible. In this work, the authors use smaller TAZs (52 instead of 16). This study revealed that the Z-value range for 52 TAZs is larger than the range for 16 areas. Furthermore, a significant number of large TAZs show variation within the area. More importantly, in some cases, a risk or desert area turns into a low road safety risk area. This underpins the need for small TAZs, and more detailed results.