Measuring the effect of vehicle safety on road traffic crash severity in Iran: using structural equation modeling

Abstract

Objective: Vehicle safety plays a key role in reducing the number of road traffic deaths and serious injuries. This study aims to investigate the effect of vehicle safety on the severity of traffic crashes in Iran using structural equation modeling (SEM). Methods: This was a comparative cross-sectional study of all imported vehicles with Aras free trade zone license plate as well as all domestic vehicles (cars produced in Iran) commuting on Tabriz-Jolfa road. The study population included drivers who had accidents on Tabriz-Jolfa road over a period of one year from September 22, 2020 to September 21, 2021 and were injured or  their vehicles had been damaged (n=652). Data was collected using set of questionnaires with 10 sections. The effect of independent variables, as exogenous latent variables (human, vehicle, and environmental factors), on a dependent variable, as an endogenous latent variable (crash severity) was measured using SEM. All data were analyzed using Mplus 8.0 software. Results: In the structure part of the model with foreign vehicles group, the effect sizes of three exogenous variables, i.e., human, environmental, and vehicle factors, on the dependent variables were found to be 0.412, 0.396 and 0.358, respectively. The effect sizes in the model with domestic vehicles were found to be 0.312, 0.702 and 0.820, respectively.   Conclusion: Vehicle factors (variables related to car safety) had a high impact on crash severity in the national license plate and domestically manufactured vehicle group, indicating the necessity of improving vehicle safety.