Is there an emotional dimension to road safety? A spatial analysis for traffic crashes considering streetscape perception and built environment

Modern streetview image data provide two types of valuable information: the objective built environment and humans’ subjective perception of the streetscape. In the road safety domain, the built environment has been identified as playing a significant role while indicators of human perception are commonly used to evaluate street quality in urban planning. However, studies examining the association between humans’ perceptions of the streetscape and traffic crashes remain limited. This study aims to address this question and to inform safety considerations at the micro level in the planning process for the targeted streets. To answer the question, this study integrates databases on motor vehicle crashes, points of interest, street view images, and road networks for the urban area of Daejeon city in South Korea in 2019. A deep learning model was employed to calculate six perceptual indicators–wealthy, lively, boring, depressing, safety, and beautiful–based on a crowdsourcing dataset. Furthermore, a Bayesian multivariate Poisson-lognormal model with spatial-varying coefficients was introduced to simultaneously account for spatial random effect and the shared unobserved effect across crash severity levels. Results indicate that four of the six perceptual variables significantly affect the number of slight injury crashes, showing spatially heterogeneous effects. Based on the values of human perception indicators and their impacts on traffic crashes, we identified road segments which need special attention to objective safety performance when considering street renovation. Additionally, built environment factors such as the proportion of vegetation, the presence of sidewalks and fences, and points of interest (including educational, health service, and commercial establishments) were found to reduce the number of motor vehicle crashes. Overall, the findings are expected to facilitate the safety-enhanced street planning project, and contribute to the development of human-centric cities.