삼중차분법을 이용한 바닥형 보행신호등 보조장치의 보행 안전 개선효과 분석

This study examines the impact of a floor-type pedestrian signal assist device on pedestrian traffic safety in Seoul using the Difference-in-Difference-in-Differences(DDD) method. Furthermore, it aims to identify whether the effects of these devices differ between daytime and nighttime, with the goal of enhancing their practical effectiveness and contributing to the improvement of pedestrian environments. In light of growing concerns about “Smombie” (smartphone+ zombie)—pedestrians distracted by smartphone use—these devices have been introduced to improve pedestrian safety. However, empirical studies on their actual effectiveness in reducing pedestrian accidents remain limited. The study covers the periods from 2015 to 2017 (pre-installation) and from 2021 to 2023 (post-installation), with the unit of analysis set at 100-meter grid cells across Seoul. First, Propensity Score Matching was conducted to select comparable treatment and control groups and to confirm the parallel trends assumption. Subsequently, the difference-in-difference-in-differences method was applied to estimate the policy effect. The results show that the installation of floor-type pedestrian signal assist devices did not have a significant impact on reducing pedestrian accidents during the daytime. However, during nighttime, the devices were associated with a statistically significant decrease in accidents, suggesting a time-specific policy effect. This study contributes to the literature by providing empirical evidence on the effectiveness of floor-type pedestrian signal assist devices, offering policy implications for enhancing pedestrian safety.