Public perspectives on the 20 mph speed reduction in Wales: A Latent Dirichlet Allocation Approach

Abstract

Introduction: This study investigates public attitudes toward the Welsh Government’s implementation of a 20 mph default speed limit on all non-unrestricted roads, for example those in urban environments, residential neighborhoods, and areas with high pedestrian activity, that previously were 30 mph, aimed at reducing traffic crashes, emissions, and improving quality of life. Method: Using a Latent Dirichlet Allocation (LDA) approach and VADER sentiment analysis to assess emotional tone, posts on X (formerly Twitter) with hashtags #20 mph and #20 mya (Welsh language for mph) were analyzed during two periods: one-month post-implementation (September–October 2023) and six months later (February–March 2024). Results: The results indicate that public opposition to the 20 mph default speed limit decreased slightly six months after its implementation but remained high. However, since opposition declined while positive sentiment increased, results suggest a positive trend, aligning with psychological theories on social influence and attitude change. Conclusions: The study underscores the value of a qualitative-quantitative approach in capturing nuanced public perspectives, offering insights beyond traditional survey methods. These findings provide actionable guidance for policymakers and practitioners seeking to implement and communicate public safety policies effectively. Practical Applications: This research uniquely contributes to the literature by examining the 20 mph speed limit in Wales, combining computational and psychological methods to explore public opinion dynamics over time.