Defining Sufficient Accessibility: Integrating Measured and Perceived Transportation Access with Quality-of-Life Outcomes

Sufficient accessibility means that all individuals have a minimum level of access to essential opportunities such as work, school, healthcare, and leisure, making it possible to meet their basic needs. In this study, we integrate “measured accessibility” and “perceived accessibility” within a quality-of-life (QoL) framework to empirically determine what constitutes “sufficient” accessibility. Using community survey data from Austin, Texas, we combine a composite accessibility index—built from both primal (cumulative opportunity) and dual (minimum cost) measures across auto and transit modes—with self-reported QoL and perceived accessibility. We develop a sufficiency threshold by identifying the level of perceived accessibility associated with median QoL under different levels of measured accessibility. Our results indicate that perceived accessibility is a stronger predictor of QoL than measured access. A sufficiency threshold is derived using a normative regression-based approach, identifying the minimum perceived accessibility score required to reach the median QoL benchmark under typical access conditions. Logistic regression analyses further reveal that women, renters, long-term residents, and full-time workers are significantly less likely to report sufficient perceived accessibility—suggesting that social and structural barriers persist even in areas with good physical access. The study underscores the importance of integrating user- and system-level indicators into transport equity analyses. Policy applications include using sufficiency thresholds to evaluate whether new investments help lift disadvantaged groups out of accessibility poverty and enable more equitable QoL outcomes.