Overall topological accessibility index (OTAI): A proposed indicator of urban transportation accessibility

The rapid and selective urbanization process leads to a series of socioeconomic and environmental problems related to urban mobility. The literature lacks a robust approach that integrates various urban mobility dimensions, as traditional methods for assessing the accessibility and connectivity of transportation networks often yield inconsistent results. In addition, the city of Viçosa (Minas Gerais, Brazil) requires a comprehensive evaluation of accessibility and connectivity in its primary and secondary road networks. To address these knowledge gaps, this study proposes and evaluates a new indicator called Overall Topological Accessibility Index (OTAI), designed to identify the most and least accessible regions of a city. This indicator combines the Connectivity Matrix, Associated Number, and Number of Indirect Links methods. To validate the proposed methodology, nine different network models were generated for Viçosa’s road system and subsequently transformed into topologically connected networks suitable for calculating connectivity and accessibility parameters. The results provided a holistic evaluation of urban accessibility and connectivity, in addition to a comprehensive analysis of the effects of various modifications to the road network, such as the implementation of ring roads. Non-central roads, network extremities, and one-way streets demonstrated low accessibility. The inclusion of a ring road resulted in a negligible improvement in the Connectivity Index of the road network but increased the OTAI of nearby roads. In conclusion, the OTAI proved to be a robust and accurate tool for a more integrated assessment of urban accessibility and connectivity, enabling targeted changes that promote transportation sustainability.