The Structural Accessibility Layer (SAL): Revealing how Urban Structure Constrains Travel Choice

TLDR

Urban mobility problems such as congestion threaten quality of life, competitiveness, and sustainable development, prompting a need for an integrated land‑use and transport approach that uses accessibility measures to reveal mobility potential created by urban structures. This paper introduces structural accessibility and the Structural Accessibility Layer (SAL) as a planning tool, applying it to Greater Oporto to explore its potential for practice. SAL quantifies structural accessibility by comparing mode‑specific accessibility to a range of activities, and its applicability, robustness, and usefulness were evaluated by local experts. The study demonstrates SAL’s added value, providing a robust representation of mobility conditions that yields actionable insights for policy design and planning.

Abstract

Urban mobility problems, such as congestion, have been threatening the quality of life, competitiveness, and sustainable development of urban areas. The need for an integrated approach to land use and transport in mobility management has been widely recognised. Accessibility measures are believed to provide a useful framework to support this integrated approach. Some of these measures can also reveal the mobility potential created by urban structures. This paper introduces the concept of structural accessibility and a new planning tool—the Structural Accessibility Layer (SAL). This tool measures structural accessibility by comparing accessibility levels between different transport modes to a range of activities in a given territory. An application to Greater Oporto is developed in order to discuss the potential of SAL for planning practice. Results were assessed by a number of local experts discussing its applicability, robustness, and usefulness. This research produced sound evidence of the added value of the SAL in planning practice. Indeed, the SAL was found to deliver a good representation of location conditions for mobility providing interesting insights for policy design and for planning practice.