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

Abstract

IntroductionUrban passenger mobility has undergone significant changes over the past few decades, with travel patterns becoming increasingly complex and therefore more difficult to predict and manage. Transport policy has traditionally been responsible for the management of mobility patterns. Originally, transport policy aimed at providing an answer to travel needs by offering the necessary transport infrastructure and servicesö the predict and provide paradigm. As part of the new requirements for sustainable development, there has been a general recognition of the need to manage the demand side of travel. The new predict and prevent paradigm requires a broader approach to mobility management, which clearly surpasses the boundaries of traditional transport planning.From a variety of constraints and motivations influencing travel behaviour, landuse and transport systems offer the baseline exogenous conditions steering travel patterns. Land use raises the need to move in order to participate in dispersed urban activities, while transport systems provide the conditions to satisfy these mobility needs. Other aspects, such as socioeconomic and demographic characteristics, lifestyles, cultural backgrounds, and energy issues further influence travel behaviour. Nevertheless, if the urban structure does not provide the necessary conditions to enable mobility to be sustainable, then policy actions on other fields have only limited potential. Focusing on the ability of local planning to contribute to sustainable travel behaviour, this research is centred on the land-use and transport system. Indeed, the need for the integration of land-use and transport policies has been recognised by several authors (

GIS based destination accessibility via public transit and walking in Auckland, New Zealand

“…A difference between the LUPTAI and other accessibility indices is that the outcome indices are assigned to grid cells. Silva (2008) developed the Structural Accessibility Layer (SAL), a contour measure of accessibility, which has been found to be valuable to planners (Silva and Pinho, 2010). The SAL is calculated for spatially disaggregated sub-regions defined on a case-specific basis.…”

Accessibility in Practice: 20-Minute City as a Sustainability Planning Goal

“…In recent years, accessibility research has developed measures of access to opportunities [2][3][4][5][6][7], and more cities and regions are looking to accessibility improvements as a guiding principle for transport goals. For example, Silva and Pinho [8] created a tool called the Structural Accessibility Layer (SAL) to measure accessibility considering how many, and what types, of destinations can be reached within a time budget through three different modes. Cheng et al [9] measured sustainable accessibility through the number of jobs accessible to a resident (accessibility), and how far away they are located (sustainability).…”

How does the spatial context shape conditions for car dependency? An analysis of the differences between and within regions in the Netherlands

“…In rural areas, people are sometimes totally dependent on their car while in urban areas people have more travel choices. Silva and Pinho (2010) also show that within a single urban area (Oporto), there might be big differences with regard to potential travel choices. They also make an important step in the conceptualization of the relationship between the spatial context and potential travel choice-they see travel choice and potential mobility as a feature of the combination of land use and transport features in an area, which together affect the accessibility of activities for those living there.…”

“…Stradling (2007) shows how the spatial context of rural areas leads to the car dependency of the inhabitants of these areas. Silva and Pinho (2010) show the different accessibility levels and resulting travel choices within an urban region (Oporto). A systematic identification of the features of the spatial context that determine car dependency (i.e., specific land-use and transport components) is still lacking.…”