Mapping Urban Accessibility in Data Scarce Contexts Using Space Syntax and Location-Based Methods

Abstract

Data scarcity is still a common barrier to adequately understanding urban access in Global South countries. Widely used location-based methods address the traditional definition of accessibility as the easiness to reach land-uses by means of available mobility modes. Space Syntax instead analyses accessibility as network centrality focusing only on the topological and geometric properties of urban layouts, making it comparatively less data-intense. However, the interpretation of its outputs is limited to its own theory. Knowledge is missing on how such metrics are comparable to the metrics produced by location-based methods. The objective of the research was to compare both approaches for mapping urban accessibility in two cities in Guatemala. Our hypothesis tested the assumption that Space Syntax metrics could consistently reflect accessibility conditions that so far have only been measured by location-based methods. We proposed an approach using volunteered geo-information and produced accessibility maps following both approaches that were then compared using Pearson correlations. Space Syntax metrics at low and high radii are consistently correlated with location-based access to land uses that reflect location quality at neighbourhood and city-wide scale correspondingly. Space Syntax metrics at lower radii reflect time-based access restrictions either posed in the location-based analyses or by reduced accessibility by public transport. The hypothesis acceptance, p < 0.01, expands the scope of accessibility knowledge derivable from limited data availability using Space Syntax, which is relevant for its applicability in data-scarce contexts by planners and researchers in the Global South. Rather than replacing location-based methods Space Syntax offers an important complementary measure to geographical accessibility. This having been said, Space Syntax could contribute to early-stage planning by gaining overall insights into patterns of urban access.

Modelling residential land values using geographic and geometric accessibility in Guatemala City

“…Accessibility metrics were mostly produced in previous work and are aggregated in a hexagonal tessellation (Morales et al, 2016). The size of the hexagons (300 m innerdiameter) provided an adequate resolution at an affordable computational demand.…”

Predictive land value modelling in Guatemala City using a geostatistical approach and Space Syntax

“…The data set was available from recent research conducted in the study area by (Morales et al 2017a(Morales et al , 2017b. The data consists of 1,169 observation points of residential land value appraisals and a hexagonal tessellation of the city urban area (Figure 1).…”

“…Geographic-access and geometric via geographic access are both expressed as indexes from 0 (low access) to 1 (high access) and are based on the individual metrics per mobility mode. More details about the computation of the access metrics and indexes are found in published literature (Morales et al 2017a(Morales et al , 2017b.…”

“…Most expensive land is observed at the core matching the CBD where various types of commerce and office buildings concentrate (area '1'). As discussed by Morales et al 2017a andMorales et al 2017b, the CBD benefits the most from geographic-access to several facilities, as well as from geometric-access and geometric via geographic access. This explains why the highest land values can be expected in this area, even though few observations were available there.…”

“…Under spatialized modelling conditions and variable selection, geometric via geographic access has a greater impact in explaining land value than the CBD access metric. By observing the model coefficients and in order to facilitate some visual understanding we included in Annex A the visualizations of the following metrics: geometric via geographic-access, CBD access, banks and restaurants, and jobs (Morales et al 2017a(Morales et al , 2017b. CBD access only reflects generalized concentric patterns of travel times to an assumed focal point.…”