Development of an objectively measured walkability index for the Netherlands

Abstract

Background: Walkability indices have been developed and linked to behavioural and health outcomes elsewhere in the world, but not comprehensively for Europe. We aimed to 1) develop a theory-based and evidence-informed Dutch walkability index, 2) examine its cross-sectional associations with total and purpose-specific walking behaviours of adults across socioeconomic (SES) and urbanisation strata, 3) explore which walkability components drive these associations.

Methods: Components of the index included: population density, retail and service density, land use mix, street connectivity, green space, sidewalk density and public transport density. Each of the seven components was calculated for three Euclidean buffers: 150 m, 500 m and 1000 m around every 6-digit postal code location and for every administrative neighbourhood in GIS. Componential z-scores were averaged, and final indices normalized between 0 and 100. Data on self-reported demographic characteristics and walking behaviours of 16,055 adult respondents (aged 18-65) were extracted from the Dutch National Travel Survey 2017. Using Tobit regression modelling adjusted for individual- and household-level confounders, we assessed the associations between walkability and minutes walking in total, for non-discretionary and discretionary purposes. By assessing the attenuation in associations between partial indices and walking outcomes, we identified which of the seven components drive these associations. We also tested for effect modification by urbanization degree, SES, age and sex.

Results: In fully adjusted models, a 10% increase in walkability was associated with a maximum increase of 8.5 min of total walking per day (95%CI: 7.1-9.9). This association was consistent across buffer sizes and purposes of walking. Public transport density was driving the index's association with walking outcomes. Stratified results showed that associations with minutes of non-discretionary walking were stronger in rural compared to very urban areas, in neighbourhoods with low SES compared to high SES, and in middle-aged (36-49 years) compared to young (18-35 years old) and older adults (50-65 years old).

Conclusions: The walkability index was cross-sectionally associated with Dutch adult's walking behaviours, indicating its validity for further use in research.

Keywords: Built environment; Physical activity; Transport; Validation; Walkability.

Fig. 1

Walkability index map 150 m buffer size for the Netherlands (top left), the densely populated region of Randstad (top right) and the city of Amsterdam (bottom). Walkability is scaled from 0 to 100 where red denotes the 10% lowest walkability scores, and green denotes the 10% highest walkability scores

Fig. 2

Pearson correlation matrix for walkability components of 150 m buffer for all PC6 addresses in the Netherlands. The top part of the matrix denotes the absolute value of correlation and significance levels (*** denotes p-value < 0.001, ** for p-value < 0.01). The bottom half denotes bivariate scatterplots between two corresponding variables with a fitted line showing direction of correlation. pd18_150z: population density, rs15_150z: retail & service destination density, gs15_150z: green space, lm15_150z: land use mix, sw19_150z: sidewalk density, pt18_150z: public transport density, sc19_150z street connectivity, walk18_pc6_150: walkability index