Mapping liveability: The “15-min city” concept for car-dependent districts in Auckland, New Zealand

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Applied Geography 163 (2024) 103197

Mapping liveability: The “ 15-min city ” concept for car-dependent districts in Auckland, New Zealand

Jing Jiang

^*

, Weijie Qiao , I-Ting Chuang , Yan Li , Tianyi Wang , Lee Beattie

Architecture and Planning at the University of Auckland, Auckland, New Zealand

A R T I C L E I N F O Handling Editor: Dr. Y.D. Wei Keywords:

15-Min city Living local Proximity

Micro mobile-urbanism Liveable area

A B S T R A C T

This research explores the feasibility of aligning cities with post-COVID realities by retrofitting the emerging 15- min city model into the current urban setup. COVID-19’s lasting global effects on trans-territorial mobility, particularly in car-dependent cities, prompt a rethinking of urban models and infrastructure for heightened resilience and post-pandemic liveability. Using network analysis and GIS mapping techniques, this research applies the 15-min city model to identify the most “liveable areas” in two car-dependent suburban neighbourhoods with contrasting service structures—dispersed in Remuera and centralised in Onehunga in Auckland City, New Zealand. “Liveable areas” are defined as areas with overlap coverage of all 6 essential services within a 15- min walk. The analysis involves a horizontal comparison of essential service coverage and a longitudinal analysis of the impacts of essential service coverage, both collectively and individually, within both neighbourhoods.

Findings suggest the potential to retrofit both districts’ urban infrastructure, while proximity to retail, healthcare, and leisure facilities are the services most urgently needing improvements. Noted issues include excessive big-box retail growth, uneven healthcare distribution, and private, non-everyday access to natural resources. This research methodically tests proximity-based planning for sustainable living, work, and recreation in car- dependent districts with centralised or dispersed urban structures.

1. Introduction

Moreno’s (2021) 15-min city concept emphasises proximity and diversity as key features of liveability in urban planning based on walking and cycling. Taking typical car-dependent districts in Auckland, New Zealand, as an example, this study uses diverse analytical methods to measure the feasibility of applying the 15-min city framework to assess and improve the spatial impact of car-dependent urban structure on liveability. The study’s objective is to quantify the liveability of the current urban structure by measuring the diversity and accessibility of each essential service under the 15-min city framework. Our goal is to expand the potential of the application of the 15-min city concept in retrofitting into the current urban setup. Additionally, we propose a quantitative method to support evidence-based, actionable strategies for transforming existing urban landscapes into 15-min cities in the future.

The COVID-19 pandemic has prompted a re-evaluation of urban living conditions and accelerated changes in daily travel behaviour. The most affected are those without cars in cities dependent on automotive transport, especially when public services like buses and trains are

suspended during crises. Such disruptions highlight the global need to prioritise walkable access to daily services. The 15-min city offers a solution by focusing on the spatial arrangement and accessibility of urban resources (de Valderrama, Luque-Valdivia, &

Aseguinolaza-Braga, 2020; Balletto et al., 2021). It ensures that residents can reach essential services such as grocery stores, workplaces, healthcare, education, and leisure within a 15-min walk or cycle (Mor- eno et al., 2021). Beyond mere proximity, the concept also incorporates density and diversity as key criteria for evaluating the effectiveness of urban service provision, offering new perspectives for post-pandemic living. Numerous studies have underscored the resemblance between the 15-min city approach and the well-established planning model of the 1920s, namely Perry’s neighbourhood units (Khavarian-Garmsir et al., 2023). This reveals that the idea is less an innovation than a practical application of enduring planning principles (Pozoukidou & Chat- ziyiannaki, 2021). However, the focus on spatial proximity has drawn criticism for its potential to inadvertently foster negative consequences such as segregation and isolation of neighbourhoods, particularly affecting socioeconomically disadvantaged communities (Abbiasov

* Corresponding author. School of Architecture and Planning, The University of Auckland, 26 Symonds Steet, Auckland Central, Auckland, 1010, New Zealand.

E-mail address: [email protected] (J. Jiang).

Contents lists available at ScienceDirect

Applied Geography

journal homepage: www.elsevier.com/locate/apgeog

https://doi.org/10.1016/j.apgeog.2024.103197

Received 31 August 2023; Received in revised form 19 December 2023; Accepted 6 January 2024

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et al., 2022). Nevertheless, amidst navigating the post-COVID-19 pandemic landscape, the notion of the 15-min city—a self-contained neighbourhood model that is less susceptible to the disruptions of mobility—has gained renewed attention in creating urban environments better equipped to meet future challenges (de Valderrama et al., 2020).

Although the theoretical framework of the 15-min city concept has been well-defined, there is a recognised gap in research concerning its practical application, adaptation, and alignment to the unique characteristics of different urban environments (Khavarian-Garmsir et al., 2023). The current concept by Moreno et al. (2021) prioritises the establishment of a comprehensive and flexible framework based on the understanding that “within the 15-min radius, a city can incorporate all basic essentials.” Some studies thus begin from a centre or a cluster (Gaglione, 2021; Nowor´ol et al., 2022), while a few take the opposite perspective. Moreover, the 15-min city concept emphasises the comprehensive benefit of all basic services rather than the difference among individual services (Khavarian-Garmsir et al., 2023; Pozoukidou

& Chatziyiannaki, 2021).

Two significant gaps are thus identified: the absence of quantitative methods to empirically apply and adapt the 15-min city concept to specific urban contexts and the need for measuring the varying impacts of different amenities in retrofitting the 15-min city framework. To address these gaps, the study proposes two main research questions: 1) How can the liveability of the current urban structure be quantified through the lens of the 15-min city concept? 2) How can the spatial impacts of varying services under the 15-min city concept be measured and actionable strategies developed?

To address these questions, we use typical Auckland suburban neighbourhoods as case studies underpinned by two empirical objectives. The first empirical objective is to evaluate the level of compliance of these neighbourhoods with the criteria of the 15-min city through the mapping of “liveable areas”. The second empirical objective is to measure the hierarchical influences of varying essential services considered in the mapping of the “liveable areas”. “Liveable areas” are defined as

zones where residents can access 6 essential services within a 15-min walking radius, thereby providing convenient access to daily neces- sities, services, and recreational facilities. The essential services under consideration include healthcare services such as pharmacies, clinics, and hospitals; supermarkets and grocery stores; food and beverage

(F&B) establishments; educational institutions; open green spaces; and

public transit stations (Gaglione, 2021; Nowor´ol et al., 2022). We have deliberately excluded workplaces from the list of essential services. This decision acknowledges the evolving work landscape in the sharing economy and the post-pandemic era, where flexible and remote work options have gained social acceptance (Di Marino et al., 2023). More- over, commuting distances between work and home are influenced by a range of factors. For example, household income levels can affect commuting choices, with high-income and low-income households often selecting different residential locations (Surprenant-Legault &

EI-Geneidy, 2010). Additionally, the availability of transportation infrastructure and amenities near workplaces can further influence these distances (Guti´errez-i-Puigarnau et al., 2016). Consequently, we argue that although including workplaces within walkable distances aligns with sustainable urban models, the logistical constraints of reconfigur- ing existing urban layouts make this a challenging, if not unlikely, goal to achieve.

In this study, we concentrate on the neighbourhoods of Remuera and Onehunga in Auckland, each exemplifying distinct urban structures, to evaluate liveable areas and assess the impact of different services (Fig. 1). Remuera is characterised by an affluent, dispersed urban layout that was originally designed with a car-centric approach. This results in an uneven and sparse distribution of essential services, posing challenges for those reliant on walking for social or economic reasons and indirectly encouraging an unhealthy lifestyle. On the other hand, One- hunga presents a more mixed-use, compact urban framework, inte- grating residential and light-industrial areas along with a commercial hub near the port. Although Onehunga benefits from a more advanta- geous spatial pattern of service distribution, it still faces issues of car

Fig. 1.Location context of case studies.

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dependency.

To better understand these nuances, we turn to advanced analytical tools. Utilising GIS-based techniques, we visualise areas within both neighbourhoods that meet the 15-min city criteria and employ a one- factor-at-a-time (OFAT) analysis (Daniel, 1973) to assess the individual impact of each essential service on liveable areas, where only one service is omitted at one time while the other services are kept fixed. Through this multi-layered approach, we aim to provide new insights into how the liveability of areas can be influenced by their differing urban structures. More significantly, our study aims to demonstrate that each neighbourhood, despite its inherent challenges, offers unique opportunities for enhancing liveability and connectivity.

The contribution of this research is twofold. First, the findings enrich the theoretical understanding of the 15-min city concept, particularly regarding the impact of individual service categories. Second, the empirical analysis uncovers both challenges and opportunities for Auckland in adopting the 15-min city model, offering insights into its transformative potential for future urban planning initiatives.

2. Literature review

2.1. From a car-dependent city to a 15 minute-city

The development of a car-dependent city represents a negative effect of urban sprawl. The highway construction in the 1960s led to cars becoming the dominant travel mode, providing convenience and flexi- bility to move in cities. Gradually, cars replace trams, and in peri-urban areas, public transportation has become supplementary to cars (New- man et al., 2016). However, this shift to car-centric transport has brought about issues like congestion and air pollution. Furthermore, the continuing decrease in active travel modes that are beneficial to public health compounds the challenge. To counteract these detrimental effects, a reimagining of urban transport and infrastructure is imperative.

Drawing on the emerging discourse of Chrono-urbanism, the concept of the 15-min city has been developed as a counter-narrative to car- dependent urban sprawl (Moreno et al., 2021). Proposed in 2016 (Moreno, 2016), this innovative urban model aligns with Goals 3, 9, 11, and 13 of the United Nations’ 2030 Sustainable Development Agenda (Resolution, 2015) and emphasises pedestrian-friendly, proximity-orientated urban planning. The applicability of this model extends beyond theoretical bounds, as evidenced by initiatives taken up by cities around the world. For instance, Melbourne in Australia introduced a 20-min neighbourhood plan to establish living areas where essential services are easily accessible within a short distance (Thornton et al., 2022). Simi- larly, Portland and Detroit, United States, have promoted their 20-min neighbourhood to build a safe and walkable neighbourhood to meet the daily needs of people (Portland City Bureau of Planning and Sus- tainability, 2012). Other urban development plans include Barcelona’s superblocks and Ottawa’s 15-min neighbourhood, highlighting the prevalence of the 15-min city concept as a sustainable paradigm for urban development (C40 City of Portland Bureau of Planning and Sus- tainability, 2012). Considering the concept of a 15-min city and the plans proposed in other cities, it is evident that the 15-min timeframe is not a rigid measure of proximity efficiency. Instead, the core idea is to explore a proximity-orientated urban model that facilitates easy access to essential services within an X-minute walk or riding distance (Logan et al., 2022).

Building on this framework, a growing body of literature has further contextualised and assessed the 15-min city concept. Its principles have evolved into a guiding paradigm for urban restructuring, with a focus on reducing commuter times (Khavarian-Garmsir et al., 2023). Recent empirical studies in Portland, Melbourne, and Paris indicate that the 15-min city concept is more than a one-size-fits-all model but rather adapts to local cultural contexts (Pozoukidou & Chatziyiannaki, 2021).

This empirical analysis has mapped and visualised how the concept in- tegrates within cities. For example, the study by Bartzokas-Tsiompras

and Bakogiannis (2023) constructed a 15-min walking city index to assess the accessibility of walking of 7 essential services in 121 European urban areas and discovered the need for more concentrated and efficient land use planning and transportation improvements. In addition, other studies measuring proximity to essential services through overlapping areas in Naples and London highlighted the impact of different urban morphological attributes and population densities on the spatial distribution of a 15-min catchment, providing insights into the governance of urban transformation (Gaglione, 2021). These studies aim to guide and provide principles for optimising the spatial form and layout of cities.

Generally, cities apply the 15-min city concept as a framework for developing new urban districts. However, reconfiguration of existing urban structures and forms poses a significant challenge, particularly from an economic perspective. Targeted strategies require further investigation to improve proximity within the existing urban environment.

2.2. Key attributes of the 15-minute city: accessibility, proximity, and diversity

Accessibility is a key indicator for measuring the ease of reaching opportunities, contributing to sustainable urban development. The 15- min city concept further emphasises enhancing proximity, which encompasses physical distance to services and the temporal dimension (time required) that allows residents to reach them via non-vehicle modes (Moreno et al., 2021). Prior studies have interpreted the efficiency and effectiveness that proximity can bring to residents’ daily lives (Schindler et al., 2022). In the context of a 15-min city, diversity refers to the categories of services that meet residents’ needs. To study these factors, scholars have applied a range of data-driven methodologies, including the NExt proXimity Index (NEXI) (Olivari et al., 2023) and Geographic Information Systems (GIS) techniques. For example, Service Area and O-D Cost Matrix algorithms within Network Analyst tools in ArcGIS were implied to investigate accessibility to urban facilities (Bhuiya et al., 2023; Ferrer-Ortiz et al., 2022; Korah, Nunbogu, &

Ahmed, 2023). In addition, an isometric analysis focused on the performance of these services was conducted using GIS by Abdelfattah et al.

(2022), considering different walking buffers ranging from 300 to 900 m. While existing studies generally approach the 15-min city as an integrated area, they often overlook the nuanced roles played by different types of services. For instance, Nowor´ol et al. (2022) conducted a study in Krakow focusing on both a “minimal” and an “optimal” version of proximity, shedding light on different variants of geographical accessibility. Other studies have targeted specific types of services, such as grocery store accessibility across different age groups in Vancouver (Hosford et al., 2022), healthcare service accessibility in Beijing (Zheng, 2023), and 20-min city for the ageing group in Liverpool (Dunning et al., 2023). Despite these various angles of inquiry, there remains a limited empirical understanding of the hierarchical influence of different services on the concept of a 15-min city. This gap offers an opportunity for more nuanced research, particularly regarding the primary, secondary, and tertiary influences of these services on resource allocation within 15-min cities (Pozoukidou & Angelidou, 2022).

3. Methodology 3.1. Study area

This study focuses on two neighbourhoods—Remuera and One- hunga—that serve as distinct representations of urban models in Auckland. Remuera, an affluent suburb in East Auckland, boasts a rich history as a key M¯aori settlement dating back to the 18th century. Over the years, it has evolved into a traditional suburban area, characterised by large mansions, small farms, and commercial developments. Local amenities are clustered in two separate zones along a significant arterial

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road, while smaller corner stores are dispersed among the residential areas. In contrast, Onehunga, situated in South Auckland, represents a more recent urban development model. Originally a commercial port, it later morphed into a light industrial zone with a compact urban layout.

Onehunga Mall Road connects the primary commercial and service areas of the district, addressing the essential needs of the local populace.

Unlike Remuera, Onehunga features a dominant centre that affects distinct travel patterns.

3.2. Data source and analyses

To understand what the 15-min city concept would look like in spatial terms in two car-centric neighbourhoods with distinct urban layouts, we utilised data from Google Maps for essential services and Open Street Map for street network geo-information specific to Remuera and Onehunga. To collect relevant Points of Interest (POIs), a Python script leveraging the Google Maps Place API (Application Programming Interface) was employed. This script successfully collected a total of 516 valid POIs across the two designated districts.

Each gathered POI underwent a rigorous validation process to ensure both accuracy and reliability. This involved re-entering each POI into Google Maps for a thorough assessment and cross-referencing against the original data. The validation stage included a comparison of features, types, and geographic details of the downloaded POIs against the information available on Google Maps. Invalid data entries were promptly identified and removed. Additionally, POIs with discrepancies in geo-information were manually corrected to align with the accurate geographic details provided by Google Maps. For the street networks of Remuera and Onehunga, geo-information was downloaded using the

OSMnx package, sourced from OpenStreetMap (Boeing, 2017).

In terms of data analysis, we leveraged the capabilities of Geopandas and the OSMnx package within the Python programming environment (Jordahl et al., 2020), operating specifically within the ArcGIS-Pro framework. The analysis encompasses an assessment of travel speeds based on data culled from the New Zealand Household Travel Survey and the 2022 Rider Report. Following the data collection phase, comprehensive cleaning, merging, and visualisation tasks were executed using ArcGIS software.

All the collected data were subsequently imported into ArcGIS, a comprehensive geospatial analysis platform, for consolidation, visualisation, and more nuanced analysis. To tackle challenges associated with the precision of geo-information and to mitigate privacy concerns, this study employs hexagonal grids measuring 100m ×100m as the foun- dational units for analysis (Shoman et al., 2019). These grid units are used for visualising the analysis findings as heat maps, providing insights into the spatial distributions of the six essential services across the two studied districts.

The data analysis is structured into two main components. Initially, we map the 15-min liveable areas within Remuera and Onehunga, considering the six essential services. The second component employs a one-factor-at-a-time (OFAT) experimentation approach to investigate the impact of each service on the 15-min liveable zones. Each identified area is juxtaposed against the original 15-min liveable regions, facili- tating a comprehensive examination of the impact of each omitted service. The research design is visually represented in Fig. 2.

Fig. 2. Research design diagram.

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3.3. Mapping the liveable area

The liveable area in this study is defined as the region where all 6 essential services overlap. It is visualised by generating a 15-min walking catchment area, employing a combination of Geopandas and the OSMnx package within Python, and integrated with ArcGIS-Pro software. The mapping process occurs in stages. First, the 15-min walking catchments for each Point of Interest (POI) within the 6 services are plotted. Next, the catchment areas of POIs representing the same service are merged to establish the accessible zone specific to that service. Finally, the catchment areas for all 6 services are overlaid, and the area common to all is delineated as the liveable area in the context of this study. We hypothesise that variations in urban structures and the spatial distribution of services will result in differing extents of liveable areas.

3.4. One-factor-at-a-time (OFAT) experimentation

In addition to mapping the liveable areas, this study also employs a one-factor-at-a-time (OFAT) experiment to assess the impact of individual services on the extent of these areas. Specifically, each of the 6 essential services is systematically omitted in turn, creating a modified 15-min catchment area that encompasses only the remaining 5 services.

By comparing these altered 15-min areas to the original liveable areas covering all 6 services, we are able to quantify the discrepancies in area coverage attributable to the absence of a specific service. A larger difference in area indicates a more significant impact of the omitted service on the liveable area, which in turn provides insights into the challenges of “retrofitting” the 15-min city concept to accommodate the absence of that particular service. Updated maps are generated using the same methodology as the initial mapping process, and the results are further organised and visualised through GIS-based analyses.

4. Results

4.1. The quantification of liveability: the spatial distribution of the 15- minute liveable areas

By mapping the liveable areas in Remuera and Onehunga, this part demonstrates the empirical result of our quantification of liveability through the lens of the 15-min city. The visualisation of the liveable areas in Remuera and Onehunga reveals contrasting results as shown in Fig. 3. The spatial distribution of the 15-min liveable area in Remuera is linear and dispersed, covering 38% of the locality. Conversely, the liveable area in Onehunga is notably dense and concentrated, covering approximately 70% of the area.

In Fig. 3a, the liveable area in Remuera is demarcated by black lines, and the 6 essential services are mapped in various colours. This liveable extends in a relatively linear pattern along the road network, covering an approximate area of 4.13 km²(38% of the total area of Remuera).

Specifically, it spans central-east Remuera, stretching east-west along Remuera Road and Benson Road and north-south along Victoria Avenue and Orakei Road. The essential services appear dispersed along the roads, with transportation services having the highest number of locations and grocery stores having the least, with only 5 locations. The distribution of the transit stations is relatively even, covering both central and marginal parts of Remuera. Grocery stores, education and

F&B are more concentrated along the main arterial on Remuera Road.

Healthcare and leisure services are mainly found in the outskirts.

Notably, this liveable area in Remuera encompasses 54.3% of transit stations, 59.3% of educational facilities, 71.6% of F&B establishments, 54.5% of healthcare services, and 80% of grocery stores.

In Fig. 3b, Onehunga’s liveable area is clearly concentrated around two central hubs and spans an estimated 5.26 km²(74% of Onehunga’s total area). It stretches along a southwest-northeast axis, notably around the Waitangi Road and the intersection of Onehunga Mall Road and

Church Road. The 6 essential services display a more compact distribution pattern, with F&B services having the most locations and healthcare services the fewest, with only 12 locations. Except for leisure facilities, which are mainly in the outskirts, the other services are highly concentrated around Onehunga Mall. Impressively, the liveable area in Onehunga includes 94.2% of transit stations, 91.7% of educational facilities, 89.2% of F&B services, and 100% of both healthcare services and grocery stores.

4.2. The measurement of the spatial impact of each essential service of liveable areas

By conducting OFAT experiments, this part demonstrates our measurement of the spatial impacts of varying services under the 15-min city model. The OFAT experiment’s findings offer nuanced understandings of how each service affects the extent of liveable areas. While existing studies have established the importance of essential services, the quantifiable impact of various services on liveability remains underex- plored (Pozoukidou & Angelidou, 2022; Pozoukidou & Chatziyiannaki, 2021). This insight serves as a crucial element for shaping data-driven strategies geared towards neighbourhood improvements and promot- ing sustainability.

4.2.1. Impact of each essential service

Our analysis reveals that F&B services, transit stations, and education services generally exert a minor influence on liveable areas in both Remuera and Onehunga. In contrast, grocery stores, healthcare services, and leisure facilities have a more pronounced impact.

Figs. 4 and 5 illustrate the OFAT outcomes in Remuera and One- hunga, respectively. In each figure, the original liveable areas are outlined in black, while the revised areas are shaded. These shaded regions depict the spatial changes caused by omitting a particular service. A larger divergence in these regions underscores the greater significance of the omitted service, thus identifying the potential for “retrofitting”

the 15-min city model to the existing urban fabric. In other words, when a particular service is omitted and results in a larger liveable area, it implies that the service itself restricts the liveable area. Therefore, if this service is more strategically located, the liveable area can be expanded to all.

Fig. 4 shows that in Remuera, the hierarchy of the impact of the 6 essential services from low to high is transit stations, education services,

F&B (Food and Beverage) services, leisure services, healthcare services,

and grocery stores. It can be seen that the impacts of the first 3 services are relatively small and homogeneous, with almost no new coverage area generated beyond the 15-min liveable area after deduction.

Notably, the last three services exhibit more pronounced changes in their coverage areas when removed. Specifically, excluding leisure services results in a new area of 0.15 km²in Remuera’s southwestern corner. Likewise, removing healthcare services adds an area of 0.58 km² to the northern enclave. The omission of grocery stores has the most substantial impact, increasing the catchment area by 4.08 km², which now covers around 70% of the whole Remuera neighbourhoods.

For Onehunga, Fig. 5 illustrates a similar ranking of essential service impacts, from lowest to highest, as follows: transit stations, F&B services, educational services, leisure facilities, grocery stores, and healthcare services. The impacts of the first 3 services are also relatively small and homogeneous, resulting in almost no new area generated. The latter 3 services show more significant changes in their coverage areas when omitted. For example, removing leisure and grocery services results in new areas of 1.33 km²and 1.68 km², respectively. The omission of healthcare services has the most considerable impact, dramatically expanding the catchment by 2.48 km²to cover nearly 85% of the total Onehunga neighbourhood.

4.2.2. Impact of the top 3 most essential services

Our OFAT analysis for Remuera and Onehunga pinpoints the

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Fig. 3.The characteristics of the 15-min liveable areas of Remuera and Onehunga.

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essential services with the most considerable influence on liveable areas.

Specifically, leisure, healthcare, and grocery stores stand out as the most impactful services in Remuera. In Onehunga, it’s leisure, grocery stores, and healthcare services. These areas, showing different impacts, are

potential zones for conversion into more liveable spaces with improved connectivity. This also suggests avenues to leverage advancements in active mobility technology, like e-scooters and e-bikes, for better alignment with the 15-min city framework. We illustrate these areas by Fig. 4.15-minute areas with one type of service omitted in Remuera.

Fig. 5.15-minute areas with one type of service omitted in Onehunga.

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mapping the 15-min catchments, excluding the three most crucial services, in both locations.

In Fig. 6, the grey zone (labelled “a”) and the pink zone (labelled “b”) represent the 15-min catchments in Remuera that omit the least and most impactful three services, respectively. Compared to Remuera’s 15- min liveable area outlined in black, the grey zone barely extends the coverage, while the pink zone enlarges by approximately 129%, covering 89% of Remuera’s total area. The areas not covered primarily surround the eastern Remuera Golf Club.

Similarly, in Onehunga, the grey area (labelled “c”) and the blue area (labelled “d”) in Fig. 6 demonstrate the 15-min catchments after excluding the least and most impactful three services, respectively.

Relative to the black-outlined 15-min liveable area in Onehunga, the grey zone remains virtually unchanged, while the blue zone grows by about 41%, covering 86% of Onehunga’s entire area. The zones not covered are primarily the western neighbourhoods and south-eastern industrial parts of Onehunga.

The OFAT analysis has substantively identified leisure, healthcare, and grocery stores as key levers for redefining the liveable areas in both Remuera and Onehunga. These services stand as crucial benchmarks for the future design and planning of 15-min liveable areas. The nuanced understanding of these influential services enables us to conceive more targeted and efficient urban development strategies.

4.3. Towards actionable strategies: micro-mobility vs. walkability The findings suggest there may be opportunities for developing actionable strategies in urban planning, especially within the context of the 15-min city framework. As touched upon in the literature review, the 15-min city is not only about distance, but rather about the time needed to access essential services. This could mean that areas currently outside

a 15-min walking radius for accessing essential services might still be reachable through other active modes of transport. Given technological advancements in e-mobility, this area warrants further exploration.

Our analysis indicates that both Remuera and Onehunga could potentially be adapted to better align with the 15-min city model, particularly by focusing on optimising the most impactful essential services. This offers a possible avenue to examine alternative transportation methods, such as e-mobility, in greater detail. Recognising the potential of e-scooters and e-bikes, we have looked into how these forms of micro-mobility might improve daily accessibility to essential services in these neighbourhoods, thereby more closely aligning them with the 15-min city concept. To gain some insights into this, we have visualised and compared 15-min areas that are walkable—omitting the top three most impactful services—with those that could be covered using e- scooters and e-bikes in Remuera and Onehunga. Preliminary observations, as shown in Fig. 7, suggest that these micro-mobility options might be able to cover a significant portion of these neighbourhoods, supporting their possible future transition into 15-min liveable areas.

Firstly, our observations in Remuera and Onehunga suggest that the boundaries of areas accessible by micro-mobility are relatively smooth and consistently expand, particularly when transitioning from e-scooters to e-bikes. This contrasts with the boundaries of walking-accessible areas, which exhibit more irregular features, such as niches and con- caves—areas that are not easily reachable by foot. These irregularities in the walkable areas may largely be attributed to limitations in street connectivity, particularly at the edges.

In addition, Fig. 7 uses a gradient from dark to light to sequentially map the liveable areas within 15 min of e-scooter and e-bike travel in both neighbourhoods. In Remuera, e-scooters and e-bikes significantly expand the liveable area, covering 82% and 96% of Remuera, respectively. Using e-scooter travel, almost the entire central part of Remuera,

Fig. 6. Comparative 15-min areas with different services omitted.

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from south to north, becomes a part of the liveable area, along with the east and west parts, except for the Remuera golf course. In comparison with the 15-min walking areas that omit the three most impactful services, 75% and 93% are respectively included in the e-scooter and e- biking liveable areas. These proportions rise when focusing solely on Remuera, to about 86% and 100%, respectively.

The situation in Onehunga appears to be even more promising.

Although the 15-min walking areas, minus the three most impactful services, cover approximately 86% of the total territory, the scope for e- scooter and e-bike accessible areas is broader, covering 96% and nearly 100% of the area. The e-bike mode of travel allows almost all of One- hunga, except for its south-eastern corner, to be included in the liveable area. When compared to the 15-min walking area that omits the three most impactful services, it’s covered 100% by e-scooter-accessible areas.

Finally, the diagram indicates that the 15-min e-scooter accessible areas in Remuera and Onehunga are interconnected. However, it’s worth noting that e-bike-accessible areas share an overlapping region that covers over 2.54 km². Therefore, it is evident that e-mobility can sufficiently support the expansion of liveable areas. This transformation has the potential to convert neighbourhoods that have 50% of essential services accessible by walking into areas that are 100% accessible, particularly when facilitated by e-mobility options like e-scooters and e- bikes.

5. Discussion and conclusions

Achieving sustainable urban design is more straightforward when we can measure progress and evaluate potential interventions. The 15-min city concept, as proposed by Moreno et al. (2021), offers one such quantifiable framework for reimagining urban landscapes to heighten proximity and diversity. Taking two distinct Auckland City neighbourhoods, Remuera and Onehunga, as an example, our study evaluates the concept. Specifically, we investigate how these services impact the

liveability of these areas within the 15-min city construct. Through a comprehensive methodology that involved mapping 15-min walking areas around 6 essential services: grocery stores, healthcare services, transit stations, leisure activities, F&B, and educational institutions, we identified liveable areas. These are pocket zones where residents can access all these services within a 15-min walk.

After that, our one-factor-at-a-time (OFAT) analysis adds a further layer of complexity, measuring and highlighting the unique role each essential service plays in shaping the scope of these liveable areas. This is consistent with Logan et al. (2022), which cautions that prioritising certain services could inadvertently overlook other crucial yet under- stated amenities. Our study highlights the importance of various essential services to the liveability of a district, which includes not only the quantity of the services but also the evenness of their spatial distribution. Our analysis shows that an increase in the quantity of services contributes to the expansion of the liveable areas, and within the existing urban framework, the spatial evenness or lack thereof in the distribution of these services can also considerably alter the scope and overlap of liveable areas. Our OFAT analysis enables us to pinpoint areas requiring relatively low investment for substantial impact, as it distinctly illustrates the potential for optimising the expansion of the liveable areas by adjusting the spatial distribution of the 3 most essential services in both Remuera and Onehunga. The focus here lies not just on identifying current liveability conditions but also in suggesting avenues for future research that can provide targeted improvement strategies.

In addition, our findings suggest that the 15-min city concept is not merely aspirational but serves as a practical tool for fostering more active modes of transportation like walking and cycling. This aligns with broader objectives of sustainability, such as lowering transportation emissions (IEA, 2020) and improving public health and social cohesion (Dempsey et al., 2011; Mueller et al., 2020). Our study illuminates the limitations and varied effectiveness of micro-mobility solutions.

Although in areas like Remuera, where existing urban structures Fig. 7. Comparative area of potential 15-min liveable areas via micro-mobility in Remuera and Onehunga.

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necessitate more comprehensive solutions, our study confirms that micro-mobility has great potential to improve daily accessibility to essential services in dispersed or compact urban structure, thereby more closely aligning them with the 15-min city concept.

Ultimately, our study contributes to the literature on sustainable urban planning, offering actionable insights into the complexities of urban liveability. We propose a quantitative method for quantifying the liveability of the current urban layouts and measuring the shortfalls of accessibility of each essential service under the 15-min city framework, which provides actionable strategies in other regions and cities. These contributions collectively work towards the overarching goal of creating self-sufficient, resilient neighbourhoods that provide residents with safe, convenient access to their daily needs (Moreno et al., 2021), even in the face of unforeseen disruptions like the COVID-19 pandemic.

5.1. The divergent performance of 15-minute liveable areas of Remuera and Onehunga

The study shows clear differences in access to essential services between Remuera and Onehunga. Generally, Remuera lags Onehunga in accessibility, largely due to its low-density residential layout. Although the primary focus of this study is on essential service accessibility, it’s important to acknowledge the role residential density plays in creating walkable neighbourhoods (Fan et al., 2018). This contrast is highlighted when examining the size and population of the liveable areas in each neighbourhood. For example, Remuera’s liveable area spans 3.36 km², slightly larger than Onehunga’s 3.16 km². However, less than half (46%) of Remuera’s residential area falls within this zone, compared to nearly all (92%) of Onehunga’s residential areas. Additionally, only 3643 residents, or about 36.9% of Remuera’s total population, live within this liveable area, while Onehunga accommodates 5678 residents—approximately 90% of its total population—within its corresponding zone. In this context, Onehunga not only provides better accessibility to essential services but is also more conducive to walkability.

Interestingly, Remuera’s low-density residential layout provides greater opportunities for “retrofitting” under the 15-min city framework. Our study indicates that approximately 80.4% of Remuera’s demarcated liveable area is zoned residential, contrasting sharply with Onehunga’s 48.4%, which incorporates industrial and commercial zones as well. Moreno et al. (2021) emphasise the importance of achieving

“optimal density” for comprehensive sustainability, encompassing economic, social, and environmental factors. Although Onehunga currently excels in essential service accessibility due to its high-density,

“concentrated” urban structure, our OFAT analysis indicates a limited scope for expanding the liveable area by adding individual services.

Essentially, to notably improve the liveable area in Onehunga, multiple essential services would need to be introduced simultaneously at a new location. On the flip side, Remuera’s low-density but primarily residential layout offers the potential to elevate both its density and diversity to optimal levels. This is supported by our OFAT findings, which suggest that Remuera’s liveable area could significantly expand if specific services were added or if mobility options were optimised. Thus, the contrasting performances of Remuera and Onehunga underscore the necessity for the adoption of context-specific strategies that consider the distinct urban fabric of each area.

5.2. Gaps in “retrofitting” the 15-minute city in Remuera and Onehunga Elaborating on the notion of context-specific strategies introduced earlier, this section further implements the OFAT analysis to assess the impact of various services on the scope of 15-min liveable areas in Remuera and Onehunga. These findings indicate that leisure facilities, grocery stores, and healthcare services significantly influence the extent of these liveable zones. This aligns with previous research conducted in the USA and New Zealand (Logan et al., 2022). Specific services,

particularly grocery stores and healthcare, emerge as the most influential indicators affecting liveable areas in both neighbourhoods, exerting a greater impact than the other services examined. This means that improvements to the current spatial distributions of these two services would greatly expand the current scope of the liveable areas. On the other hand, transit stations—primarily bus stations in this context—though frequently populated for convenience and requiring minimal economic investment for the establishment, exert a limited influence on the scope of liveable areas. This observation corroborates Logan et al. (2022), who argue that the effectiveness of the 15-min city metric is influenced by the density of services.

The limited availability and variety of grocery stores and healthcare services in Remuera and Onehunga can be traced back to the travel, living, and consumption habits dictated by their existing urban frame- works. To illustrate, Remuera has only 5 counted grocery stores, primarily consisting of suburban shopping malls and big-box retail stores.

Numerous studies have highlighted the adverse effects of big-box retail on smaller stores and local shopping streets (Haltiwanger et al., 2010).

In line with this, our study affirms that big-box retail hampers the effective “retrofitting” of the 15-min city, as it opposes the objectives of fostering closeness and building compact, mixed-use neighbourhoods (Moura et al., 2017). Generally situated on the city’s outskirts to mini- mise capital costs, big-box stores cater to a large consumer base, encouraging car usage and undermining localised living and consumption patterns (Pozoukidou & Angelidou, 2022). The retrofitting process aspires to convert these single-purpose locales into diverse, human-scaled spaces where more people can reside near essential services (C40 City of Portland Bureau of Planning and Sustainability, 2012). The OFAT analysis helps to pinpoint the potential areas that can yield maximum benefits if accessibility is improved, thereby informing strategies for the most efficient allocation of resources. These findings set the stage for exploring alternative mobility solutions that could further refine our understanding of liveable urban spaces.

5.3. The potential and advantages of micro-mobility in improving walking accessibility

Building on insights from the OFAT analysis, we investigate the role of micro-mobility—specifically e-scooters and e-bikes—as a promising solution for enhancing liveability in car-dependent urban areas. As illustrated in Fig. 7, the expanded boundaries accessible via micro- mobility notably support the liveable areas impacted by the top three essential services. These findings suggest that despite the structural limitations of Remuera and Onehunga, micro-mobility could serve as a feasible strategy for transforming these neighbourhoods. This is consistent with previous studies advocating for pedestrian and micro- mobility options (Papas et al., 2023) and aligns with research conducted in Europe (Abdelfattah et al., 2022). Notably, the OFAT analysis enabled us to pinpoint areas that would yield significant benefits with minimal resource investment. For instance, the north-eastern section of Remuera displayed a greater need for improved connectivity to facilitate active transportation options. Based on this data, strategies can be more precisely targeted to these areas. Introducing e-mobility infrastructure, such as cycling lanes or e-mobility sharing hubs, could efficiently and effectively encourage increased usage in these targeted zones.

Additionally, the data suggests a notable potential for micro-mobility to enhance trans-territorial transportation. This is evidenced by the overlapping 15-min e-biking zones in Remuera and Onehunga, a finding that is consistent with existing research on the future applications of micro-mobility in urban settings (Dia, 2019). However, it’s important to note that the utility of micro-mobility in achieving the 15-min city concept is not uniform across different areas. In Remuera, while micro-mobility appears to widen the scope of the 15-min liveable zone, the dispersed configuration of essential services and the suburban character of the area pose challenges that micro-mobility alone may not sufficiently address. This suggests that residents, especially those in

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outlying regions, may still face difficulties in reaching essential services within the 15-min benchmark. In contrast, Onehunga’s limited road infrastructure along the bay area restricts the effective radius of micro-mobility options. This indicates that infrastructural enhance- ments, such as the addition of a bicycle-friendly bridge, could be a critical factor in increasing accessibility within the designated liveable area.

5.4. Limitations and prospects

Future developments of this liveability mapping study could benefit from expanding the geographical scope and incorporating more comprehensive urban structures. One possible development is the cre- ation of a more refined composite liveability score at a finer spatial scale, which can be visualised on a choropleth map for a more comprehensive and detailed understanding. As Logan et al. (2022) noted, geographical boundaries can significantly impact the 15-min city metrics.

Inter-regional communication is especially complex in peripheral areas of a given region. Understanding these dynamics at a smaller geographical scale can be beneficial. Instance, residents on the outskirts of Remuera may access services in neighbouring areas, and analysing data in isolation could yield inaccurate results. Varying weights could be assigned to the 6 essential services to cater to different population groups, acknowledging that not all services, like education or leisure, are equally important to everyone. Our study also generalised the different types of amenities within the same service category; for example, educational services range from kindergartens to high schools.

Elements of the built environment, such as pedestrian infrastructure, safety factors, and the overall attractiveness of walking routes—topics well-covered in existing literature (Moura et al., 2017)—could be considered to refine the 15-min liveable area mapping. While this study maps current liveability, it has not delved into specific strategies for improvement. However, this research provides a promising framework for enhancing urban liveability, showcasing the potential for meaningful improvements in future studies.

CRediT authorship contribution statement

Jing Jiang: Conceptualization, Methodology, Writing – original draft, Writing – review & editing, Validation. Weijie Qiao: Conceptu- alization, Data curation, Software, Visualization, Writing – original draft. I-Ting Chuang: Conceptualization, Methodology, Project administration, Supervision, Validation, Writing – review & editing.

Yan Li: Software, Visualization, Investigation. Tianyi Wang: Investi- gation, Writing – original draft. Lee Beattie: Project administration, Validation.

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