Street Networks

This paper uses an extended analogy between urban structure and building structure to explore relationships between urban structure and street type, street design, street design professions and street function, leading to suggestions for
rethinking the ways design professions recognise street type and function in the design of urban structure.

This chapter presents the process of building a multimodal urban net- work model using Volunteered Geographic Information (VGI) and in particular OpenStreetMap (OSM). The spatial data model design adopts a level of simplifi- cation that is adequate to OSM data availability and quality, and suitable to the measurement of the sustainable accessibility of urban neighborhoods and city- regions. The urban network model connects a private transport system (i.e. pedes- trian, bicycle, car), a public transport system (i.e. rail, metro, tram and bus) and a land use system (i.e. building land use units). Various algorithmic procedures have been developed to produce the network model, supporting the reproducibility of the process and addressing the challenges of using OSM data for this purpose. While OSM demonstrates great potential for urban analysis, thanks to the detail of its attributes and its open and universal coverage, there is still some way to go to provide the data quality and consistency required for detailed operational urban models.

Complex systems have been widely studied by social and natural scientists in terms of their dynamics and their structure. Scholars of cities and urban planning have incorporated complexity theories from qualitative and quantitative perspectives. From a structural standpoint, the urban form may be characterized by the morphological complexity of its circulation networks – particularly their density, resilience, centrality, and connectedness. This dissertation unpacks theories of nonlinearity and complex systems, then develops a framework for assessing the complexity of urban form and street networks. It introduces a new tool, OSMnx, to collect street network and other urban form data for anywhere in the world, then analyze and visualize them. Finally, it presents a large empirical study of 27,000 street networks, examining their metric and topological complexity relevant to urban design, transportation research, and the human experience of the built environment.

Urban scholars have studied street networks in various ways, but there are data availability and consistency limitations to the current urban planning/street network analysis literature. To address these challenges, this article presents OSMnx, a new tool to make the collection of data and creation and analysis of street networks simple, consistent, automatable and sound from the perspectives of graph theory, transportation, and urban design. OSMnx contributes five significant capabilities for researchers and practitioners: first, the automated downloading of political boundaries and building footprints; second, the tailored and automated downloading and constructing of street network data from OpenStreetMap; third, the algorithmic correction of network topology; fourth, the ability to save street networks to disk as shapefiles, GraphML, or SVG files; and fifth, the ability to analyze street networks, including calculating routes, projecting and visualizing networks, and calculating metric and topological measures. These measures include those common in urban design and transportation studies, as well as advanced measures of the structure and topology of the network. Finally, this article presents a simple case study using OSMnx to construct and analyze street networks in Portland, Oregon.

The shift from Axial to Line-segment maps is one of the most important developments in Space Syntax analysis, both theoretically and methodologically. It followed a long line of investigations and discussions within the field of Space Syntax, which addressed critical issues related to the Axial map representation (e.g. Hillier and Iida,2005; Hillier,1999a,1999b; Turner,2001; Steadman,2004, Dalton, 2001). At the same time, it opened up new possibilities by allowing for the use of Road-centre-line maps in Space Syntax analysis; that is, largely available GIS-based segment maps, used in most areas of urban modelling (e.g. Turner,2007; Dalton et al.,2003). Today, several models implement syntactical analysis to Road-centre-line maps, while claiming to form valid alternatives to the Axial map, not least in capturing the perceptual and cognitive affordances presented by the environment. This paper focuses on such alternative models with a twofold aim: first, to help make well-grounded cho...

OSMnx is a Python package for downloading OpenStreetMap street network data and then constructing it into NetworkX graphs. OSMnx can simplify and correct the network’s topology automatically to ensure that nodes actually exclusively represent intersections and dead-ends. Once the network is constructed and corrected, OSMnx can calculate shortest paths from one node to another. It can also calculate various network measures relevant to urban design and transportation as well as statistical physics, including intersection density, average intersection degree, edge density, average street segment length, circuity, clustering coefficients, betweenness centrality, closeness centrality, PageRank, and many more. Its built-in visualization capabilities leverage matplotlib to easily plot routes, one-way streets, dead-ends, high/low connectivity intersections, and figure-ground diagrams of street networks and urban form.

The association between spatial patterns of retail activity and the spatial configuration of street networks was examined by means of the space syntax methodology in eight Israeli cities that represent two city types, characterized by different planning approaches and urban growth: (i) new towns, which were established according to a comprehensive city plan and modern planning concepts of “tree-like” hierarchical
street networks and “neighborhood units”; (ii) older cities, where street networks and the spatial patterns of retail activity were formed incrementally during their growth.
Unlike in older cities, retail activity in new towns concentrates in relatively less accessible and intermediate locations. This is indicated by a weak correlation between retail activity and the street network’s Integration and Choice centrality measures. The
comparison between Israeli cities illustrates the influence of urban growth and planning approaches on the formation of retail activity and its interaction with the structure of the street network.

The goal of this paper is to analyze the role and significance of the ambitus, a narrow open space between properties, in the framework of the urban history of Rome from the Archaic period to Late Antiquity. The author tackles several issues relating to this architectural feature – including its origin, function, size and the alleged gradual disappearance during the mid-Republican period –, taking into account not only the rich written documentation (literary, juridical and epigraphic), but also the archaeological evidence brought to the light by recent excavations.

Il contributo affronta il tema della viabilità urbana di Roma in età medio repubblicana da una duplice prospettiva. Da un lato, evidenzia come l’approccio combinato delle fonti disponibili consenta di ricostruire indirettamente le percorrenze della città antica, anche in contesti per i quali non siano disponibili dati archeologici. Dall’altro lato, affronta la questione della strada come realtà fisica a partire da una selezione di contesti di scavo significativi e cronologicamente ben definiti. L’obiettivo è definire le caratteristiche costruttive delle strade urbane con specifico riferimento all’arco cronologico in esame e valutare se e in che modo l’utilizzo differenziato di tecniche e materiali impiegati possa riflettere le diverse funzioni e gerarchie degli assi viari cittadini.


This contribution addresses the theme of the urban road system in Rome in the middle Republican period from a twofold perspective. On the one hand, it highlights how the combined approach of the available sources makes it possible indirectly to reconstruct the routes of the ancient city, even in contexts for which no archaeological data are available. On the other hand, it addresses the question of the road as a physical reality starting from a selection of significant and chronologically well-defined excavation contexts. The aim is to define the construction characteristics
of urban roads with specific reference to the chronological period under examination, and to assess whether and how the differentiated use of techniques and materials used can reflect the different functions and hierarchies of the city’s roadways.

Im vorliegenden Aufsatz wird das städtische Strassennetzwerk von Augusta Raurica mithilfe der Space Syntax Analysis untersucht. Dabei kommen deutliche Unterschiede in der Wichtigkeit der einzelnen Strassen zum Vorschein. Erwartungsgemäss bildet der Cardo Maximus die bedeutendste Verkehrsachse. Die verschiedenen Verkehrsteilnehmer mit und ohne Transportmittel werden im Süd-Nord-Verkehr quer über das Forum geleitet. Vom Kastelenplateau aus ist es trotz eines beträchtli- chen Gefälles die Kastelenstrasse, die gemäss Space Syntax Analysis die wichtigste Verbindung zwischen Ober- und Unterstadt darstellt.
Mit einer Visibility Graph Analysis (VGA) gelingt es, diejenigen Strassenabschnitte zu identifizieren, die über eine hohe visuelle Inte- gration verfügen. Beim Abgleich mit dem archäologischen Befund können den betreffenden Stellen tatsächlich auch besondere bauliche Strukturen zugewiesen werden.
Einleitung
Viele Wege führen durch Augusta Raurica, aber nicht alle sind von gleicher Bedeutung. Dieser Satz klingt banal, trifft aber den wesentlichen Punkt des vorliegenden Beitrags. Mit einer Gesamtzahl von 199 Strassen durchzieht ein verhältnismässig dichtes Netz das römische Stadtgebiet. Rein flächenmässig nehmen die Strassen einen nicht unwesentlichen Teil des Stadtareals ein. So sind es im Bereich der Insulae in der Oberstadt rund 18% der überbauten Fläche. Betrachtet man den gesamten Stadtperimeter, bedecken die Strassen immerhin über 10% der Gesamtfläche.
Zusätzlich zum orthogonalen Strassenraster, das die Grundlage bildet, gibt es eine Vielzahl von topografisch und städtebaulich bedingten, von diesem Raster abweichenden Verbindungswegen. In Bezug auf jedes einzelne, kleinräumige Stadtquartier sind diese Zugänge buchstäblich die Lebensadern, die eine Nutzung erst ermöglichen. Vergrössert man den Betrachtungsradius auf das gesamte Stadtgebiet, so verschiebt sich die Bedeutung der einzelnen Strassen. So leuchtet es ein, dass für die übergeordnete Erschliessung der Stadt periphere Quartierstrassen weniger wichtig sind als die Verkehrsachsen, die ganze Stadtteile, wie z. B. die Ober- stadt und die Unterstadt, miteinander verbinden.
Im Folgenden wird der Frage nachgegangen, ob wir diese subjektive Klassifizierung der Strassen auch wissenschaftlich nachvollziehbar belegen können. Die ursprünglich in
Generell widerspiegeln sich die Analyseresultate sehr gut in der Lage und Erschliessung der städtischen Architektur. Dies kann bei einer Reihe von öffentlichen und privaten Bauten nachvollzogen werden. Darüber hinaus ermöglicht die Space Syntax Analysis aussagekräftige Si-mulationen, die zum besseren Verständnis der urbanistischen Anlage beitragen.

The Roman colonial town of Augusta Raurica (Switzerland) has an extensive street network based on an orthogonal grid. However this network is not yet fully excavated. Therefore many reconstructions and additions originate from archaeological assumptions. To evaluate the town’s transport connections more objectively we have used space syntax analysis to visualize scenarios with the aim of questioning the archaeological theses with a critical eye. In order to do this, the study concentrates on the street network during the town’s heyday around 200 AD. Besides the mentioned plausibility check of consisting road course reconstructions, space syntax allows exciting observations relative to the urbanism of the town complex. The presented paper provides an insight into the current research project that uses space syntax analysis for the first time in the research field of Augusta Raurica.

The shift from Axial to Line-segment maps is one of the most important developments in Space Syntax analysis, both theoretically and methodologically. It followed a long line of investigations and discussions within the field of Space Syntax, which addressed critical issues related to the Axial map representation (e.g. Hillier and Iida,2005; Hillier,1999a,1999b; Turner,2001; Steadman,2004, Dalton, 2001). At the same time, it opened up new possibilities by allowing for the use of Road-centre-line maps in Space Syntax analysis; that is, largely available GIS-based segment maps, used in most areas of urban modelling (e.g. Turner,2007; Dalton et al.,2003). Today, several models implement syntactical analysis to Road-centre-line maps, while claiming to form valid alternatives to the Axial map, not least in capturing the perceptual and cognitive affordances presented by the environment.
This paper focuses on such alternative models with a twofold aim: first, to help make well-grounded choices in applying syntactical analysis to Road-centre-line maps; and second, to explore the methodological potentials of Line-segment maps, which are created by their flexibility, by being the least aggregated representations of street networks. The paper introduces an experimental software application to push the investigations and exploit these methodological possibilities even further.
The models discussed in this paper are: 1) Angular Segment Analysis (e.g. Turner,2007; Hillier and Iida,2005); 2) Natural Streets maps (Jiang and Liu,2007) and Continuity maps (Figueiredo and Amorim,2005); 3) Directional Distance model (Peponis et al.,2008). Based on a systematic comparison of: a) their geometric representation of the street network (the ‘map’), b) the dual-graph they calculate, and c) the measure of distance they use, we argue that they can all be seen as parametrically defined representations, based on a Line-segment map. In other words, with the same Line-segment map one could produce all of them, if a different set of angular parameters was used, to either define the graph elements (nodes, edges), or to calculate distance. These models, parametrically redefine the relation between the ‘map’ and the ‘graph’; thus, challenging the one-to-one relation between the two, that the Axial map was founded upon.
The methodological importance of this development goes beyond the specific models described in this paper. If the same Line-segment map can produce different graphs by using a different set of angular parameters, then, for instance, one could easily change the parameters to follow the latest theoretical insights on human cognition, without having to change the map. Going even further, one could develop and test different representational models to explore new theoretical and methodological paths, by using one single map. The experimental tool also presented in this paper is a step in that direction, allowing to test different models using a single software.

This paper investigates how city’s street network is related to the residential dynamics of the Arab
minority’s residential pattern in five Israeli Arab-Jewish mixed cities. Based on the the space syntax
methodological framework we analysed the metric and topological access between individual
streets. The results obtained show an association between residential pattern changes and the
relative access of individual streets to the core area of the Arab’s community (at the local and the
global level) and discontinuity of street networks. The results clearly indicate that topological
accessibility (i.e. topological distance between axial lines) is more significant in determining the
dynamics of minority-majority residential pattern than is metric distance. The findings thus
support the notion that a city’s spatial configuration provides essential conditions for urban ethnic
dynamics and the evolution of minority groups’ residential patterns. Hence, this factor might be
essential for policy making regarding minority-majority residential segregation.

The paper addresses the current need for expanding ways to understand and research aspects of urban sustainability, which are related to the social environment. Sustainability of living historic cities is related to, among other factors, their socio-spatial structure and relationships. For past urban contexts, these mostly intangible characteristics can be studied by analyses of the material aspects of urban space, which have been shaped over the long term. Shifting our focus from the preserved buildings and collections of finds onto space and spatial configurations in their own right may bring new revelations about the dynamics of the urban layouts, street networks and sensory environment. Urban streets and open spaces, specifically, may be analysed as a record of past preferences for movement patterns that are part of the sensory environment in each settlement. In this paper, urban kinesthetics are viewed as a component of social traditions and cultural heritage, and it is analysed how materially constituted networks and characteristics of the sensory environment may have contributed to the long-term social sustainability of urban settlements. As case studies, the East African towns of Mombasa, Kenya and Mozambique Island, Mozambique, represent living historical towns and sites of cultural heritage, and symbolise urban growth on a historical background reaching to the precolonial era. It is shown how the built environment of these towns have affected capacity for movement in the urban space and how movement was channelled in the urban environment. It is argued that while it is more common to understand urban architectural heritage as a collection of preserved buildings with a certain set of characteristics, adding a spatial dimension to archaeological interpretations of the built environment can aid producing relevant considerations for shaping the future of cities.

Cities consist of 20-30% streets, a gigantic infrastructure that must be maintained and developed. As such, they have the potential to contribute to tackling contemporary challenges as the increasing urbanization and climate change which place higher demands on urban environments, from quality of life, health and safety to environmental sustainability. Multifunctional streets are introduced as an answer to these challenges, as they can fulfil this multitude of functions. This paper presents a state-of-the-art, quantitative systematic review of scientific literature on the theme of multifunctional streets. Scientific papers were filtered from Web of Science and Scopus. Only scientific papers of the last 10 years were included. We will first present a survey of the field and then focus on the empirical papers that help us identify the physical factors which have been proven to support and improve the different functions of streets, from the social and ecologic to the economic and technical. The empirical studies represent 24% of the scientific papers selected, where the social function is the one most frequently studied, followed by the ecologic and the economic function. Within the social function the empirical papers in relation to health (39%) and safety (21%) dominate, followed by the ones studying liveability (9%). We will focus on empirical studies on the themes of Liveability and Safety, two important variables of the Social function, interrelating yet often conflicting.

Cities and towns have often developed infrastructure that enabled a variety of socioeconomic interactions. Street networks within these urban settings provide key access to resources, neighborhoods, and cultural facilities. Studies on settlement scaling have also demonstrated that a variety of urban infrastructure and resources indicate clear population scaling relationships in both modern and ancient settings. This article presents an approach that investigates past street network centrality and its relationship to population scaling in urban contexts. Centrality results are compared statistically among different urban settings, which are categorized as orthogonal (i.e., planned) or self-organizing (i.e., organic) urban settings, with places having both characteristics classified as hybrid. Results demonstrate that street nodes have a power law relationship to urban area, where the number of nodes increases and node density decreases in a sub-linear manner for larger sites. Most median centrality values decrease in a negative sub-linear manner as sites are larger, with organic and hybrid urban sites' centrality being generally less and diminishing more rapidly than orthogonal settings. Diminishing centrality shows comparability to modern urban systems, where larger urban districts may restrict overall interaction due to increasing transport costs over wider areas. Centrality results indicate that scaling results have multiples of approximately ⅙ or ⅓ that are comparable to other urban and road infrastructure, suggesting a potential relationship between different infrastructure features and population in urban centers. The results have implications for archaeological settlements where urban street plans are incomplete or undetermined, as it allows forecasts to be made on past urban sites' street network centrality. Additionally, a tool to enable analysis of street networks and centrality is provided as part of the contribution.

This inquiry examines four culturally diverse neighbourhoods in Istanbul with entangled street networks as places of social interaction inside and in-between different cultural groups. We analysed the streets in these neighbourhoods to provide understandings on how some networks and streetscapes are still harmoniously creating place attachment for people from different cultures. First we exam the results from the axial integration (R3) and normalised angular integration analyses (NAIN) to determine their potential to create a lively and harmonious environment. Then, each street cluster is examined using isovist path analysis, to understand the multicultural urban space experience that the street offers to its users. The findings of this study show that highly integrated street clusters have a higher chance to be perceived as a culturally diverse environment. A highly integrated main street used by several cultural groups provides a harmonious space for everyone. Kuzguncuk's long main street connecting multiple street clusters of different groups provides a diversity of cultural gathering spaces, such as schools, churches and synagogues. If the street cluster is a cultural gathering area for a single cultural group and the group preserves its common values, then it provides providing a more introvert and less culturally diverse social environment. Samatya provides an extremely highly integrated local main axis only used by Armenians and some Turkish in-migrants.

Cities and towns have often developed infrastructure that enabled a variety of socio-economic interactions. Street networks within these urban settings provide key access to resources, neighborhoods, and cultural facilities. Studies on settlement scaling have also demonstrated that a variety of urban infrastructure and resources indicate clear population scaling relationships in both modern and ancient settings. This article presents an approach that investigates past street network centrality and its relationship to population scaling in urban contexts. Centrality results are compared statistically among different urban settings, which are categorized as orthogonal (i.e., planned) or self-organizing (i.e., organic) urban settings, with places having both characteristics classified as hybrid. Results demonstrate that street nodes have a power law relationship to urban area, where the number of nodes increases and node density decreases in a sub-linear manner for larger sites. Most m...

The street network of the Roman town of Augusta Raurica – reviewed with the help of space syntax

The Roman colonial town of Augusta Raurica (Switzerland) has an extensive street network based on an orthogonal grid. However this network is not yet fully excavated. Therefore many reconstructions and additions originate from archaeological assumptions. To evaluate the town’s transport connections more objectively we have used space syntax analysis to visualize scenarios with the aim of questioning the archaeological theses with a critical eye. In order to do this, the study concentrates on the street network during the town’s heyday around 200 AD. Besides the mentioned plausibility check of consisting road course reconstructions, space syntax allows exciting observations relative to the urbanism of the town complex. The presented paper provides an insight into the current research project that uses space syntax analysis for the first time in the research field of Augusta Raurica.