MultiCAST - Street Network Analysis

Street Network Analysis

GENERAL INFORMATION

Network Analysis encompasses the examination and assessment of both the structural and functional attributes of urban networks, encompassing both vehicular street systems and pedestrian pathways. This field stands as a cornerstone in the realms of urban planning, transportation engineering, and geography, offering invaluable insights into the connectivity, accessibility, and efficiency of road systems and pedestrian infrastructures within a city or region.

The relevance of Street Network Analysis extends far beyond theoretical exploration; it is a pivotal tool that guides the design and optimization of transportation systems, informs land use planning, and contributes to the overall livability of urban areas. By evaluating both vehicular and pedestrian networks, this approach recognizes the diverse modes of urban mobility, catering to the needs of pedestrians alongside traditional vehicular traffic.

Street networks often exhibit varied characteristics in urban landscapes, including grid patterns, hierarchical structures, or irregular configurations. Quantifiable metrics such as connectivity, density, centrality, and accessibility become instrumental in deciphering these features. This comprehensive understanding is critical for identifying potential bottlenecks in both vehicular and pedestrian traffic, optimizing transportation routes, and enhancing the overall functionality and accessibility of urban spaces.

The focus on pedestrian networks underscores the importance of accommodating diverse modes of movement within cities. Pedestrian pathways, alongside vehicular streets, contribute significantly to the urban fabric, shaping the pedestrian experience and influencing the accessibility of key locations. Urban Network Analysis, therefore, plays a pivotal role in ensuring that the design and planning of pedestrian infrastructures align with the broader goals of creating safe, accessible, equitable, and vibrant urban environments.

Street Network Analysis vs. Space Syntax

Street Network Analysis. Primarily involves the quantitative assessment of the connectivity, accessibility, and efficiency of street or pedestrian networks. It utilizes metrics and analytical tools to understand the structural characteristics of road systems and pedestrian infrastructures, with applications in urban planning, transportation engineering, and emergency response planning. The emphasis is on the network’s physical layout, traffic flow, and connectivity.
Space Syntax. Theoretical and analytical framework that explores the relationship between spatial configurations and human behavior. Developed by architects and urban planners, Space Syntax examines the social and functional implications of spatial layouts, considering factors such as visibility, connectivity, and accessibility. It goes beyond the physical structure of streets to investigate how spatial arrangements influence social interactions and user experiences.

TYPES OF ANALYSIS

Street Network Analysis is fundamental in urban planning, transportation engineering, and geography. Analyzing the structural and functional characteristics of both vehicular and pedestrian networks offers invaluable insights into the connectivity, accessibility, and efficiency of urban infrastructures. This is achieved by means of different types of analysis and metrics.

Connectivity Analysis

Connectivity analysis focuses on understanding how well different parts of a street network are interconnected. Connectivity analysis examines how well different parts of the network are connected to each other. It can help identify areas of the network that are well-served by the transportation system, as well as areas that are isolated or difficult to reach.

Accessibility

Accessibility analysis evaluates the ease with which different locations can be reached within a street network. Factors such as travel time, distance, and available routes are considered to optimize urban layouts, enhancing overall accessibility for residents, businesses, and public services. These types of analysis collectively form a comprehensive toolkit for understanding and optimizing urban networks. By incorporating metrics such as reach, gravity, betweenness, straightness, and service area, planners and researchers gain multifaceted insights into street network structural and functional characteristics, contributing to the development of more efficient, accessible, and livable urban environments.

Service Area. Service Area analysis, or Isochrone analysis, delineates the geographical area reachable within a specified travel time or distance. In other words, the Service Area metric is used to determine the area that can be reached within a certain distance or travel time from a specific point on the network. This is particularly useful in accessibility studies, for instance, to identify areas within a 15-minute walk of a transit station.

Reach. Reach analysis measures the potential accessibility of specific locations within an urban network. It is a measure of the extent of an area that can be accessed from a particular point, considering the connectivity and layout of the network. It can be used to evaluate the effectiveness of a transportation network in providing access to different parts of a city. This metric aids in identifying central areas with high accessibility, guiding decisions for urban development and infrastructure improvements.

Gravity. Gravity analysis is a widely employed method in transportation planning that assesses the strength of interaction between different locations within a street network. This approach is instrumental for estimating the flow of people, goods, or information between various points in a network. The fundamental principle guiding gravity analysis is that the interaction intensity between two places is directly proportional to the product of their sizes or populations and inversely proportional to the distance that separates them. The modeling of distance in gravity analysis often utilizes a decay model, which can take on linear or exponential forms. This modeling technique allows for a nuanced understanding of how the interaction strength diminishes as the distance between locations increases.

Centrality Analysis

Centrality analysis evaluates the importance of specific nodes or segments within a street network. Metrics such as degree centrality or closeness centrality are employed to identify key locations that play crucial roles in facilitating efficient transportation and connectivity. In other words, centrality analysis is used to identify the most important nodes (intersections) or edges (streets) in a network. It helps in understanding the influence of a particular node or edge’s influence on the network’s flow.

Degree Centrality. Degree centrality measures the number of connections a node has within the network. It is a simple measure that counts the number of edges connected to a node. Nodes with a high degree centrality value are pivotal in terms of connectivity, indicating central hubs within the urban network.

Closeness Centrality. Closeness centrality assesses how quickly a node can reach all other nodes in the network. It simply measures how close a node is to all other nodes in the network. Nodes with high closeness centrality are strategically positioned for efficient access to other locations, enhancing overall network connectivity.

Flows Modelling

Flow modeling, a critical aspect of street network analysis, focuses on the movement or flow within a network. It encompasses both vehicular traffic and foot traffic, also known as pedestrian flow. This comprehensive approach helps understand and predict movement patterns, which can be particularly useful for urban planning and transportation policy. The analysis of vehicular traffic aids in understanding the dynamics of traffic patterns, congestion points, and the overall efficiency of the transportation network. On the other hand, the study of pedestrian flow provides insights into walkability, accessibility of facilities, and the design of pedestrian-friendly spaces.

Betweenness. This is a centrality measure used in network analysis. The betweenness centrality of a node in a network is defined as the fraction of shortest paths between pairs of Origins and Destinations that pass by a particular location. If more than one shortest path is found between two nodes, as is frequently the case in a rectangular grid of streets, then each of the equidistant paths is given equal weight such that the weights sum to unity. In the context of flow modeling, betweenness can be used to model pedestrian flows between origins and destinations in built environments.

Patronage. This metric estimates the use of spatial facilities over networks. It can summarize how many origin points or origin point weights are closest to each facility in a given set of facilities. This can be particularly useful in urban planning for estimating the potential usage of different facilities, such as shops, parks, or transit stations, based on their location in the street network.

Patronage/Betweenness. The combination of the two (as implemented in the UNA toolbox) can be used to model pedestrian or bicycle flows over spatial networks. The tool calculates and visualizes how many trips are likely to pass different network edges or Observer points, given a set of trips between Origins and Destinations in a network. It can be used to approximate foot or bike traffic at particular locations or across an entire network.

Network Structure

Network structure is a key aspect of street network analysis that focuses on a street network’s structural and morphological properties. It provides insights into the layout and connectivity of the network, which are considered to be the key factors that shape dynamic urban traffic flow.

Straightness. Straightness, also known as directness, is a measure of how closely the actual travel path between two points follows the straight-line distance. In urban networks, a high degree of straightness often indicates efficient connectivity. However, it may also reflect a grid-like street pattern, which may only sometimes be the most desirable urban form due to other considerations such as land use diversity and walkability.

MAIN SOURCES OF DATA

A multi-faceted approach encompassing GIS technology, traffic flow data, GPS tracking, on-site counting, and demographic information forms a robust foundation for informed urban planning decisions.

Geographic Information Systems (GIS). GIS technology seamlessly integrates spatial data, facilitating the creation of detailed maps and in-depth analysis of street network characteristics. Serving as a versatile platform, GIS enables the storage, analysis, and visualization of data related to road networks, land use, and other pertinent factors crucial for comprehensive urban planning.

Traffic Flow Data. Real-time and historical traffic flow data, sourced from an array of sensors, cameras, and monitoring devices, provide invaluable insights into the dynamic behavior of street networks. This information is essential for understanding congestion patterns, pinpointing high-traffic areas, and strategically planning future infrastructure development.

GPS Tracking. GPS tracking enhances the precision of street network analysis by capturing real-time location data from various sources, such as vehicles and mobile devices. This technology contributes to a more accurate understanding of movement patterns, aiding in the optimization of transportation routes and the identification of key nodes in the network.

On-Site Counting. On-site counting involves the deployment of physical counters and sensors at specific locations to observe and quantify pedestrian and vehicular movements directly. This hands-on approach provides granular data, offering additional layers of detail for a comprehensive analysis of street network dynamics.
Urban Surveys and Census Data. Data derived from urban surveys and census records supply essential demographic information that complements street network analysis. Understanding population distribution and movement patterns is crucial for predicting transportation demands and optimizing road networks to align with the evolving needs of urban environments.

RELEVANT APPLICATIONS

Urban Planning and Design: Street Network Analysis is a cornerstone in guiding urban planners toward designing cities with efficient and accessible transportation systems. This application intricately considers factors such as pedestrian pathways, cycling lanes, and public spaces by emphasizing walk-accessibility, active mobility, and non-motorized modes. In prioritizing these elements, planners contribute significantly to creating sustainable and livable urban environments. This holistic approach not only encourages physical activity and reduces environmental impact but also enhances the overall quality of life for residents. The focus on accessibility and equity ensures that the benefits of well-designed street networks are distributed equitably across diverse communities.

Transportation Engineering: In the realm of transportation engineering, Street Network Analysis has become a vital tool for optimizing traffic flow, reducing congestion, and enhancing safety. This application extends its focus beyond vehicular traffic to consider active mobility modes such as walking and cycling actively. By identifying critical nodes and links, engineers can design road networks that not only facilitate the efficient movement of people and goods but also prioritize the safety and accessibility of pedestrians and cyclists. This holistic approach ensures a well-balanced transportation infrastructure that caters to diverse modes of mobility, fostering inclusivity and equity in urban transportation planning.

Emergency Response Planning: Street Network Analysis plays a pivotal role in emergency response planning, ensuring a swift and coordinated response during crises. By identifying the most effective routes for evacuation, emergency services, and resource distribution, this application takes into consideration walk-accessibility and non-motorized infrastructure. The incorporation of pedestrian pathways into emergency plans is essential for addressing the needs of vulnerable populations and ensuring that evacuation routes are inclusive and accessible to everyone. In times of crisis, Street Network Analysis becomes crucial in building resilient and responsive urban environments, promoting equity in emergency preparedness and response.

Logistic and Freight Planning: Street Network Analysis extends its reach into the realm of logistics and freight planning, playing a pivotal role in optimizing the movement of goods within urban environments. This application is particularly crucial for ensuring efficient supply chain operations and minimizing the environmental impact of freight transportation. By incorporating an emphasis on accessibility and equity, logistic and freight planning can contribute to designing distribution routes that consider the needs of diverse communities. The application of Street Network Analysis in logistics aligns with the broader goal of creating sustainable and equitable urban environments where the benefits of efficient freight transportation are shared inclusively among residents.

RELATED LINKS AND ADDITIONAL RESOURCES

- ESRI: ESRI is a global leader in GIS (Geographic Information System) technology. Their platform provides tools for mapping, spatial analysis, and street network analysis.
- UNAtoolbox: The UNAtoolbox is a comprehensive set of tools for urban network analysis. Developed for ArcGIS and Rhino, it offers a range of functionalities for the analysis and visualization of street network analysis.
- World Bank – Urban Transport: The World Bank’s portal on urban transport provides resources and reports on sustainable urban mobility and transportation planning.
- TRB: TRB, part of the National Academies of Sciences, Engineering, and Medicine, provides research and resources related to transportation, including street network analysis.
- APBP: APBP is a professional association that focuses on promoting walkability and bicycle-friendly communities. Their resources include guidelines and best practices for active transportation planning.
- NACTO: NACTO provides design guidelines for streets and transportation in urban areas, with a focus on sustainable and equitable mobility solutions.
- APA – Transportation Planning Division: The APA’s Transportation Planning Division offers resources, publications, and events related to transportation planning, including street network analysis.
- OpenStreetMap: OSM is a collaborative mapping platform that provides open and freely accessible geographic data. It can be a valuable resource for obtaining base maps and street network data.

*Images from

https://cityform.mit.edu/en