Elements of Access … On Sale Now

Now available: Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen. 342 pages, 164 Images (most in color). Published by the Network Design Lab. About the Book Nothing in cities makes sense except in the light of accessibility.  Transport cannot be understood without reference to the […]

Elements of Access

Now available: Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen. 336 pages, 164 color images. Published by the Network Design Lab. About the Book Nothing in cities makes sense except in the light of accessibility.  Transport cannot be understood without reference to the location of […]

Elements of Access: Hierarchy

In binary networks, the focus is on whether or not a connection between two nodes exists.  However, not all links (or nodes) are created equal, particularly when it comes to transportation networks.  When we know about the presence of a link as well as the strength of that link, it is called a valued network.  […]

Elements of Access: Meshedness

Urban planners and engineers have long been interested in measuring street connectivity and typically do so with relatively simple measures such as the link to node ratio (called the Beta Index in the Transport Geography field), which divides the total number of links (i.e. road segments between intersections) by the total number of nodes (i.e. […]

Elements of Access: Clustering

When we have nodes or links with high Betweenness values, it is often because our network is split into various sub-groups that can be called clusters.  Clusters tend to have their own unique set of properties, so it is useful to be able to identify clusters quantitatively. While there are a growing number of clustering […]

Elements of Access: Betweenness

Degree is often good for measuring local circumstance, but adequately characterizing centrality is a bit more complicated.  When trying to figure out centrality in terms of how connected and influential a node or link is, it is useful to get a sense of relative network flow through a particular node or link. Betweenness measures attempt […]

Elements of Access: Degree

Centrality measures help gauge the overall importance of a node.  In other words, how connected and how influential is a node within the overall network? One of the simplest measures of centrality is Degree, which measures the number of connections between a node and all other nodes.  For instance if we are considering a street […]

Elements of Access: Introduction to Topology

Networks play a role in nearly all facets of our daily lives, particularly when it comes to transportation. Even within the transportation realm lays a relatively broad range of different network types such as air networks, freight networks, bus networks, and train networks (not to mention the accompanying power and communications networks). We also have […]

Elements of Access: Unitary vs. Modular Architectures

Designs might be comprised of individual, discrete building blocks (modules) that are combined into a pattern, or may be holistic (unitary) so that a small part cannot simply be interchanged with something similar without breaking the whole design. Most things are combinations of the two. Software has moved very much to modular architecture, and as […]

Elements of Access: Roundabouts

Most people I talk with about roundabouts probably fall somewhere on the love-hate spectrum between extreme dislike and hate.  One reason for such an unenthusiastic assessment – especially for Americans – can likely be traced to some common misconceptions about what we are actually talking about when we talk about roundabouts. Having grown up near […]