Huge thanks to WBG member Kayla A. Kaiser who recently completed an analysis of Glendale’s bicycle plan to compare it to the national average. Our technical expert and nerd friends should really enjoy this one.
There are a variety of ways of characterizing networks in the field of transportation geography and network science. A classic set of connectivity measures includes beta, gamma, and alpha indices. We compared the current bicycle infrastructure in Glendale with the City of Glendale Bicycle Transportation Plan (page 75, Map 6-1) and 72 US cities of varying size and population in Table 1. It is clear that the current bikeway network in Glendale is behind the national average, whereas the proposed bikeways would propel Glendale to the forefront of the nation.
Links are defined as pathway segments between two nodes. Nodes are intersections or termini at the end of a bikeway segment. The beta index is a ratio of links to nodes. Higher beta values constitute a more complex network, whereas lower beta values mean that a cyclist would have to ride in traffic where the network fails to connect points of interest. The gamma index is a ratio of observed edges to the theoretical maximum. Higher values of gamma indicate greater internal connectivity and increased redundancy in the network, providing a cyclist with greater choices. The alpha index is the ratio of the number of actual circuits to the maximum number of circuits. If the value is zero, then it indicates no circuits; and if the value is 1 then it indicates a complete interconnected network.
In a recent article in the journal Transportation beta, alpha, and gamma indices were correlated with the number of bicycle commuters per 10,000 commuters. With and without correcting for city size and demographics, Schoner found that network connectivity (as quantified by alpha, beta, and gamma indices, among other factors) is positively correlated with increased numbers of bicycle commuters. The bottom line is that Glendale can do better and if we keep pushing for increased funding for bicycle projects in the San Fernando Valley Council of Governments Mobility Matrix perhaps we can increase our city’s profile among bikeable cities with interconnected networks of bike lanes.