Publication Detail

Brief: Impacts of Network Connectivity on Passenger Vehicle Use and Greenhouse Gas Emissions



Suggested Citation:
Handy, Susan L., Gil Tal, Giovanni Circella, Marlon G. Boarnet (2014) Brief: Impacts of Network Connectivity on Passenger Vehicle Use and Greenhouse Gas Emissions. Institute of Transportation Studies, University of California, Davis, Brief UCD-ITS-RR-14-47

Network connectivity describes the quality of the connections that link each of the points in a community with one another. The structure of the street network, defined in terms of the patterns of streets and intersections, determines the directness of these connections, which often differ by mode (Handy, et al. 2003). From the transportation standpoint, network connectivity is defined with respect to the directness of connections to potential destinations.

Network connectivity is shaped by local codes and standard practices. Subdivision ordinances, in particular, often set standards that encourage street networks with relatively low connectivity (Handy, et al. 2003). Professional guidelines, such as those adopted by the Institute of Transportation Engineers, have also encouraged development patterns characterized by low-connectivity networks for many decades (Southworth and Ben-Joseph 1997). As a result, the structure of residential street networks in the United States has evolved over time, as illustrated in Figure 1, from “grids,” which were common prior to World War II, to networks dominated by cul-de-sacs. Over the last decade, however, many communities throughout the United States have revised their standards to encourage a return to grid networks (Handy, et al. 2003).

Because of the strong association between the era of development and the layout of the street network, connectivity is likely to be correlated with other characteristics of the built environment. For example, pre-World War II neighborhoods tend to have grid networks, small neighborhood stores, and narrower streets, and are located closer to the center of the city, while subdivisions developed during the 1980s are characterized by cul-de-sacs, strip malls and “big box” stores, and wider streets, and are located farther from the center. Therefore, the year in which a neighborhood was first developed often serves as a good proxy for connectivity (with older neighborhoods having greater connectivity), and connectivity, in turn, often serves as a useful proxy for a broader set of characteristics typical of that era. Separating the effect of connectivity on vehicle miles traveled (VMT) and greenhouse gas emissions from the effects of these other characteristics can be difficult.

Key words: Network connectivity, city planning, streets