Proposal Title: Measuring Connectivity for Bicycling and Walking
Principal Investigator: Jennifer Dill, Ph.D., School of Urban Studies and Planning, Portland State University

Advocates of New Urbanist and neo-traditional planning concepts include street connectivity as a key component for good neighborhood design. Street networks that are more grid-like are preferred over networks that include many cul-de-sacs and long blocks, thus increasing distances between destinations. The increased distances are thought to discourage walking and bicycling and, thus, physical activity. While intuitively attractive, there is limited empirical research at this time making this connection. There is also debate over how to measure connectivity and what levels of connectivity are appropriate. The current debate is particularly unclear because street connectivity is proposed to meet multiple, sometime conflicting objectives. In addition, most efforts to date have focused on the street network, which may differ from the pedestrian and bicycle network.

The objective of this project is to develop measures of network connectivity that relate to bicycle and pedestrian behavior. We intend to develop measures that can be used by researchers developing empirical evidence linking (or not) connectivity to travel behavior, and planners who want to develop standards for new and existing development. We will develop the measures using GIS tools and data from the Portland, OR region and will evaluate the feasibility of applying the measures to other areas. The effort involves three steps:

1. Develop measures of network connectivity that reflect pedestrian and bicycle access. Implement these measures using the Portland, Oregon network. Measures may include link-to-node ratio, block length, intersection density, and other measures. Consideration will be made for measuring differences between the street network and the bicycle and pedestrian network. This step will also address the issue of scale, e.g., what size of an area should the measure be applied to?

2. Compare measures of connectivity to pedestrian and bicycle performance measures, such as route distances and pedestrian route directness. The project will explore whether and how topography could be incorporated into the measures of performance. We will then evaluate the relationship between these measures. Based upon the analysis, we will make recommendations as to which measures are most appropriate for use when linking bicycle and pedestrian travel to connectivity.

3. Evaluate implementation issues, using a nationwide survey of local jurisdictions. We do not want to develop a measure that requires information unavailable in most other jurisdictions. The goal is to have a set of measures that can be used for research and planning in a wide range of jurisdictions. The cities will be contacted to determine whether the data necessary to compute the measures of connectivity is available in a GIS file format now or in the near future. From this information we will further refine our recommendations for measures to use in future research and planning.