Intersection density captures the neighborhood connectivity and directness with which a traveler in a network, especially a pedestrians or bicyclist, is able to traverse. It is measured as the gross density of street intersections in a given area. Intersection density is derived from counting the number of junction points or nodes at intersections and dividing by the gross land area in square miles. This measure of street intersection density excludes auto-oriented road intersections. Areas with high connectivity have an integrated grid network road pattern allowing people to connect to a large range of destinations in all directions within a short walking distance. Intersection density is typically highest in urban areas, especially a Downtown core or older town centers of cities exhbiting a gridded street network. In contrast, a more disconnected road pattern is associated with rural and suburban areas with large blocks and cul-de-sac road configurations containing a lower neighborhood intersection density. Intersection density forms one of the core four components of the walkability index.1
Figure 1: Urban, gridded street network -- high intersection density
Figure 2: Suburban, cul-de-sac -- lower intersection density
An example of a highly connected road network and a more disconnected road network.
Intersection density is derived from the junction points or nodes connecting road segments. Intersections counts are determined by calculating the number of network junctions having 3 or more road segments intersecting the junction. The weighted intersection density measure is a weighted sum component of four intersection density metrics. The measure does not include auto-oriented intersections for roads where pedestrians are not permitted including limited access roads and entrance/exit ramps. Both three and four leg intersections for both multi-modal intersections (where pedestrians and vehicle are permitted) and pedestrian-oriented intersections were utilized with three-way intersections with a reduced relative weight due to a lack of promoted connectivity. The intersection counts by Census block group is the numerator and the gross area denominator for intersection density is the total land area in square miles to yield the intersection density ratio.Formula:
The MSA level value is the unweighted mean of the values of all block groups in the MSA.
- Weighted intersection density = ((count of three-way multi-modal intersections * 0.667) + (count of three-way pedestrian-oriented intersections * 0.667) + count of four-way multi-modal intersections + count of four-way pedestrian-oriented intersections) / total land area in square miles
This indicator was calculated by U.S. Environmental Protect Agency (U.S. EPA) using data from the sources listed below.
- United States Environmental Protection Agency (EPA) Smart Location Database, 2013.
- NAVTEQ NAVSTREETS U.S. Road Network, 2011 Q3.
RELATED ACADEMIC PUBLICATIONS
- Frank, L.D, Engelke, P. O., & Schmid, T. L. (2003). Health and Community Design: The Impact of the Built Environment on Physical Activity. Washington DC: Island Press.
- Ding, D., Sallis, J.F., Conway, T.L., Saelens, B.E., Frank, L.D., Cain, K.L., Slymen, D.J. (2012). Interactive Effects of Built Environment and Psychosocial Attributes on Physical Activity: A Test of Ecological Models. Annals of Behavioral Medicine. 44(3), 365-374.
- Frank, L.D., Sallis, J.F., Saelens, B.E., Leary, L., Cain, K.L., Conway, T.L., Hess, P. (2010). The Development of a Walkability Index: Application to the Neighborhood Quality of Life Study. British Journal of Sports Medicine. 44, 924-933.
Frank, L.D., Sallis, J.F., Saelens, B.E., Leary, L., Cain, K.L., Conway, T.L., & Hess, P.M. (2009). The Development of a Walkability Index: Application to the Neighborhood Quality of Life Study. British Journal of Sports Medicine. 44(13), 924-933.