Walk Score Rankings Methodology
We sampled the Walk Score of 10,017,714 locations to rank 2,500 U.S. cities and 10,017 neighborhoods on walkability for 2011.
Planners and Researchers: Learn about using Walk Score data in your research.
|Walk Score algorithm||Measures the walkability of individual addresses based on proximity to nearby amenities.|
|City boundaries||Provided by the U.S. Census 2010 Incorporated Places. Note: this is the city boundary not the entire metro area.|
|Neighborhood boundaries||Provided by Zillow.com.|
|Population data||Used to weight Walk Score by population density, data from the 2010 U.S. Census.|
The Walk Score Point Grid and Population Density Weighted Walk Score
Within a city or neighborhood, we sample the Walk Score of approximately each city block. To do this, we create a grid of points spaced roughly 500 feet apart (.0015 decimal degrees; exact distance will vary with latitude).
We weight the Walk Score of each point by population density so that the walkability rankings reflect where people live and so that neighborhoods/cities do not have lower scores because of parks, bodies of water, etc.
We use the following algorithm to calculate a population density-weighted Walk Score:
For each point in the grid:
- Expand each point by .00075 decimal degrees to create a grid cell
- Intersect the grid cell with the census blocks it intersects and for each census block:
- Calculate % of the census block the grid cell intersects
- Multiply that % by the total population of that census block
- Sum these partial populations to get the grid cell population
- Add the grid cell population to a variable called total_population
- Calculate the Walk Score at the center of the grid cell and multiply it by the grid cell population to get the weighted Walk Score
- Add the weighted Walk Score of this grid cell to a variable called weighted_walk_score
To calculate the Walk Score for an entire neighborhood/city, divide weighted_walk_score by total_population for the points within the boundary of the neighborhood/city.
The population total we display for neighborhoods/cities is the total_population variable mentioned above.
To calculate the Walk Score for a city, we include only points within the city boundary. This may exclude points that are inside a Zillow neighborhood boundary but outside the city boundary.
Walkability Heat Map and Neighborhood Rollovers
Heat maps: To generate the walkability heat map, we create a very small grid and assign each grid cell a color based on the Walk Score of the surrounding points. A spectrum of red to green is used to represent the range of Walk Score from 0 to 100.
Walk Score Data for Planning and Research
We provide walkability, public transit, and road connectivity data to researchers and planners. Learn more about using Walk Score data in your research.