Walk Score is a method for calculating a rating (from zero to 100) for a given address, based on the walking distance from that address to a variety of necessary amenities that a typical person needs on an average day. Walk Score was initially conceived to help individuals find apartments to rent in what the founders of the metric deemed walkable neighborhoods. But rather than apply the walkable label at will, they created a method to measure each address, enabling users to compare the walkability of one address to another.

This comparison of apartments (and now other residences) continues to be available on the Walk Score website. Still, the benefits of the measure have grown significantly since it was created in 2007. Through Walk Score Professional, the organization provides data and digital code in the form of widgets and badges that enable users to display Walk Scores on their websites, integrating them with real estate listings or other data sets. Today more than 30,000 websites feature Walk Score data.

Additionally, the measure is being applied to all addresses and property types in the U.S and Canada. Walk Score has expanded beyond individual address scores to rank neighborhoods and entire cities. The ever-growing body of data compiled by Walk Score is being used by researchers in various fields, such as real estate valuation, insurance actuarial analysis, and healthcare.

The Walk Score Calculation

The Walk Score algorithm has been modified over the years, and as expected, the details are proprietary. However, the overall calculation involves measuring the walking distance from a particular address to nearby amenities in seven broad categories: groceries, dining and drinking, shopping, errands, parks, schools, and culture and entertainment. Destinations within a quarter-mile walk contribute maximum points to the Score for that address, with fewer points awarded for amenities up to 1.5 miles away. The nearest business or facility in each category contributes more than the second or third closest, and so on. Categories are weighted that the categories covering groceries, dining and drinking, shopping, and errands impact score the most.

Other contributors to the Score include population density and, interestingly, intersections. The Score increases as the population density of an area rise. This measure was adopted because, for example, dense neighborhoods with numerous people can offset a large body of water that is not walkable and might dilute the Score for the area around an address. Additionally, more intersections along a route increase the Score because it means that there is a network of sidewalks and short blocks, offering many, rather than just one or two, walking routes one can take from a given address to the sought-after amenities.

The result is normalized to fit a 0 to 100 scale; 0 is the low score, meaning the area is car-dependent, and all errands require a car. The high score is 100, indicating that a car is not needed to live in the area because daily errands can be carried out on foot.

Amenities Included in the Calculation

The Walk Score measures walking distance from a location to amenities in seven categories.

Dining and Drinking

They look at the distance to dining and drinking, so [they identify] restaurants, bars, coffee shops, cafes, those sorts of things.

Groceries

Distance to groceries is also measured, what they're trying to capture with [this category are places where] you can get the ingredients for a relatively healthy meal, so [that means] fresh produce, milk, eggs, bread, those sorts of things. A convenience store where you can get a can of chili and a hot dog does not meet these criteria, so it really needs to be a place where you can shop to meet your everyday meal needs in a relatively healthy way.

Retail

This includes retailers that sell clothing, books, gifts, or establishments that generally fall into the categories of gifts, novelty, apparel, and accessories.

Errands

This includes places like banks, dry cleaners, pharmacies, and other health and service-related businesses.

Schools

Elementary through high schools are included in this category, but not necessarily colleges and universities or specialty schools that offer karate or music lessons.

Parks

Included here are green space, pocket parks, central parks, trails, and trail access areas.

Culture and Entertainment

Movie theaters, live theaters, museums, galleries, concert venues, etc., are counted.

Collecting Walk Score Data

The data infusing Walk Score is collected primarily from data sources (some of which are mentioned in this article), but feedback from users is also incorporated. The majority of the amenity data is coming from a company called Factual, which recently was purchased by Foursquare. Factual provides data on the location of restaurants, grocery stores, and various other vendors. Walk Score also works with Great Schools.org to ascertain the location of K-12 schools and uses data from the U.S. Census Bureau to gather population metrics. Openstreetmap.org provides information about road networks, walking paths, bike paths, and other mobility infrastructure.

Users contribute as well. If you go to their website and look up your house and see that they're missing a restaurant down the street, you can add that, and we'll include it when they update the Score for your house the next time. Conversely, if a user sees a convenience store listed as a grocery store, you can move it to the shopping category, which is where we put convenience stores; or if it is closed, you can remove it, and we'll take that information in as well. They also have quite a few users that contribute information, noting they tend to be active in one particular location, and they'll go in and make sure that everything within their area is as accurate as it can be.

Updates for individual addresses are made roughly every six months on a rolling basis; neighborhood, city-level, and census tract scores are assessed about once a year.

Short Blocks and Many Intersections

Pedestrian friendliness often evokes the image of a sidewalk, but just because a sidewalk exists does not mean an area is pedestrian-friendly. The Walk Score algorithm is informed not just by the existence of sidewalks but also by their accessibility. Walk Score quantifies the degree to which certain areas are pedestrian-friendly by looking at average block length and intersection density. A lot of people would assume that they look for sidewalks, but there isn't a national database of sidewalks in a usable format.

Sidewalks aren't necessarily as good a proxy for pedestrian friendliness as average block length and intersection density or the number of intersections per square mile. More intersections mean shorter blocks. If you think about a neighborhood or a city that's built on a grid system where you have blocks, and you can walk around the block one way or the other, this creates a variety of ways to move in any direction. Intersection density and the length of blocks are good proxies for the speed limit, for walking routes, for access to nearby amenities, for narrower streets, all of which are also better for pedestrians.

That sidewalk may not be accessible unless you have a lighted intersection that gives you enough time to cross. Additionally, there may be a large parking lot between the sidewalk and the street in front of the strip mall. In this example, the existence of a sidewalk is not a proxy for walkability because crossing the street to access the sidewalk and traversing the parking lot to get to the shopping center add distance to the effort.