Walk scores help people find walkable communities in which to live, as well as help them determine how walkable their current neighborhood is. The Walk Score Web site uses Google Maps, specifically Google's Local Search API (application programming interface), to find the stores, restaurants, bars, parks and other amenities within walking distance of any address you enter. Walk Score currently includes addresses in the United States, Canada and the United Kingdom.
Using a patent-pending algorithm, Walk Score establishes neighborhood boundaries using data from the real estate information Web site Zillow, calculates the distances from your entered location to amenities in your walkshed via Google Maps, and weighs in the population density information from the 2000 census.
Based on these three fold criteria, Walk Score ranks an address with a score between zero and 100 (100 being the best). Amenities within 0.25 miles (0.4 kilometers) of the central location are given the most points -- the greater the distance, the fewer points are awarded. Places farther than one mile (1.6 kilometers) away are given zero points. Scores are broken into five categories. The most desirable scores are between 70 and 100: 90-100 is considered a walkers' paradise where residents don't need to own a car; 70-89 is very walkable and residents probably don't need a car. Below 70 and you get into the neighborhoods that are somewhat walkable but probably necessitate public transportation, a bike or a car for getting around. A score below 50 means the community is car-dependent, and a score below 25 means residents need to drive everywhere.
A few caveats about scoring: Walk Score depends on the available data sources. If it doesn't know about the Starbucks located just across the street from your house, it can't include it in its rankings. Luckily, you have the opportunity to add missing community amenities to Google's Local Search API and in doing so, increase your walk score rank. Walk Score is also blind to some important details -- it doesn't include such factors as topography, street design, available public transportation or bodies of water in its rankings. It calculates as the crow flies, which means that if there's a lake between you and the closest coffee shop, Walk Score assumes you're more than happy to swim for your caffeine fix.
The Walk Score algorithm also doesn't rate a neighborhood on how pretty it is, but rather how easy it is to live car-free. If you live near a nature preserve or hiking trails, that greenery may improve your quality of life, but it won't improve your walk score.