Levittown, PA, one birthplace of the suburbs, is a 32.

Master-planned city Columbia, MD, averages 44.

The nation's capital, Washington, D.C., gets a 68.

Highly rated for sustainability practices, Portland, OR, comes in at 80.

Liberal, edgy San Francisco, CA gets a 94.

A perfect score is 100.

The points are for walkability and a new website called Walk Scorewants to get you, well, walking in the right direction.

Doing for home shoppers what other websites do to pinpoint the best schools, least crime, most attractions and other demographic desires, Walk Score helps you find homes in locations dotted with desirable destinations -- retailers, restaurants, schools, parks, and other attractions.

Measuring walkability, down to the home address level, to underscore the benefits of living in a walkable community, is an offshoot of the Seattle-based Sightline Institute (formerly Northwest Environment Watch), a not-for-profit sustainability research think-tank.

The website uses algorithms to extract walkability characteristics from Google Maps API.

A Walk Score is calculated based on the distance to walkable locations near an address. Each location gets scored, then the tally is combined into the Walk Score.

Sightline says, in general, the most walkable neighborhoods are those that tend to have:

• A discernible center, say, a shopping district, main street, or public space.

• Density rather than sprawl. Compactness brings people closer to destinations and makes cost-effective use of public transit.

• Mixed income, mixed use. Housing for all income and demographic groups working in the neighborhood. Businesses and residences in the mix.

• Parks and public gathering and playing spaces.

• Accessibility to all, people in wheelchairs, people who like benches, shade and sidewalks.

• Well-connected, speed controlled streets in a connected grid that improves traffic with ample routes to any destination. Narrow streets that control speed. Shaded by trees for protection.

• Buildings are placed close to the street to cater to foot traffic. Parking in the back.

• Schools and workplaces near enough for most to walk to.

However, the Walk Score producers concede, their system calculates walkability largely by locating nearby and commonly desired destinations, which makes the score an approximation of walkability rather than a scientific representation.

"Yes, it's definitely an imperfect tool. We don't select the destinations, they are part of the data from Google maps, so it gives the Walk Score based on what it's (Google maps) got. Still it gives a good snapshot of the neighborhood in most cases," says Leigh Sims, Sightline's spokesman.

For a fast-growing city like San Jose, CA, for example, the map is void of, among other newer destinations, a major new and expanding community shopping center -- the first in decades for the downtown core of a city called the Capital of Silicon Valley. Still the nation's 10th largest city's downtown are earned an 83 Walk Score. Characteristics key to walkability aren't accounted for in the score including narrow streets, block length, topography, public transit, safety, aesthetics, pedestrian-friendly design, etc.

Walk Scorers say the Walk Score is merely a starting point.

To get a closer look at key walkability characteristics, users may want to bolster their finds with Google's Street View or other online mapping services that offer side-walk level views of certain metro areas.

Or they can actually hoof it around town.

Still, the latest tap into Google's maps is unique. It offers Walk Scores of celebrity locations including Bill Gate's remote estate (5); President Bush's distant Crawford Ranch (0); Seattle's Space Needle (88) and Boston's Fenway Park (97).

Here are the general guidelines for interpreting scores.

• Walker's Paradise: 90 - 100. Many can get by without owning a car.

• Very Walkable: 70 - 90. Possible to get by without a car.

• Some Walkable Locations: 50 - 70. Some destinations are within walking distance, but many everyday trips require a car.

• Not Walkable: 25 - 50. Most errands require driving.

• Driving Only: 0 - 25. Walk from your house to your car.

The Walk Score service also points out the benefits of walkable neighborhoods.

• Better health. Pedestrian-friendly neighborhood residents are leaner than those who live in the suburbs. Because they drive less they suffer fewer car accidents, a leading cause of death between the ages of 15 and 45.

• Less greenhouse gas. Car emissions are a leading cause of global warming.

• More transportation alternatives. Higher density leads to more public transit and bike lanes. Taking the bus is cheaper and safer than driving.

• More elbow rubbing. Walking boosts social capital by promoting face-to-face interaction with neighbors. For each 10 minutes a person spends in a daily car commute, time spent in community activities falls by 10 percent.

• Local business growth and strength. Density generates foot traffic businesses need to thrive, to create jobs and multiply.