Walk Score, a website that helps apartment renters and home buyers to find neighborhoods where they can drive less, ranked U.S. city transit systems based on residents' access to public transportation.

New York, San Francisco, Boston, and Washington, D.C., top the list, while cities such as Houston, San Diego, Las Vegas and Columbus, Ohio are among the cities in the bottom half of the ranking.

Walk Score's first ranking of U.S. city transit systems (rated by its Transit Score index) reveals which cities offer residents the best access to public transportation. Transit Score, a national, quantitative rating of access to public transit, measures how well a location is served by public transportation and is based on data released in a standard open format by public transit agencies.

Transit Score measures how well a location is served by public transportation on a 0-100 scale. Places with scores of 70 or higher are considered to have excellent transit, places with scores between 50 and 69 have good transit, and places with scores below 50 offer some or minimal transit.

To calculate a Transit Score, Walk Score assigns a "usefulness" value to nearby transit routes based on frequency, type of route and distance to the nearest stop on the route. City scores are then calculated by applying the Transit Score algorithm block-by-block throughout the city and weighting the scores by population density. Detailed methodology information is available at www.walkscore.com/methodology.shtml.

Cities taking the top five rankings are:

(1) New York (Transit Score: 81)
(2) San Francisco (Transit Score: 80)
(3) Boston (Transit Score: 74)
(4) Washington, DC (Transit Score: 69)
(5) Philadelphia (Transit Score: 68)

Click here to find your city, neighborhood and home's Transit Score.