Walk Score has ranked the 25 largest US cities by the usefulness of their transit systems. New York sits at the top of the list released by the website, which otherwise provides its users with information about the most walkable inner-city neighborhoods. San Francisco came second in the public transit rankings, with Boston, Washington, D.C. and Philadelphia rounding out the top five.

Walk Score used a method it calls Transit Score to rate city transit systems on a nought-to-hundred scale. The Transit Score is dependent on the "usefulness" of routes in a city, which is quantified by a combination of the proximity of a point to the nearest stop on a route, the frequency of the route and the type of route.

A raw Transit Score is calculated block by block by summing the value of all nearby routes, which are then weighted - with rail services deemed preferable to ferries and cable car/trams, which are preferable again to bus routes. Blocks are also weighted by population density so that areas with more people living in them have a larger effect on the score. This data is normalized to make a comparable score of between zero and 100, calibrated against a notional "perfect score" location based on the average of five city centers where full transit data was available.

The ability to assign a city a Transit Score is dependent on that city publishing data in the GTFS format, so this is the 25 largest cities that make such data available, with Atlanta and Phoenix among the large cities identified by Walk Score is keeping its public transit data under wraps.

The Transit Scores of the 25 ranked cities are as follows:

1. New York (81)
2. San Francisco (80)
3. Boston (74)
4. Washington, D.C. (69)
5. Philadelphia (68)
6. Chicago (65)
7. Seattle (59)
8. Miami (57)
9. Baltimore (57)
10. Portland (50)
11. Los Angeles (49)
12. Milwaukee (49)
13. Denver (47)
14. Cleveland (45)
15. San Jose (40)
16. Dallas (39)
17. Houston (36)
18. San Diego (36)
19. San Antonio (35)
20. Kansas City (34)
21. Austin (33)
22. Sacramento (32)
23. Las Vegas (32)
24. Columbus (29)
25. Raleigh (23)

Interestingly, Walk Score classifies scores of 90-100 as "world class," 70-89 as "excellent" and 50-69 as merely good. That being the case, Walk Score's ranking included no world class transit systems, and only three that are excellent. These include San Francisco, whose transit system Walk Score describes as "dense and uniform," and Boston, which Walk Score notes has commuter rail lines "stretching in all directions."

With a score of only 23, Raleigh falls into Walk Score's lowest band, named "minimal transit."

Source: Walkscore (rankings, press release PDF, blog post), via Treehugger