The website Walk Score publishes not only walk scores, but also public transit and bike scores for select cities. The scores represent the accessibility of goods and services without the use of a car. I was curious to see if there was a correlation between a city’s walk, transit, and bike scores, so I generated a type of line graph to investigate the relationships, as well as a correlogram.

The line graph is designed to compare scores for some of the largest cities in the USA; line thickness is relative to city population. This group includes the 20 largest cities by population for which all three scores are reported – many of the nation’s largest cities (e.g., Phoenix, AZ; Jacksonville, FL; Indianapolis, IN) do not have a transit or bike score yet. The graph allows for the comparison of cities across a single mode of transportation, but also includes a sort of slopegraph at the transitions between transportation modes, highlighting the relative strengths and weaknesses of each city. The color coding is based on geographic clustering. From this, we can see that northeastern and northwestern states tend to have higher scores, while California and Texas tend to have lower scores. There is no obvious relationship between population and accessibility.

The correlogram doesn’t give any insight into specific cities, but it does provide a much clearer sense of the correlation between scores (and population). With this graph, we can see that walk and transit scores have the strongest positive correlation. Walk and bike scores are slightly less correlated, and transit and bike scores are the least correlated, though they still show a statistically significant positive correlation. City population, however, it not well correlated with any of the accessibility scores; the size of a city does not guarantee that you’ll be able to walk, bus, or bike to a decent coffee shop!

Data source: www.walkscore.com (One of my favorite websites – check it out!)