All four categories were weighted equally, which doesn't make sense to me. If we are talking about 'Green', this doesn't account for the CO2 emissions from burning so much extra gas from being stuck in traffic, nor does it account for the acreage of parks, and potential CO2 those may have. In fact, a large portion of the cities at the top are college-based cities, meaning most bikers / commuters are probably college students and not necessarily residents.
Going further, it seems like they are changing how they measure with every column. Parks looks like it's a greater number is better (with no accountability towards size) or implication that the parks that do exist are not just concrete jungles. Gallons of fuel is just a volume measurement -- which is better? higher or lower? Percentage of population is fishy because they are mostly college towns, or areas that are known to have substantial poor populations who can only take the bus; this doesn't mean they are attempting to push people and infrastructure to be more green (results matter, not cities declaring green initiatives).
I'm just saying, data can be made to look however you want it to, and these four categories cannot be equally weighted, since they are measuring completely different things. I couldn't find the methodology used to rank these cities, which throws yet another red flag into it; My guess is they took the positional ranking for each city in each category and then average them out for a city to come up with a meta-score that was used to rank the cities. Who knows. I'd like to.