Strava, a popular app used to log routes and times for cyclists and runners, has an an interactive heatmap of 77 million rides and 19 million runs recorded by users over the past few years. It is made up of more than 220 billion total data points, and it is amazing.
Red lines show especially highly-used routes, followed by dark blue lines, then light blue. The map is remarkably detailed, allowing you to zoom in to an individual street and see which lane bikers traveled in most often. It shows which paths and streets are clogged with users and which are curiously overlooked.
Strava is mainly used by competitive exercisers looking to improve their times and beat others', so this isn't a picture of bicycle commuting or casual walking. But as a whole, it's the most comprehensive picture of recreational biking and running we have.
Take a few minutes to explore the interactive map, or check out selections of some of the country's biggest cities, below.
San Francisco and Oakland
Minneapolis and St. Paul
The map also shows a few curious patterns that don't have an immediately obvious explanation.
For instance, most routes are confined to individual cities, but there's a distinct band across the southern part of Iowa, from Omaha to Fort Madison.
As it turns out, that was the 2013 route for RAGBRAI — an annual ride across Iowa that's the largest bike touring event in the world. As riders made their way across the state, a good number of them must have had Strava logging their routes and times.