The various colors on the map represent the density of the population that uses public transportation to commute. You can click on a particular area to bring up a data box with detailed information, broken down by the percentages of residents who use public transport, cars, bicycles, or their own two feet. The detail also includes comparisons to national averages.
In a similar vein on the U.S. side, John Nelson, who mapped the various transportation methods used in and around the Seattle area, recently grabbed Bicycling.com’s top bike-friendly cities and mashed that data with census commuting data to create visualizations of commuter habits in each city:
Nelson placed a dot for every person in each city who commuted under foot power, either by walking or biking to work. He did express one lament in a blog post presenting the maps: “Unfortunately, the data recorded no distinction between bicycles and unicycles, so quirk-rich neighborhoods are obscured — for now.”