One of my scientific heroes and seminal teachers is Professor Frank Kelly at Cambridge. What a pleasant surprise to see his involvement in a data visualization project. To cite his wise words:
The travel-time maps are more than just pretty to look at; they also demonstrate an innovative way to use and present existing data. We are entering a world where we have access to vast quantities of data, and ways of turning that data into information, often involving clever ideas about visualisation, are becoming more and more important in science, government and our daily lives.
The little black dot near the center of the map indicates the Mathematics building at Cambridge. The contours (vaguely visible at our scale) represent intervals of 10 minutes by public transportation away from the black dot. Any colored dot on the map refers to the time at which a traveller must leave in order to get to the Math building by 9 am, taking into account traffic situation, time of day, and decisions. The hope of such maps is to help commuters (by public transit) plan their travel.
Professor Kelly has a very nice write-up on the intricacy of generating the data for such a map, which includes techniques of sampling, smoothing, extrapolation and so on. It is rare that we get insights into the chart-making process. He also carries a larger version of the travel-time map.
A similar article can be found at Plus magazine.