This visualization is about the data of bike share station usage of Indego, which is a public bicycle sharing system that serves parts of Philadelphia at over 100 stations.
The purpose of this visualization is to help people to plan their commutes and avoid the busy hours in local bike stations.
As is shows, the x-axis represents different time within a day. The Y-axis is more complex, which represents the percentage of time the station is full or empty during that moment.
The graph itself only using a mark and two channels, with the mark of area and the channels of Color and Color saturation. However, the using of channel might no appropriate here. it might confuse people as it using deeper red to represents there are more bikes available. Because in our daily life, the color red always represents the signal of congestion or insufficience. Also, it lacks information density. For example, it could not present the difference in bike usage in each day within a week.
In fact, the author creates this graph because he thought his inital visualization is imperfect. But I don’t think so after digging out it. Here is his previous visualization.
Reference:
http://www.randalolson.com/2015/09/05/visualizing-indego-bike-share-usage-patterns-in-philadelphia-part-2/
http://www.randalolson.com/2015/07/18/visualizing-indego-bike-share-usage-patterns-in-philadelphia/