E.g. take the first graph: the red surface starts at 0 and the upper bound is the actual 'overall ridership' for Second Avenue, right? (note to author: even when the units seem obvious to you, they might not actually be obvious for everyone). So the lower bound of the green surface (Lafayette Street) has the same shape as the data for Second Avenue. Why? What does that mean? It's just the upper bound of the green surface which is the actual data for Lafayette street, no?
On topic: glad to see bicycle usage is rising, but would be interesting to see if e.g. car usage is declining and how the total number of people on the road is changing.