A mapping startup called Mapzen has been working on an experimental map-visualization project called TransitFlow that provides us an animated look at 24 hours worth of transit-vehicle movement around San Francisco. Curbed points us to the project, which is headed (coincidentally) by an intern named Will Geary who's currently a grad student at Columbia University, and the effect of seeing all these buses and trains in motion is pretty soothing and hypnotic — and it's fun seeing the yellow BART trains shoot in from the Tranbay Tube and then seemingly disappear in the morass of other Market Street traffic.

Except for those late-night "OWL" buses, things go pretty quiet between 2 and 4 a.m., as you'd expect, but then watch as things ramp up and streets fill again with a reported 700 transit vehicles in the course of 24 hours — all sped up to fit in this two-minute video.

Here you can see the same treatment done to Mexico City and Chicago.

Traveling outside the city, the flow of mass transit becomes a whole lot easier to take in because of the dearth of options, as you can see in the animation below of the Bay Area and Sacramento. And, especially in those overnight hours, nothing is moving except those buses in SF.

As Geary says in a blog post, the map visualizations help us see what transit frequency looks like for the region — reinforcing the idea that people won't use transit as much when they know it's never coming at a certain hour. "Static transit maps provide geographic context but do not give any information about frequency," he says. "Timetables provide information about frequency but can be overwhelming, unintuitive and lacking geographic context. Perhaps we can use spatial-temporal visualization to combine the spatial information of a static transit map with the temporal information of a timetable, and make it easer to think and talk about transit frequency!"

Below, the even more comforting, much less chaotic visualization of the full Bay Area, set to Debussy's Clair de Lune.

Previously: Map Du Jour: SF Transit Stops, By Hashtag