Here's a hind, which A2K-Bostonian is to blame for the daily traffic chaos ...

The dark blue on the map shows the neighborhoods whose residents spend the most time stuck in traffic. The red outlines identify 15 census tracts whose drivers disproportionately clog traffic, because they all tend to travel on the same small number of roads at the same time. When commuters from these census tracts clog the roads, the congestion ripples throughout the entire metro area, making everyone’s commutes longer.


Source and full report in the 'Boston Globe