Boston Bus Speeds - Visualized

From Bostonography.com, we have this excellent near real-time take on bus speeds in Boston, based on GPS data.  Well, technically speaking, its either GPS data from the past 3 hours, or the full 24 hours of data from the previous day.
From the description

This map is based only on the discrete location reports from buses, which occur at regular intervals. This means that speeds are calculated based on straight-line distances between those points, not on the actual distance traveled by the buses. In some areas, therefore, speed is a little underestimated because the bus followed actual crazy Boston streets, not that straight shortest-distance path. Note also that the speeds are overall averages that include stops, not solely moving speed.

The below is just a screen-grab, go to the original for the live version.