Visualizing Bus Route Congestion
This map is based on GPS data provided by the MBTA. The road segments in red are where buses can be found a disproportionately large amount of the time, suggesting that this is where they travel slowest.
Details
Each route is divided into road segments that are 300 feet long. Every five to ten minutes, we use the MBTA API to figure out where all of the currently running buses are. Each bus is matched to the nearest road segment on its route. Over time, we keep track of how many buses have been matched with each road segment. The segments that get matched with a "high" number of buses are considered high-congestion road segments.
We determine whether a road segment has been matched with a "high" number of buses by comparing it to other road segments from the same bus route. If a segment gets matched with a large number of buses—a number well above the mean for its route—than it has been matched with a high number and it will probably be colored red.
The exact cutoffs between the colors are based on quantiles calculated using road segment numbers from all routes. A road segment that is in the 80th percentile in terms of its deviation from the route mean (when compared to road segments on all routes) will be colored red.
The graph shows how the number of buses matched with each road segment is distributed across the road segments for the selected route.