Large US cities are notorious for traffic congestion, and Boston is no exception. But not all congestion is the same. A bottleneck (or choke point) is different from a traffic jam, for example. Unlike congestion caused simply by heavy traffic volumes, a bottleneck is a recurring disruption of traffic at the same location in a roadway, which is usually caused by a specific physical condition—such as, the road design, abrupt changes in alignment, lane drops, merges and diverges, badly timed traffic lights, sharp curves; or other physical constraints that can make a roadway unable to handle the volume of traffic it receives...