The Congestion Comparison by (Street) metric refers to the difference in minutes a street was congested in 2015 relative to 2012. Congestion occurs when flow is greater than road capacity.
The Congestion Comparison (zip) code metric is the weighted average of the street metric based on inter-street distance.
The Travel Time comparison (zip) metric shows the relative difference between average travel times in 2012 and 2015. These times were calculated from the link's speed and length.
Maps use traffic data from the Eastern Massachusetts road network recorded by INRIX. Speeds were captured in real-time using vehicle-probe technology (mobile phones, GPS sensors in fleet vehicles, connected cars and road-based sensors).