The following information is readable only to screen readers: Data for arterial congestion is available on the CTPS Data Catalogue. You can download the spreadsheet after following this link: Expressway Congestion Spreadsheet
Individual incidents of congestion, such as getting stuck in a traffic jam or waiting for a late bus, are frustrating. When congestion occurs regularly—at bottlenecks, work zones, crash sites, and during weather events—it can profoundly impact mobility, safety, air quality, and health. The Boston Region MPO’s Congestion Management Process is used to monitor traffic congestion on approximately 970 expressway miles and 1,200 arterial miles in eastern Massachusetts.
The Boston Region MPO monitors, analyzes, and develops strategies to manage congestion. One way to quantify congestion is to calculate the speed index, which is the ratio of observed speed to the posted speed limit on a roadway segment. This index compares ideal travel conditions to actual travel conditions. Roadway speeds are provided by INRIX, a company that collects vehicle probe data (global positioning systems [GPS] data collected in real-time from vehicles traveling on roadways). Congestion data that are on display on this dashboard was collected in 2012. For more information about these data, visit the Congestion section on the About page.
The speed index of arterial roadways in the Boston region is displayed in the graphic below. The speed index indicates congestion more accurately than travel speed alone because low travel speed may be a result of low speed limits on certain arterial facilities. Click on individual routes to explore the degree to which congestion slows travel on the Boston region’s many arterials during morning and evening rush hours. The AM peak period is between 6:30 AM and 9:30 AM, and the PM peak period is between 3:30 PM and 6:30 PM on arterial roadways. A value of 0.7 or lower is considered congested.