TRAFFIC VOLUMES AND CONGESTION LEVELS ON LIMITED-ACCESS HIGHWAYS
in the Boston Metropolitan Region

This analysis, which uses a method based on average weekday traffic (AWDT) volumes, is used to identify portions of the network that experience recurring congestion.

The figures on this page display the AWDT volumes and congestion levels for the limited-access highways in the Boston region. In the figures, the bandwidths for the various sections of highway are directly proportional to AWDT volumes—the thicker the bandwidth, the higher the volume of daily traffic. Congestion level is defined for this analysis as the ratio of the AWDT per lane to the empirical threshold of 20,000 vehicles per day per lane. The colors indicate congestion levels, with green representing noncongested traffic and dark red representing congested (saturated) conditions.

Presented below is the diagram for the year 2000 measure of daily traffic volume and congestion. Many of the region’s limited-access highways are routinely congested for some amount of time during the peak commute periods, because their daily volumes exceed their capacity to handle the amount of traffic.

Daily Traffic Volumes and Congestion Levels on Limited-Access Highways in Eastern Massachusetts: Year 2000

 

A historical look at these two measures is presented in the figure below. It shows that by 1970, virtually the entire present-day regional limited-access highway system was in place, but that very little of it was experiencing serious congestion. Before 1970, congestion was occurring primarily on I-93/Southeast Expressway and the Central Artery. During subsequent years, congestion spread throughout much of the system.

Daily Traffic Volumes and Congestion Levels on Limited-Access Highways in Eastern Massachusetts: Years 1970–2000