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Mobility Monitoring – Roadways – Freeways
OVERVIEW • REGIONAL TRENDS • ROADWAYS • INTERSECTIONS • TRANSIT
BICYCLE/PEDESTRIAN • HOV LANES • TRAVEL DEMAND MANAGEMENT • PARK-AND-RIDE
Overview • Arterial Roadways • Crashes • Freeways • Performance Measures • Traffic Volumes
The Boston Region MPO monitors recurring congestion on freeways through collecting and analyzing speeds and travel times, and traffic volumes on highway segments and at all approaches to interchanges. (For the purposes of this website, freeways are considered the same as limited-access highways and express highways.)

Nonrecurring congestion due to incidents, special events, work zones, and weather is addressed by MPO member agencies through their respective and collective Incident Management Programs. Agency incident management data are not available at this time for monitoring and analysis. The freeway-congestion monitoring focus areas are described below.
Average Speeds and Travel Times
MPO staff collect and analyze speeds and travel-time data on limited-access highways in the Boston metropolitan region. This provides an understanding of which portions of the freeway system are hotspots for congestion. Maps indicating the changes in average speed on limited-access highways in the Boston metropolitan region between 1995 and 2005 will soon be available for download; in the meantime, similar maps showing the changes between 1995 and 2000 are available for download (at right).

Staff also determine the level of service (LOS) of freeway segments based on average travel speeds. As noted from the 1999–2000 monitoring period, about 20 percent of the monitored miles of limited-access highways experience LOS F (average speeds below 45 mph) during the peak travel periods. Another 23 percent of freeway segments experience LOS D and E (average speeds between 45 and 59 mph).

Average speed and travel time data that were collected in 2004–2007 are provided here by highway segment.
Traffic Volumes
MPO staff maintain a database of express highway traffic volumes for the Boston metropolitan region. From these data, detailed traffic-flow diagrams have been developed showing traffic volumes for all ramp and mainline sections of the express highways hourly from 6:00 AM to 10:00 AM and from 3:00 PM to 7:00 PM, as well as for average weekday daily traffic (AWDT). The peak-period traffic volumes are from the most recent year that ramps have been counted by MassHighway. AWDT volumes are from all years that ramp counts have been taken.

Peak-period and AWDT traffic-flow diagrams are presented here by highway segment. In each case, the year of the latest ramp counts is indicated. Staff used AWDT volumes to analyze congestion levels on express highways in eastern Massachusetts over the period 1970–2000, and projected to the year 2010. The results of this analysis, which show growth in traffic volumes and hours of congestion, are available for download (at right).
Interchange Performance
Freeway delays occur most frequently at interchanges, where traffic streams merge, diverge, or weave with each other. Congestion at interchanges is often related to high ramp volumes forcing their way into the mainline traffic, short weaving distances, inappropriate lane geometry at ramp merge points, or lack of adequate acceleration and deceleration treatments.

In evaluating interchanges, staff applied the following performance measures: the average daily traffic entering the interchange, the average observed peak–hour speeds, the posted speed limit for the freeway segments approaching the interchange, the crash rate, and crash severity. Analysis indicates that an interchange´s level of congestion is closely related to crash rate and crash severity. Results of the interchange data collection and analysis are available for download (at right).
Incident Management
Nationally, about half of all congestion can be attributed to nonrecurring causes, such as crashes, disabled vehicles, work zones, adverse weather conditions, and planned special events.

Several MPO member agencies and the City of Boston operate incident management programs to minimize the impacts of congestion-causing events. The Traffic Operations Center of the Massachusetts Highway Department employs Intelligent Transportation Systems (ITS) technologies to respond to incidents on limited-access highways. The Massachusetts Turnpike Authority operates its Operations Control Center to monitor traffic and respond to incidents. The City of Boston´s Traffic Management Center monitors traffic in real time, allows for the adjustment of traffic signals to alleviate problems, and supports the emergency responses to incidents.

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