INTERCHANGE ANALYSIS: Bottlenecks and
Congested Segments on Limited-Access Highways

Much like arterial roadways, where bottlenecks and delays are usually found at signalized intersections (and at intersections with other controls), limited-access highways tend to have delays at locations where traffic merges, diverges, or weaves, or where vehicles change lanes frequently. These locations include points of lane discontinuity (where traffic must merge due to a lane reduction) as well as interchanges.

This analysis focuses on interchanges, where high ramp volumes, short weaving distances, inappropriate lane assignments at direct ramp merge points, and lack of appropriate acceleration and deceleration treatments often cause delays and lengthy queues.

The table below presents the following interchange characteristics: average daily traffic entering the interchange, average observed peak-hour speeds, expressway design characteristics, and safety parameters. These characteristics are listed together to highlight congestion and safety conditions.

The analysis indicates that interchange bottlenecks, crash rates, and crash severity are closely correlated. Some of the most congested and crash-plagued interchanges include: I-95/Route 128 at Route 1 in Lynnfield/Peabody, Route 1 at Route 129 in Lynnfield, Route 1 at Route 60 (Copeland Circle) in Revere, Route 1A at Route 60 and Route 16 (Mahoney Circle) in Revere, Storrow Drive at Fenway/Charlesgate in Boston, I-93 at I-95/Route 128 in Woburn, I-90/MassPike at I-95/Route 128 in Weston, I-93 at Route 38 (Mystic Avenue) in Somerville, and I-495 at I-90/MassPike in Hopkinton/Westborough.

Click Here for Table: Analysis of Interchanges on the Limited-Access Highways

Click here for a discussion of Traffic Volumes And Congestion Levels On Limited-Access Highways