A report card for Mass. Ave.

Arlington has paid its consulting engineers to grade major intersections on Mass. Ave. The results of this standard traffic assessment can be found in pages 16–17 and 19–24 of the Functional Design Report.

The grades are based on seconds per vehicle of delay, whether from a signal or the geometry of the intersection and the flow of traffic.

This measurement is not really like an academic grade. There is no stigma attached to a C or even a D. Only grades E and F show unacceptable levels of service. Traffic normally entails waits, and as long as the waits are not excessive the intersection will pass this test.

An A at a signalized intersection may be a sign that the traffic signal is not warranted there; indeed, both the signals at Linwood-Foster and Thorndike-Teel score A grades, though the Town’s plan would retain these signals.

So, how did we rate?

Four of the studied intersections are unacceptable at rush hour today: Lake St. (F), Route 16 (E), and the unsignalized intersections (1) at Bates Rd. and Marion St. and (2) at Orvis and Grafton streets (both F). The report further notes (p. 20):

It is likely that many of the side street intersections along the corridor also experience long delays as well.

These single letter grades are a composite of separate grades for am and pm peaks, and each of those in turn comprises grades for each lane (through and turning). For instance, Lake Street earns an overall grade of F, yet the eastbound through lane on Mass. Ave. is rated a very adequate C during the evening peak.

See the functional design report for details, because this summary just scrapes the surface.

Update: The report also describes how the redesign would improve the levels of service for three of these bottleneck intersections.

Image reproduced with permission, thanks!


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