Cambridge Civic Journal Forum

December 1, 2016

A Peanut in Inman Square?

Inman Square is a difficult, pre-automotive, cramped, often congested, diagonal intersection. Thoroughgoing safety and traffic-flow improvements are not possible, short of tearing down buildings to create more travel space, or an expensive grade separation.

Anne Lusk, Visiting Fellow at the Harvard School of Public Health and a relentless advocate for on-street barrier-separated bikeways, has promoted a proposal for a “peanut roundabout” as a solution to the problems with Inman Square.

A grade separation was built long ago, farther west where Cambridge street runs between Harvard buildings. Though Lusk works at Harvard University, Inman Square does not adjoin the campus, and the political and financial resources of the University evidently don’t come to bear on the Square’s problems.

A Web page from the Boston Cyclists Union describes the “peanut roundabout” concept which Lusk is promoting for Inman Square. Here’s a conceptual drawing from the Web page:

"Peanut Roundabout" concept for Inman Square

“Peanut Roundabout” concept for Inman Square

I do think that the peanut roundabout concept is clever in itself. By eliminating traffic signals, this design might improve traffic flow.

— except for problems for bicyclists and pedestrians.

In the conceptual drawing on the page, to continue across the square in the same direction, bicyclists are directed to follow a circuitous route on separated bikeways, subject to right-hook risks, and turn sharply left after waiting at locations where they would block other bicyclists bearing right. There is no waiting area other than the narrow bikeway in which the bicyclists approach. The page describes the crossings as “European-style protected crossings” — but they aren’t. Strictly speaking, in traffic engineering, “protected” means that conflicting movements are prevented by traffic signals. No traffic signals are shown in the conceptual drawing. Four of the six crosswalks are raised, and these would slow motorists, but there are no waiting areas that would make it clear whether bicyclists will be turning across motor traffic or proceeding straight.

All in all, I cannot imagine how this concept would work for bicyclists or pedestrians without traffic signals for the crosswalks. Signals, though, would result in more motorists in the roundabout blocking other motorists’ travel in the roundabout. The conceptual drawing avoids raising this issue. Few vehicles are shown in the roundabout, inconsistent with the many in the connecting streets.

The conceptual drawing shows door-zone bike lanes leading to and from Inman Square at every approach. Earlier this year, cyclist Amanda Phillips was killed when the opening door of a parked vehicle flung her under a truck — the incident which led to calls for redesign of the Square. She was, however, not in the Square: she was had left the Square. (Identification of the crash location) It has been reported that she was exiting the sidewalk just before she was doored — so, she came from behind the vehicle whose door opened in front of her. What lessons from this crash have informed the proposed peanut design? Apparently none. The bike lanes shown at exits from the Square place bicyclists in the same hazardous situation as Phillips: emerging from behind parked vehicles, rather than where they might be visible with a driver’s-side mirror or a glance over the shoulder.

The page claims that “[s]uch a design could radically improve traffic flows, safety, and the community fabric of crash-prone Inman Square.” It would be useful in evaluating proposals, and claims like these, to have  a traffic capacity and flow analysis, and a crash study.  Instead, on the Web page, there is a list of claimed advantages, with no mention of potential problems and no analysis.

My overall impression of this design as a bicyclist, in addition to the concerns about safety, is that while it might increase appeal to bicyclists who are fearful of riding in mixed traffic, delays will be such that bicyclists who want to get where they are going will ride in the motor traffic. And let’s hope that they understand that safety would require them to ride in line with the motor traffic rather than keeping out of its way, as the designated routes strongly imply to be the key to safety.

The City of Cambridge has put forward two other proposals. A  “bend Cambridge Street” proposal is shown in the image below. Traffic on Hampshire Street would travel straight through, and traffic on Cambridge Street would zigzag. A similar “bend Hampshire Street” proposal is more or less a mirror image of this one. These proposals are similar to what has been done with Union Square in Somerville and at Lafayette Square (the intersection of Main Street and Massachusetts Avenue) in Cambridge.

City of Cambridge "bend Cambridge Street" proposal

City of Cambridge “bend Cambridge Street” proposal

The “bend” proposals include traffic signals and require bicyclists and motorists to make left turns. I do think, however, that the blue space in the “bend Cambridge Street” proposal might include bikeways, so  bicyclists on Cambridge Street could continue straight where the street bends left toward the first traffic light and then re-enter Cambridge Street by crossing Hampshire Street at the second traffic light rather than by turning left. (This would not be practical with the “bend Hampshire Street” proposal, because bicyclists would have to turn left across Hampshire Street to enter the blue space). The drawing below shows my proposal. Bicyclists would follow the red arrows.

Bend Cambridge Street proposal with shortcut bikeways

Bend Cambridge Street proposal with shortcut bikeways

The blue areas also might include useful social space — unlike the peanut roundabout proposal, where the extra space would be in the middle of the street.  The two traffic lights in the Bend Camridge Street proposal would, to be sure, increase delay for motorists. Bicyclists following the red-arrow route would encounter only one traffic light.

I’ll admit that I don’t have any more thoroughgoing answers to Inman Square’s problems other than the two I’ve already mentioned — tearing down buildings or creating a grade separation — which are not going to happen. I’ll be trying to think of other possibilities, and please, you do also.

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August 9, 2016

Cambridge InsideOut Episodes 163-164: August 9, 2016

Cambridge InsideOut Episode 163 (Part 1)

This episode was broadcast on Tuesday, August 9, 2016 at 5:30pm. The hosts are Judy Nathans and Robert Winters. [On YouTube]


Cambridge InsideOut Episode 164 (Part 2)

This episode was broadcast on Tuesday, August 9, 2016 at 6:00pm. [On YouTube]

References for tonight’s programs

June 29, 2016

Cambridge InsideOut Episodes 151-152: June 28, 2016

Cambridge InsideOut Episode 151 (Part 1)

This episode was broadcast on Tuesday, June 28, 2016 at 5:30pm. The hosts are Judy Nathans and Robert Winters. [On YouTube]


Cambridge InsideOut Episode 152 (Part 2)

This episode was broadcast on Tuesday, June 28, 2016 at 6:00pm. The hosts are Judy Nathans and Robert Winters. [On YouTube]

Much of the discussion in both episodes was motivated by the recent death of cyclist Amanda Phillips in Inman Square and the concurrent proposals by the City of Cambridge to modify the traffic patterns in Inman Square.

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