The Inman Square “Peanutabout” – Birth of an Innovative Design Solution

By Steven Bercu



Just imagine: instead of gritting your teeth as you attempt to navigate the vehicular minefield that is present-day Inman Square, you could soon be circulating pleasantly along the rim of a traffic-calmed motoring peanut, a point of genuine interest lending harmony to this key crossroads.   

Such a design could radically improve traffic flows, safety, and the community fabric of crash-prone Inman Square.  The “Peanutabout” would combine three distinct elements: mini-roundabout-style geometry, which the Federal Highway Administration recommends for built-up areas; a compressed or peanut shape in lieu of the more traditional circle, to accommodate the unusual dimensions of Inman Sq., and best-practices bikeways of the sort employed in conjunction with Dutch roundabouts.  Here is the story of the origin of this innovative design direction and how it has evolved to date.



Inman Square, in Cambridge, MA, a byproduct of the Colonial-era cowpaths and ancient Native-American byways that eventually translated into greater Boston’s road network, has long been a crossroads of danger, confusion, and fear.  Two major arterials, Cambridge St. and Hampshire St., intersect at an oblique angle, the lengthy mixing zone a flat expanse of indeterminacy and chaos.  No fewer than three additional cross streets transact the intersection, creating a welter of unexpected turning movements and adding to the atmosphere of uncertainty.  Pedestrians desiring simply to cross the intersection must undertake a lengthy journey of dog-legged detours.  Buses and trucks make regular use of the intersection, while a firehouse flanks its southern edge.  Finally, Hampshire St. (which changes its name to Beacon St. at the Somerville line) is believed to be the busiest bicycle-commuting corridor in Massachusetts, with bicycle use set to grow further following the implementation in 2017 of protected bike lanes along portions of the Beacon St. corridor. Inman Square has long been a known hotspot for bicycle crashes – with 69 total crashes between 2008 and 2012 (15 bike) the intersection of Cambridge and Hampshire Streets was flagged by MassDOT as exceeding the statewide average crash rate.

While there have been numerous proposals over the years to improve traffic flow and safety in Inman, a satisfactory design solution has remained stubbornly elusive.  In 2016, Cambridge (not for the first time) initiated a public process to seek design improvements for Inman.  Other than one or two public meetings and some preliminary renderings from an engineering consultant, this process made little headway prior to the tragic crash in June 2016 that killed 27-year-old Amanda Phillips as she bicycled away from Inman Square.  One outcome of this tragedy was to refocus and reinvigorate the search for design solutions that could truly ameliorate road safety conditions across Inman’s ticking time bomb of crossings, signals, and turning movements.



The City of Cambridge asked its engineering consultants to focus on two potential solutions, a “Bend Cambridge St.” option and a “Bend Hampshire St.” option, which it presented to the public at a joint meeting of committees of the City Council in mid-July.


The “Bend Hampshire” option


The “Bend Cambridge” option


We at the Boston Cyclists Union saw significant flaws with both of these proposed solutions.  Bending Hampshire would necessitate a three-stage process to traverse the intersection along a bicycle-priority corridor, resulting in both major inconvenience and potential new dangers for bicyclists.  While Beacon Street in Somerville already boasts one of the highest rates of cyclists (potentially THE highest rate) in the region, the numbers are only going to increase after the Beacon Street cycle track is complete, sending even more people through the intersection, across Hampshire, on bikes.  While the volumes of people biking deem bending Cambridge the “less bad” option of the two, it still lends itself to cyclists needing to take two turns in order to travel “through” to the other leg of the street.  It also necessitates a left turn to exit from the heart of the intersection, which could make people on bikes even more vulnerable (while the bend Hampshire requires a left to turn into the intersection, but a right takes you out and back on track).  Additionally, while the City of Cambridge’s desired outcomes are separation for bikes, that will not be possible with left-turns and will expose people biking to more danger.



In July 2016,  Anne Lusk, a prominent bicycle advocate and a researcher at the Harvard T.H. Chan School of Public Health with a background in environmental architecture, approached the Boston Cyclists Union about the possibility of pursuing either a peanut-style roundabout or double-roundabout solution for Inman Square.  This cute video, produced for a project in Boise, Idaho, is suggestive of how such a roundabout could work.

Dr. Lusk put the Bike Union in touch with Kittelson & Associates, an engineering firm that has been at the forefront of roundabout research, design, and implementation in the U.S. for many years and led the publication of the first and second edition of the FHWA Roundabout Guide and has contributed to the state of the practice for bicycle design in the U.S. through contributions to the NACTO Urban Bikeway Design Guide and FHWA’s Separated Bike Lane Planning and Design Guide.  A three-way discussion ensued and in August, the Bike Union, with funding from a Helen & William Mazer Foundation grant, hired Kittelson to do a feasibility assessment and preliminary design for a peanut-style roundabout solution for Inman.  

We were quite excited when Kittelson’s analysis concluded that such a roundabout could be accommodated in Inman, and we realized that we could have a part in promoting a first-of-its-kind (for the U.S.), European-inspired roundabout solution that unravels the gordian knot of Inmania.  We worked with Kittelson to optimize the design for a roundabout that would feature elevated cycle tracks along its perimeter, and Kittelson’s initial rendering looked like this:


In mid-September, Bike Union executive director Becca Wolfson and representatives of Kittelson met with City of Cambridge staff to present our findings regarding the feasibility of the peanut design and the conceptual rendering for it.  The City had considered and rejected as infeasible a roundabout solution for Inman, but had not considered a peanut-style mini-roundabout.  The staff were favorably impressed and have since indicated an interest in including this roundabout approach alongside the “Bends” solutions as the pubic process moves forward.  

The design continues to evolve and enliven.  See this lively rendering of the design by landscape architect Elena Saporta:



We at the Boston Cyclists Union are excited about a design direction that holds the potential not only to cure many of Inman’s traffic woes, but to yield a truly inspiring public space that reimagines Inman Square for the future.  



The advantages of the roundabout solution being proposed by the Boston Cyclists Union and its consultant, Kittelson & Associates, include:

  • Traffic moves steadily through Inman, but at a calmed speed, creating a lower-stress, more pedestrian- and bicycle-friendly environment.
  • Fewer conflict points and slower speeds than the current intersection.
  • Simplifies and eases pedestrian crossings via crossing islands and raised crosswalks
  • Bicycles can move through the Square with minimal or no stopping and minimized deflection.
  • The design creates a new pedestrian crossing directly across the heart of the Square.
  • By elevating the cycle tracks and using European-style protected crossings, those traveling by bicycle will be much more visible to drivers; oblique or unexpected crossing angles are completely eliminated.
  • Incorporates “mini roundabouts” being touted as a safer option by Federal Highway Administration for urban areas.
  • Achieves sufficient throughput to manage motor-vehicle operations on Hampshire and Cambridge Streets.
  • Shorter queues for motor-vehicle traffic.
  • Accommodates fire trucks and large trucks via mountable curbs and traversable central islands.
  • Maintains direct access to all adjacent streets for fire trucks.
  • Brings back the functionality of turning left from any one street approach to another — none of which are currently allowed, by people biking or driving.
  • It gives Cambridge the chance to be a leader and innovator by installing a first-in-the-nation roundabout with protected bike lanes — something we have yet to see implemented in the U.S.!

In sum, the design can provide a safer, more comfortable environment for all modes and users of this busy Cambridge crossroads. It encourages slow speeds, manages conflict areas to discrete locations, and creates a public realm for neighborhood residents, businesses, and visitors to enjoy.


***If you want to learn more about the engineering behind the Roundabout and share any of your own ideas and thoughts about how to improve Inman Square and specifically this roundabout design, we invite you to join us on Thursday, December 8th for a design charette!

December 8th, 6-8pm
Hosted at PCA Architects, 221 Hampshire Street, Cambridge

RSVP and get more info at the facebook event, linked here!


  1. mark chase on November 30, 2016 at 11:47 am

    I like the peanut but there is one big trade off and that is isolating the potential public space in the middle of the road where it’s not so useful. BTW, probably the worlds most famous peanut is in Poynton, UK:

  2. Nicholas Shectman on November 30, 2016 at 12:05 pm

    Speaking as someone who has biked through this intersection six thousand times:

    I’d be concerned that a cyclist following the green path westbound (on either Hampshire or Cambridge) through this intersection would find themselves to the right of an inbound 91 bus and get squished by the tail end of the bus encroaching on the bike lane as the bus makes the tight right turn entering the intersection from Springfield St.

    I’m also confused that you use ease of bike access as a reason to reject the otherwise quite safe “Bend Hampshire St” option and then replace it with one that’s considerably more serpentine for both bikes and buses. Do you imagine that cyclists heading through this intersection will really detour all the way to the crosswalks in your renderings? Even if they did, would Hampshire bike traffic be safer conflicting twice with right-turning traffic from Cambridge to Springfield or Antrim, when currently they don’t conflict with that traffic at all?

  3. Rozann Kraus on November 30, 2016 at 4:36 pm

    and it’s non-allergenic.

  4. Matthew on November 30, 2016 at 5:57 pm

    I like the concept and I think there’s merit in developing it further. But I immediately spotted several problems with the geometry of the layout in the main diagram at the top. I hope that these can be fixed.

    The first and most major one is where the cycle lane meets a Zebra crossing and suggests that the person cycling can turn left onto the Zebra crossing. The problem with this arrangement is that there could be a car being driven approximately 2-3 feet to the left, and the driver of that car would have no time at all to react to a person cycling and turning left onto the Zebra crossing. Normally, in the Netherlands, in modern roundabout design, there is a clear lead-in lane to the crossing so that drivers can clearly see, directly in front of them, when a person cycling is about to enter the cycle-priority crossing. That element seems to be missing from this peanut design. To fix that would require creating more separation between the cycle lane and the driving lane.

    The other major geometry issue I noticed is that the exits of the “peanut” are too gently curved. Roundabouts are supposed to be traffic calming devices and reduce speeds using their design. But I would be worried that on the drive from say Cambridge Street to Hampshire Street it would be too easy for drivers to build up significant speed — only to blow through the Zebra crossing at Hampshire Street. There’s not enough deflection.

    There’s also some minor awkwardness with the geometry around Antrim Street where it seems to be placed too closely to the entrance from Cambridge Street. Elena’s design actually handles that well by making it only possible to turn from Cambridge onto Antrim, and not from any other arm.

    P.S. Minor note: the roundabouts you seem to be discussing are not “mini-roundabouts”. Mini-roundabouts are a term from the UK where they are used extensively (basically, wherever Americans would put a 4-way stop, British put a mini-roundabout instead). A mini-roundabout, a term that was invented by the British, is a roundabout without a centre island but instead only has a painted circle in the middle. They are easy to fit into a small junction. But, to put it simply: they are rather useless. Drivers will almost always drive straight over the centre paint even though it is technically illegal to do so. The term you probably want to use is “small roundabout” which is a roundabout with a small island, not merely some paint on the roadway surface.


  5. John-Mark Palacios on November 30, 2016 at 9:49 pm

    First of its kind in the US? That depends on whether our 5 leg peanut-about gets built first here on Kauai. 😀 This looks like a good concept, though.

  6. Harriet on November 30, 2016 at 10:19 pm

    Roundabouts are notoriously dangerous in the Boston area. I have drrven in the UK and roundabouts there are wonderful. In Boston they are scarey at best and quite dangerous. Look at Powder House Square, and the peanut roundabout on Rt 16 in Cambridge, both dangerous intersections.

    We need to educate drivers and riders. Common curtesy would go a long way for most drivers. I see many bike out after dark with no lights.

    Perhaps start to ticketing moving violations like lane changes without signalling, cutting off other motorists etc.

  7. Caitlin McMurtry on December 1, 2016 at 12:54 am

    Let’s say I’m on my bike heading southbound through the intersection on Hampshire Street, but I’d like to turn left and continue heading SE on Cambridge Street. From the map, it looks like I’d have to come to a stop in the bike lane, look over my left shoulder for traffic, wait for vehicles to pass or for a break in traffic (because cars in this design don’t come to a stop) and then make my way across both lanes and over to Cambridge Street, where I can make a right and head SE.

    If that’s correct and traffic is heavy, it seems like I’ll have three options:
    (1) I wait in the bike lane, blocking other cyclists until I can cross both lanes of traffic.
    (2) I hop up onto the sidewalk (so as not to block the bike lane) and wait for traffic.
    (3) I hedge over into the buffer zone, closer to moving cars, while I wait for a break in traffic.

    None of these seem like great options.

    Am I characterizing these moves correctly, or am I missing something. If this is a correct characterization, can you help me understand how this is preferable to some of the other proposed designs or a peanutabout that has mandated stops in certain places to guarantee breaks in traffic?

  8. Timothy Kukler on December 1, 2016 at 5:48 am

    Wish the trees weren’t there in the artist rendition. Cement shapes can be short and serve the same function to protect pedestrians and can be designed in pleasing shapes, are easily repaired and don’t otherwise require maintenance. Cement with rebar (shapes of various styles) is what many federal buildings choose.

    I like trees and all but we need more visibility, not less. Trees only look as good as artist’s renditions when they are young, but they really grow and are expensive to maintain by the city (and need replacement after a long time) and my big gripe is that their drooping branches reduce driver and pedestrian visibility unless meticulously and frequently maintained, a burden the city doesn’t need to incur. When it snows they are even worse.

    Thanks for reading.

  9. Today’s Headlines | Streetsblog USA on December 1, 2016 at 8:59 am

    […] Boston Plans Bike-Friendly “Peanutabout” to Make a Tricky Intersection Safer (Boston Cyclists Union) […]

  10. […] Tuesday, the Boston Cyclists Union shared the inspiring back story behind a new concept for the long, complex seven-way intersection created by the acute crossing of […]

  11. Doug Brown on December 2, 2016 at 3:30 pm

    Well done, BCU! Love this idea!!!!

  12. Dave Adams on December 3, 2016 at 10:09 am

    Harriet mentioned the danger of “Roundabouts” in Boston. The intersections she described are properly called “rotaries.” The difference between roundabouts and rotaries, as it was explained to me, is the angle of the entries and exits. As Matthew stated earlier, the exits in this design may be too gentle — they may encourage drivers to accelerate out of the peanut, ignoring pedestrians crossing and bikes continuing in the green paint. Forcing drivers to turn significantly into and out of the peanut should help immensely.

  13. […] Tuesday, the Boston Cyclists Union shared the inspiring back story behind a new concept for the long, complex seven-way intersection created by the acute crossing of […]

  14. Today’s Headlines – Streetsblog USA on December 5, 2016 at 3:55 pm

    […] Boston Plans Bike-Friendly “Peanutabout” to Make a Tricky Intersection Safer (Boston Cyclists Union) […]

  15. […] Tuesday, the Boston Cyclists Union shared the inspiring back story behind a new concept for the long, complex seven-way intersection created by the acute crossing of […]

  16. […] Boston Cyclists Union have been among the most vocal in pushing for solutions – most hoping for a peanut-shaped “roundabout” solution considered to offer more safety benefits, said Michael Davidson of Cambridge Bicycle Safety, […]

  17. […] Tuesday, the Boston Cyclists Union shared the inspiring back story behind a new concept for the long, complex seven-way intersection created by the acute crossing of […]

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