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.
OTHER PROPOSED SOLUTIONS
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.
A TOUGH NUT TO CRACK
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.
ADVANTAGES OF THE PEANUT
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!