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How Boston Plans to Cool Down Streets Amidst Rising Temperatures

side by side maps of Boston showing daytime air temperature and nighttime air temperature on a blue to red scale

Temperature comparison across different Boston neighborhoods in the daytime vs nighttime based on modeling conducted as part of Boston’s Heat Plan. Courtesy of the City of Boston.

The City of Boston has several projects in the works as part of an ongoing Climate Ready Boston initiative in response to the changing climate patterns we’ve been experiencing and which are only expected to increase in frequency and severity, but the projects seem to miss a key connection between heat and transportation.

The City of Boston has released a new action plan to help the city cope with increasingly hot summer temperatures, but although the plan acknowledges how much wide streets and parking lots absorb heat to contribute to sweltering temperatures – especially in the city’s poorest neighborhoods – it offers only a few recommendations to make the city’s streets cooler with less asphalt. 

Boston’s new Heat Resilience Solutions for Boston report, otherwise known as The Heat Plan, is an action plan to prepare for the near-term and long-term impacts of extreme heat in a changing climate. 

It includes an in-depth view of five Environmental Justice neighborhoods in Boston that  experience the hottest temperatures – Chinatown, Dorchester, East Boston, Mattapan, and Roxbury – as well as recommendations “to advance heat resilience across Boston.”

Rising temperatures and the availability of shade from mature trees is becoming an increasingly pressing priority in how cities design streets. Last year, the City of Boston canceled a $25.6 million construction contract to rebuild Melnea Cass Boulevard in Roxbury after neighbors protested the project’s proposed removal of at least 121 mature trees.

In the Heat Plan, people reported a lack of trees and the presence of "lots of pavement, concrete and asphalt" as the top two reasons for why their neighborhoods feel hotter. 

Meanwhile, other aspects of the city’s climate change policies – namely the goal of reducing car traffic by roughly 50 percent under the GoBoston 2030 plan – could offer an opportunity for the city to convert acres of heat-absorbing asphalt with neighborhood-cooling gardens and tree plantings.

StreetsblogMASS reached out to Boston’s Department of Environment, the folks behind the Heat Plan, to ask how they’re coordinating with the Public Works and Transportation Departments to create more space for trees on city streets.

Reverend Mariama White-Hammond, Chief of Environment, Energy and Open Space, responded that “Boston’s trees beautify our communities, create oxygen, and mitigate the urban heat island effect while functioning as carbon sinks, and cleaning pollution from our air. We know that Boston’s history of disinvestment has led to inequitable access to trees. The City is committed to protecting and enhancing our tree canopy with an equity lens to ensure everyone can benefit from this public good.”

The Heat Plan lists 26 city wide heat resilience strategies; of these, three are listed under “Transportation and Infrastructure,” and two mention streets (the third infrastructure strategy focuses on the energy grid).  

A “Cool Commutes” strategy makes reference to the nearly half of Boston workers who get to work by transit, walking or biking and states that “well-coordinated implementation with the state and related City departments is critical to integrating cool commutes with planned transportation improvements for redesign and reconstruction projects and ongoing improvement programs.” 

Unfortunately, the next steps under this strategy only suggest a bus stop design challenge. This is despite acknowledging that cool commutes go beyond shade at a single bus stop and must also include the trip to and from the stop.

The second of the Transportation and Infrastructure strategies, “Cool Main Streets,” says it will use the Neighborhood Slow Streets initiative to incorporate cooling strategies such as “road diets and narrow lane widths that expand sidewalk dimensions to accommodate street trees and plantings.” 

Elsewhere in the plan, under zoning recommendations, the report references a City of Tucson, Arizona, standard that provides highly specific guidelines for pedestrian walkways.

Tucson’s rules require that “shade shall be provided for at least 50% of all sidewalks and pedestrian pathways as measured at 2 p.m. on June 21 when the sun is 82° above the horizon (based on 32°N latitude)." 

This may seem extreme, but we don’t have to wait until we reach Tucson-level temperatures before learning from their efforts. This kind of detailed standard could serve as a starting point in how the City of Boston embeds shade into transportation projects such as bike lane plans; having specific targets could serve as a leveraging tool to justify narrowing streets when needed.   

The Heat Plan also includes several neighborhood-level recommendations, and while many of them acknowledge the large role parking lots and roads play in how hot a place feels, the Plan’s recommendations are heavily skewed toward trying to add shade instead of reducing asphalt.

For instance, the plan points out that “many of East Boston’s hottest areas include large surface parking lots and parking structures with limited tree canopy,” but instead of tearing up some of that asphalt, the plan recommends adding shade canopies over the pavement. 

Another section of the report showed the results of a mathematical model that simulated  the neighborhood-level effects of different cooling strategies, like light-colored pavement and shade canopies. 

But the model did not consider the possibilities of replacing on-street parking areas or other asphalt surfaces with trees and gardens.  

Another City of Boston initiative relating to climate change resiliency is the Urban Forest Plan, which aims to “expand the urban forest both today and 20 years from now,” meaning increasing the number of trees in Boston. 

As part of the initiative, the City conducted an extensive tree inventory, labeling public trees and identifying 38,273 street trees in total. 

Slide from a March 2022 Open House presentation by the Boston Urban Forest Plan team showing canopy coverage, area covered by branches and leaves, as seen from above, across the City of Boston in 2019. Tree planting is being prioritized for areas with less than 10% of canopy coverage.
Slide from a March 2022 Open House presentation by the Boston Urban Forest Plan team showing canopy coverage, area covered by branches and leaves, as seen from above, across the City of Boston in 2019. Tree planting is being prioritized for areas with less than 10% of canopy coverage. Courtesy of the City of Boston.

In a March 2022 Open House presentation, the Urban Forest Plan project team shared that one of their plan’s goals is “the integration and accommodation of canopy expansion and providing adequate space for healthy trees into mobility efforts (from corridors to Complete Streets).” 

The presentation didn’t provide further details on the logistics or guidelines of how this integration would take place. The Plan was set to be released late spring 2022, but is not yet publicly available.  

Mayor Wu’s first budget included the following funds to help implement the Heat Plan:

  • $2.5 million for a new Climate Ready Streets program within Climate Ready Boston to deliver on heat resilience, stormwater management, and air quality on key transportation corridors 
  • $2.5 million of pandemic relief funds to grow and preserve our urban tree canopy, including an innovative pilot program on private land
  •  $137 million in capital funding, plus operating investments, to create and protect parks, the tree canopy, and open spaces in the city.  
rendering showing a bike lane, crosswalks, curb bump out
A rendering of the Cummins Highway reconstruction project showing different design elements including bike lanes, crosswalks, bus stops and lighting aimed to increase safety for all who use this street. Courtesy of the City of Boston.

Despite having no specific goals to increase the urban forest canopy or reduce the amount of asphalt that covers the city, Boston is making progress toward increasing the number of trees along streets at the individual project level. 

A Public Works Department project to redesign and rebuild Cummins Highway in the Mattapan neighborhood, one of the five Environmental Justice communities spotlighted in the Heat Plan, will add mobility features such as accessible sidewalks, safer crosswalks, and better bike lanes. Cummins Highway is currently four lanes wide; the new street will only be two lanes wide, with protected bikeways. 

Cummins Highway begins near Mattapan Square, one of the hottest areas in the neighborhood, then cools down as it approaches the greenery of the Calvary Cemetery near Roslindale.

The Cummins Highway project page references the Climate Ready Boston initiative’s goal to reduce urban heat and heat risk and presentation materials note how the narrower roadway will reduce the amount of heat-absorbing pavement in the neighborhood: 

tree lined street
Graphic from a Heat Resilience and the Cummins Highway Reconstruction presentation showing the factors that contribute to cooler streets in Boston. Courtesy of the City of Boston.

A Public Works spokesperson told StreetsblogMASS that "the Cummins Highway project is still in design, so the number of trees proposed along the corridor is still yet to be determined, but project designers hope to have over 100 planted." 

Another street redesign currently underway is Ruggles Street, extending from Tremont Street to Washington Street in Roxbury, another Environmental Justice neighborhood highlighted in the Heat Plan. 

When it’s complete later this year, the new Ruggles Street will feature a sidewalk-level bike lane in the northbound direction, and a buffered southbound bike lane, and several raised intersections. 

As of May, 11 new trees had been planted as part of the project, with 22 more trees scheduled to be planted in the fall, according to a Public Works Department official.

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