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    New visions for better transportation

    We typically experience transportation problems from the ground up. Waiting for a delayed bus, packing ourselves into a subway car, or crawling along in traffic, it is common to see such systems struggling at close range.

    Yet sometimes transportation solutions come from a high-level, top-down approach. That was the theme of the final talk in MIT’s Mobility Forum series, delivered on Friday by MIT Professor Thomas Magnanti, which centered on applying to transportation the same overarching analytical framework used in other domains, such as bioengineering.

    Magnanti’s remarks focused on a structured approach to problem-solving known as the 4M method — which stands for measuring, mining, modeling, and manipulating. In urban transportation planning, for instance, measuring and mining might involve understanding traffic flows. Modeling might simulate those traffic flows, and manipulating would mean engineering interventions: tolls, one-way streets, or other changes.

    “These are four things that interact quite a bit with each other,” said Magnanti, who is an Institute Professor — MIT’s highest faculty distinction — and a professor of operations research at the MIT Sloan School of Management. “And they provide us with a sense of how you can gather data and understand a system, but also how you can improve it.”

    Magnanti, a leading expert in operations research, pointed out that the 4M method can be applied to systems from physics to biomedical research. He outlined how it might be used to analyze transportations-related systems such as supply chains and warehouse movements.

    In all cases, he noted, applying the 4M concept to a system is an iterative process: Making changes to a system will likely produce new flows — of traffic and goods — and thus be subject to a new set of measurements.

    “One thing to notice here, once you manipulate the system, it changes the data,” Magnanti observed. “You’re doing this so you can hopefully improve operations, but it creates new data. So, you want to measure that new data again, you want to mine it, you want to model it again, and then manipulate it. … This is a continuing loop that we use in these systems.”

    Magnanti’s talk, “Understanding and Improving Transportation Systems,” was delivered online to a public audience of about 175 people. It was the 12th and final event of the MIT Mobility Forum in the fall 2021 semester. The event series is organized by the MIT Mobility Initiative, an Institute-wide effort to research and accelerate the evolution of transportation, at a time when decarbonization in the sector is critical.

    Other MIT Mobility Forum talks have focused on topics such as zero-environmental-impact aviation, measuring pedestrian flows in cities, autonomous vehicles, the impact of high-speed rail and subways on cities, values and equity in mobility design, and more.

    Overall, the forum “offers an opportunity to showcase the groundbreaking transportation research occurring across the Institute,” says Jinhua Zhao, an associate professor of transportation and city planning in MIT’s Department of Urban Studies and Planning, and director of the MIT Mobility Initiative.

    The initiative has held 39 such talks since it launched in 2020, and the series will continue again in the spring semester of 2022.

    One of the principal features of the forum, like the MIT Mobility Initiative in general, is that it “facilitates cross-disciplinary exchanges both within MIT and without,” Zhao says. Faculty and students from every school at MIT have participated in the forum, lending intellectual and methodological diversity to a broad field.

    For his part, Magnanti, who is both an engineer and operations researcher by training, embraced that interdisciplinary approach in his remarks, fielding a variety of audience questions after his talk, about research methods and other issues. Magnanti, who served from 2009 to 2017 as the founding president of the Singapore University of Technology and Design (with which MIT has had research collaborations), noted that the setting can heavily influence transportation research and progress.

    In Singapore, he noted, “They measure everything. They measure how people access the subway … and they use their data.” Of course, Singapore’s status as a city-state of modest size, among other factors, makes comprehensive transportation planning more feasible there. Still, Magnanti also noted that the infrastructure bill recently passed by the U.S. federal government is “going to provide lots of opportunities” for transportation improvements.

    And in general, Magnanti added, one of the best things academic leaders and research communities can do is to “continue to create a sense of excitement. Even when things are tough, the problems are going to be interesting.” More

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    Countering climate change with cool pavements

    Pavements are an abundant urban surface, covering around 40 percent of American cities. But in addition to carrying traffic, they can also emit heat.

    Due to what’s called the urban heat island effect, densely built, impermeable surfaces like pavements can absorb solar radiation and warm up their surroundings by re-emitting that radiation as heat. This phenomenon poses a serious threat to cities. It increases air temperatures by up as much as 7 degrees Fahrenheit and contributes to health and environmental risks — risks that climate change will magnify.

    In response, researchers at the MIT Concrete Sustainability Hub (MIT CSHub) are studying how a surface that ordinarily heightens urban heat islands can instead lessen their intensity. Their research focuses on “cool pavements,” which reflect more solar radiation and emit less heat than conventional paving surfaces.

    A recent study by a team of current and former MIT CSHub researchers in the journal of Environmental Science and Technology outlines cool pavements and their implementation. The study found that they could lower air temperatures in Boston and Phoenix by up to 1.7 degrees Celsius (3 F) and 2.1 C (3.7 F), respectively. They would also reduce greenhouse gas emissions, cutting total emissions by up to 3 percent in Boston and 6 percent in Phoenix. Achieving these savings, however, requires that cool pavement strategies be selected according to the climate, traffic, and building configurations of each neighborhood.

    Cities like Los Angeles and Phoenix have already conducted sizeable experiments with cool pavements, but the technology is still not widely implemented. The CSHub team hopes their research can guide future cool paving projects to help cities cope with a changing climate.

    Scratching the surface

    It’s well known that darker surfaces get hotter in sunlight than lighter ones. Climate scientists use a metric called “albedo” to help describe this phenomenon.

    “Albedo is a measure of surface reflectivity,” explains Hessam AzariJafari, the paper’s lead author and a postdoc at the MIT CSHub. “Surfaces with low albedo absorb more light and tend to be darker, while high-albedo surfaces are brighter and reflect more light.”

    Albedo is central to cool pavements. Typical paving surfaces, like conventional asphalt, possess a low albedo and absorb more radiation and emit more heat. Cool pavements, however, have brighter materials that reflect more than three times as much radiation and, consequently, re-emit far less heat.

    “We can build cool pavements in many different ways,” says Randolph Kirchain, a researcher in the Materials Science Laboratory and co-director of the Concrete Sustainability Hub. “Brighter materials like concrete and lighter-colored aggregates offer higher albedo, while existing asphalt pavements can be made ‘cool’ through reflective coatings.”

    CSHub researchers considered these several options in a study of Boston and Phoenix. Their analysis considered different outcomes when concrete, reflective asphalt, and reflective concrete replaced conventional asphalt pavements — which make up more than 95 percent of pavements worldwide.

    Situational awareness

    For a comprehensive understanding of the environmental benefits of cool pavements in Boston and Phoenix, researchers had to look beyond just paving materials. That’s because in addition to lowering air temperatures, cool pavements exert direct and indirect impacts on climate change.  

    “The one direct impact is radiative forcing,” notes AzariJafari. “By reflecting radiation back into the atmosphere, cool pavements exert a radiative forcing, meaning that they change the Earth’s energy balance by sending more energy out of the atmosphere — similar to the polar ice caps.”

    Cool pavements also exert complex, indirect climate change impacts by altering energy use in adjacent buildings.

    “On the one hand, by lowering temperatures, cool pavements can reduce some need for AC [air conditioning] in the summer while increasing heating demand in the winter,” says AzariJafari. “Conversely, by reflecting light — called incident radiation — onto nearby buildings, cool pavements can warm structures up, which can increase AC usage in the summer and lower heating demand in the winter.”

    What’s more, albedo effects are only a portion of the overall life cycle impacts of a cool pavement. In fact, impacts from construction and materials extraction (referred to together as embodied impacts) and the use of the pavement both dominate the life cycle. The primary use phase impact of a pavement — apart from albedo effects  — is excess fuel consumption: Pavements with smooth surfaces and stiff structures cause less excess fuel consumption in the vehicles that drive on them.

    Assessing the climate-change impacts of cool pavements, then, is an intricate process — one involving many trade-offs. In their study, the researchers sought to analyze and measure them.

    A full reflection

    To determine the ideal implementation of cool pavements in Boston and Phoenix, researchers investigated the life cycle impacts of shifting from conventional asphalt pavements to three cool pavement options: reflective asphalt, concrete, and reflective concrete.

    To do this, they used coupled physical simulations to model buildings in thousands of hypothetical neighborhoods. Using this data, they then trained a neural network model to predict impacts based on building and neighborhood characteristics. With this tool in place, it was possible to estimate the impact of cool pavements for each of the thousands of roads and hundreds of thousands of buildings in Boston and Phoenix.

    In addition to albedo effects, they also looked at the embodied impacts for all pavement types and the effect of pavement type on vehicle excess fuel consumption due to surface qualities, stiffness, and deterioration rate.

    After assessing the life cycle impacts of each cool pavement type, the researchers calculated which material — conventional asphalt, reflective asphalt, concrete, and reflective concrete — benefited each neighborhood most. They found that while cool pavements were advantageous in Boston and Phoenix overall, the ideal materials varied greatly within and between both cities.

    “One benefit that was universal across neighborhood type and paving material, was the impact of radiative forcing,” notes AzariJafari. “This was particularly the case in areas with shorter, less-dense buildings, where the effect was most pronounced.”

    Unlike radiative forcing, however, changes to building energy demand differed by location. In Boston, cool pavements reduced energy demand as often as they increased it across all neighborhoods. In Phoenix, cool pavements had a negative impact on energy demand in most census tracts due to incident radiation. When factoring in radiative forcing, though, cool pavements ultimately had a net benefit.

    Only after considering embodied emissions and impacts on fuel consumption did the ideal pavement type manifest for each neighborhood. Once factoring in uncertainty over the life cycle, researchers found that reflective concrete pavements had the best results, proving optimal in 53 percent and 73 percent of the neighborhoods in Boston and Phoenix, respectively.

    Once again, uncertainties and variations were identified. In Boston, replacing conventional asphalt pavements with a cool option was always preferred, while in Phoenix concrete pavements — reflective or not — had better outcomes due to rigidity at high temperatures that minimized vehicle fuel consumption. And despite the dominance of concrete in Phoenix, in 17 percent of its neighborhoods all reflective paving options proved more or less as effective, while in 1 percent of cases, conventional pavements were actually superior.

    “Though the climate change impacts we studied have proven numerous and often at odds with each other, our conclusions are unambiguous: Cool pavements could offer immense climate change mitigation benefits for both cities,” says Kirchain.

    The improvements to air temperatures would be noticeable: the team found that cool pavements would lower peak summer air temperatures in Boston by 1.7 C (3 F) and in Phoenix by 2.1 C (3.7 F). The carbon dioxide emissions reductions would likewise be impressive. Boston would decrease its carbon dioxide emissions by as much as 3 percent over 50 years while reductions in Phoenix would reach 6 percent over the same period.

    This analysis is one of the most comprehensive studies of cool pavements to date — but there’s more to investigate. Just as with pavements, it’s also possible to adjust building albedo, which may result in changes to building energy demand. Intensive grid decarbonization and the introduction of low-carbon concrete mixtures may also alter the emissions generated by cool pavements.

    There’s still lots of ground to cover for the CSHub team. But by studying cool pavements, they’ve elevated a brilliant climate change solution and opened avenues for further research and future mitigation.

    The MIT Concrete Sustainability Hub is a team of researchers from several departments across MIT working on concrete and infrastructure science, engineering, and economics. Its research is supported by the Portland Cement Association and the Ready Mixed Concrete Research and Education Foundation. More

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    Finding common ground in Malden

    When disparate groups convene around a common goal, exciting things can happen.

    That is the inspiring story unfolding in Malden, Massachusetts, a city of about 60,000 — nearly half people of color — where a new type of community coalition continues to gain momentum on its plan to build a climate-resilient waterfront park along its river. The Malden River Works (MRW) project, recipient of the inaugural Leventhal City Prize, is seeking to connect to a contiguous greenway network where neighboring cities already have visitors coming to their parks and enjoying recreational boating. More important, the MRW is changing the model for how cities address civic growth, community engagement, equitable climate resilience, and environmental justice.                                                                                        

    The MRW’s steering committee consists of eight resident leaders of color, a resident environmental advocate, and three city representatives. One of the committee’s primary responsibilities is providing direction to the MRW’s project team, which includes urban designers, watershed and climate resilience planners, and a community outreach specialist. MIT’s Kathleen Vandiver, director of the Community Outreach Education and Engagement Core at MIT’s Center for Environmental Health Sciences (CEHS), and Marie Law Adams MArch ’06, a lecturer in the School of Architecture and Planning’s Department of Urban Studies and Planning (DUSP), serve on the project team.

    “This governance structure is somewhat unusual,” says Adams. “More typical is having city government as the primary decision-maker. It is important that one of the first things our team did was build a steering committee that is the decision maker on this project.”

    Evan Spetrini ’18 is the senior planner and policy manager for the Malden Redevelopment Authority and sits on both the steering committee and project team. He says placing the decision-making power with the steering committee and building it to be representative of marginalized communities was intentional. 

    “Changing that paradigm of power and decision-making in planning processes was the way we approached social resilience,” says Spetrini. “We have always intended this project to be a model for future planning projects in Malden.”

    This model ushers in a new history chapter for a city founded in 1640.

    Located about six miles north of Boston, Malden was home to mills and factories that used the Malden River for power, and a site for industrial waste over the last two centuries. Decades after the city’s industrial decline, there is little to no public access to the river. Many residents were not even aware there was a river in their city. Before the project was under way, Vandiver initiated a collaborative effort to evaluate the quality of the river’s water. Working with the Mystic River Watershed Association, Gradient Corporation, and CEHS, water samples were tested and a risk analysis conducted.

    “Having the study done made it clear the public could safely enjoy boating on the water,” says Vandiver. “It was a breakthrough that allowed people to see the river as an amenity.”

    A team effort

    Marcia Manong had never seen the river, but the Malden resident was persuaded to join the steering committee with the promise the project would be inclusive and of value to the community. Manong has been involved with civic engagement most of her life in the United States and for 20 years in South Africa.

    “It wasn’t going to be a marginalized, token-ized engagement,” says Manong. “It was clear to me that they were looking for people that would actually be sitting at the table.”

    Manong agreed to recruit additional people of color to join the team. From the beginning, she says, language was a huge barrier, given that nearly half of Malden’s residents do not speak English at home. Finding the translation efforts at their public events to be inadequate, the steering committee directed more funds to be made available for translation in several languages when public meetings began being held over Zoom this past year.

    “It’s unusual for most cities to spend this money, but our population is so diverse that we require it,” says Manong. “We have to do it. If the steering committee wasn’t raising this issue with the rest of the team, perhaps this would be overlooked.”

    Another alteration the steering committee has made is how the project engages with the community. While public attendance at meetings had been successful before the pandemic, Manong says they are “constantly working” to reach new people. One method has been to request invitations to attend the virtual meetings of other organizations to keep them apprised of the project.

    “We’ve said that people feel most comfortable when they’re in their own surroundings, so why not go where the people are instead of trying to get them to where we are,” says Manong.

    Buoyed by the $100,000 grant from MIT’s Norman B. Leventhal Center for Advanced Urbanism (LCAU) in 2019, the project team worked with Malden’s Department of Public Works, which is located along the river, to redesign its site and buildings and to study how to create a flood-resistant public open space as well as an elevated greenway path, connecting with other neighboring cities’ paths. The park’s plans also call for 75 new trees to reduce urban heat island effect, open lawn for gathering, and a dock for boating on the river.

    “The storm water infrastructure in these cities is old and isn’t going to be able to keep up with increased precipitation,” says Adams. “We’re looking for ways to store as much water as possible on the DPW site so we can hold it and release it more gradually into the river to avoid flooding.”

    The project along the 2.3-mile-long river continues to receive attention. Recently, the city of Malden was awarded a 2021 Accelerating Climate Resilience Grant of more than $50,000 from the state’s Metropolitan Area Planning Council and the Barr Foundation to support the project. Last fall, the project was awarded a $150,015 Municipal Vulnerability Preparedness Action Grant. Both awards are being directed to fund engineering work to refine the project’s design.

    “We — and in general, the planning profession — are striving to create more community empowerment in decision-making as to what happens to their community,” says Spetrini. “Putting the power in the community ensures that it’s actually responding to the needs of the community.”

    Contagious enthusiasm

    Manong says she’s happy she got involved with the project and believes the new governance structure is making a difference.

    “This project is definitely engaging with communities of color in a manner that is transformative and that is looking to build a long-lasting power dynamic built on trust,” she says. “It’s a new energized civic engagement and we’re making that happen. It’s very exciting.”

    Spetrini finds the challenge of creating an open space that’s publicly accessible and alongside an active work site professionally compelling.

    “There is a way to preserve the industrial employment base while also giving the public greater access to this natural resource,” he says. “It has real implications for other communities to follow this type of model.”

    Despite the pandemic this past year, enthusiasm for the project is palpable. For Spetrini, a Malden resident, it’s building “the first significant piece of what has been envisioned as the Malden River Greenway.” Adams sees the total project as a way to build social resilience as well as garnering community interest in climate resilience. For Vandiver, it’s the implications for improved community access.

    “From a health standpoint, everybody has learned from Covid-19 that the health aspects of walking in nature are really restorative,” says Vandiver. “Creating greater green space gives more attention to health issues. These are seemingly small side benefits, but they’re huge for mental health benefits.”

    Leventhal City Prize’s next cycle

    The Leventhal City Prize was established by the LCAU to catalyze innovative, interdisciplinary urban design, and planning approaches worldwide to improve both the environment and the quality of life for residents. Support for the LCAU was provided by the Muriel and Norman B. Leventhal Family Foundation and the Sherry and Alan Leventhal Family Foundation.

    “We’re thrilled with inaugural recipients of the award and the extensive work they’ve undertaken that is being held up as an exemplary model for others to learn from,” says Sarah Williams, LCAU director and a professor in DUSP. “Their work reflects the prize’s intent. We look forward to catalyzing these types of collaborative partnership in the next prize cycle.”

    Submissions for the next cycle of the Leventhal City Prize will open in early 2022.    More