Maximizing Pavement Life with Innovative Decision-Making Framework
Roads are the lifelines of our society and economy, facilitating the movement of people and goods across vast distances. With nearly 2.8 million lane-miles (or 4.6 million lane-kilometers) of roads crisscrossing the United States, it’s clear that our infrastructure plays a crucial role in our daily lives. However, the environmental impact of these roads cannot be ignored, with over 75 megatons of greenhouse gases (GHG) being emitted annually in the U.S. over the past three decades. This is equivalent to the emissions of a gasoline-powered passenger vehicle traveling over 190 billion miles each year, or circling the Earth more than 7.5 million times.
As we look to the future, it is estimated that emissions from the pavement sector will decrease by 14% by 2050, thanks to advancements like cement clinker replacement. However, there is potential for even greater reductions – up to 65% – by investing in materials and maintenance practices that make road networks stiffer and smoother. This not only improves driving conditions but also reduces the energy required to traverse these roads. For instance, in 2022, vehicles in the U.S. collectively traveled 3.2 trillion miles. If we were to improve the average surface roughness of all pavements by just 1%, we could save a staggering 190 million tons of CO2 emissions annually.
However, one of the major challenges hindering greater GHG reductions is data scarcity. Decision-makers often struggle to evaluate the environmental impact of roads across their entire life cycle, from production to construction, use, maintenance, and eventual demolition. The lack of comprehensive data and the complexity of calculations make it difficult to make informed decisions on materials and maintenance practices. In a rapidly changing world with shifting weather patterns and traffic flows, it’s crucial to have a clear understanding of the environmental impact of our infrastructure.
To address these challenges, the Concrete Sustainability Hub (CSHub) at MIT has developed an innovative decision-making framework that aims to maximize pavement life while minimizing environmental impact. By controlling uncertainties and prioritizing key data points, this framework streamlines the life-cycle assessment (LCA) process, making it more accessible and practical for stakeholders involved in pavement projects.
Streamlining Life-Cycle Assessments
Traditionally, conducting pavement LCAs has been a costly and labor-intensive process. Many assessments simplify the calculations by using fixed input values or focusing solely on upfront emissions from materials production and construction. However, this approach fails to account for uncertainties and variations, leading to potentially unreliable results. The CSHub’s novel framework aims to embrace and control these uncertainties, enabling decision-makers to make robust and informed choices.
Haoran Li, a postdoc at CSHub and lead author of the study, emphasizes the importance of understanding the minimum amount of data required to achieve a reliable decision. By keeping uncertainties in check and prioritizing key data points, the streamlined LCA framework reduces the overall data collection burden by up to 85%, without compromising the accuracy of the conclusions drawn.
Data Specificity and Environmental Impact
To illustrate the effectiveness of their framework, the MIT researchers modeled the life-cycle environmental impacts of a pavement in Boston. The team compared two different pavement designs – an asphalt pavement and a jointed plain concrete pavement – over a 50-year life expectancy. By varying the level of data specificity from M1 to M4, they were able to assess how different data inputs influenced the range of life-cycle assessment results for each design.
Regardless of the level of data specificity, the researchers found that certain components of the life cycle remained consistent in their contribution to GHG emissions. For concrete pavements, embodied emissions from construction and maintenance accounted for about half of the total emissions, while for asphalt pavements, usage-phase emissions dominated, comprising between 70-90% of the pavement’s life-cycle emissions.
The results from the Boston case study showed that combining an M2 level of data specification with an M3 knowledge of maintenance and rehabilitation led to a decision-making process with 90% reliability. This indicates that with the right balance of data specificity and understanding of maintenance strategies, stakeholders can make informed choices that prioritize environmental sustainability.
Democratizing Pavement LCA
To make this streamlined framework more accessible to stakeholders, the MIT researchers are working on integrating the approach into an online life-cycle assessment tool. This tool aims to democratize pavement LCA, empowering departments of transportation, metropolitan planning organizations, and other key players in the value chain to identify pavement choices that are not only high-performing and long-lasting but also environmentally friendly.
By providing a structured data underspecification framework, the CSHub team is revolutionizing the way we approach pavement life-cycle assessments. By prioritizing key data points and controlling uncertainties, decision-makers can make informed choices that maximize pavement life while minimizing environmental impact. As we look to the future of our infrastructure, innovations like these will play a crucial role in building a more sustainable and resilient society.