New TRECH Project Research Update on Health Benefits of TCI Policy Scenarios

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October 07, 2020

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(Harvard Center for Climate, Health and the Global Environment) Transportation is the largest source of greenhouse gas (GHG) emissions in the United States and in the Northeast and Mid-Atlantic regions at about 28% and 30%, respectively (EPA 2020, TCI 2010). Cars, trucks, and buses also emit tons of conventional air pollutants each year contributing to asthma, heart disease, pre-term births, and premature death among other health impacts. The largest air quality impacts occur in underserved and overburdened communities, near highways and transportation depots, and among Black people and other people of color, due to a long history of racist policies that have resulted in persistent elevated pollution exposure. Transportation systems also affect noise pollution; congestion and stress; opportunities for safe biking and walking; and access to jobs, healthcare, and education.

A group of Northeast and Mid-Atlantic states and the District of Columbia are participating in the Transportation Climate Initiative (TCI). They are expected to finalize a memorandum of understanding in Fall 2020 that aims to cut carbon dioxide (CO₂) emissions from the transportation sector. The TRECH Project team is making preliminary results available as state policymakers and stakeholders are considering how best to design a TCI climate mitigation program and achieve health gains.

The TRECH Project

The Transportation, Equity, Climate and Health (TRECH) Project is a multi-university research initiative conducting an independent analysis of TCI policy scenarios to address carbon pollution from the transportation sector. The project looks at changes in health outcomes from active mobility (e.g., biking and walking) and air quality using published, peer-reviewed models commonly employed in regulatory analysis. To-date, the TRECH Project team has estimated health outcomes for five illustrative TCI policy scenarios representing a range of emissions reduction caps and investment strategies.

The preliminary TRECH results are intended to foster dialogue and help inform program design by illustrating how climate mitigation policies in the transportation sector can influence health outcomes. The actual benefits of a TCI program will depend on state policy decisions including the ambition of a CO₂ emission reduction cap, the formulas for allocating program proceeds among and within states, and the potential adoption of supporting policies.

Insights from Preliminary Results

The estimated health benefits under the five TCI climate mitigation policy scenarios are substantial and are larger than estimated TCI program proceeds, for a subset of benefits examined.

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The TCI policy scenario with the largest estimated health benefits has the most ambitious emissions reduction cap and the largest share of investments dedicated to public transit and active mobility.

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Under all five policy scenarios, health benefits are estimated to occur in all counties across the region and are concentrated in more populated areas.

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All five policy scenarios modestly reduce inequities in air pollution exposure between racial/ethnic groups but, even with the reductions estimated under the TCI policy scenarios, people of color would still face higher overall air pollution exposures and more emission reductions would be needed to address pre-existing inequities.

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Nearly a four-fold difference in the estimated health benefits exists across the five TCI policy scenarios, underscoring that there is a wide range of possible health outcomes and that actual health benefits will depend on state actions (Table 1).

About the Illustrative TCI Policy Scenarios

Under the proposed TCI cap and invest program, fuel suppliers would be required to hold allowances for the carbon content of the fuel they supply. The allowances would be auctioned off and the proceeds from those auctions would be allocated to states to reinvest. The illustrative TCI policy scenarios assume that the proceeds are evenly allocated to the participating states based on vehicle miles traveled and population. Each scenario allocates a percent of the program proceeds to 25 different transportation strategies bundled into five categories. Of the total auction proceeds, 83-92% is assumed to be reinvested in transportation improvements. The remainder is allocated to the category “indirect/other”.

To-date, the TRECH Project team has analyzed five illustrative TCI policy scenarios compared to a no-TCI policy scenario in 2032. The policy scenarios represent three carbon dioxide (CO₂) emissions reduction caps and three investment and policy mixes defined by states participating in the TCI process.

The three investment and policy mixes for the illustrative TCI scenarios examined here represent an emphasis on public transit and active mobility (Scenario A), an emphasis on vehicle electrification and fuel-switching (Scenario C), and a blend between the two (Scenario B).

The three caps examined here represent a 20%, 22%, and 25% CO₂emissions reduction from on-road vehicles from 2022 levels by 2032. This equates to a 1%, 3%, and 6% reduction in emissions between a no-TCI reference scenario and the TCI policy scenarios in 2032. For this research update, Scenario B was modeled with all three caps. Scenarios A and C were modeled with the 25% CO₂ emissions reduction cap. Additional scenarios will be analyzed in phase 2 of the TRECH Project. For more details, see the reference and policy scenario assumptions and the TCI strategy investment tool.

A Few Caveats

The TCI policy scenarios examined here are illustrative, not predictive, and are for the purpose of informing program design. Actual health benefits will depend on state actions.
The scenarios assume that 83% to 92% of proceeds are reinvested in the transportation system.
The analysis focuses on on-road emissions and does not directly incorporate potential changes in emissions from the electrical grid. A basic screening analysis was conducted of potential grid effects.
The air quality analysis was conducted at a 12 kilometer by 12 kilometer scale, which is much smaller than a county but larger than a neighborhood. This is highly detailed for a regional analysis but is not intended for examining changes at a neighborhood scale.
The analysis does not include climate-related health benefits and potential transportation-related health benefits that could accrue from improving safety, noise pollution, traffic congestion, and access to jobs, healthcare, and education.

Download the complete Research Update

Download the Technical Appendix

Download the slide presentation

TRECH Project Team

Sarav Arunachalam, PhD, Institute for the Environment, University of North Carolina, Chapel Hill
Calvin Arter, PhD candidate, University of North Carolina at Chapel Hill
Alique Berberian, MPH, Columbia Center for Children’s Environmental Health
Laura Buckley, PhD student, Boston University School of Public Health
Jonathan Buonocore, ScD, Center for Climate, Health, and the Global Environment, Harvard T.H. Chan School of Public Health
Charles Chang, MA, Institute for the Environment, University of North Carolina at Chapel Hill
Kathy Fallon Lambert, MS, Center for Climate, Health, and the Global Environment, Harvard T.H. Chan School of Public Health
Patrick Kinney, ScD, Boston University School of Public Health
Jon Levy, ScD, Boston University School of Public Health
Frederica Perera, PhD, Columbia Center for Children’s Environmental Health
Matthew Raifman, PhD student, Boston University School of Public Health READ MORE