The world is transforming its energy system from one dominated by fossil fuel combustion to one with net-zero emissions of carbon dioxide. Research overwhelmingly shows that this energy transition is critical to mitigating climate change, protecting human health, and revitalizing the economy.
Achieving net-zero carbon emissions in the United States by 2050 is feasible and would not only help address climate change but also build a more competitive economy, increase high-quality jobs, and help address social injustice in the energy system, according to
Accelerating Decarbonization of the U.S. Energy System from the National Academies of Sciences, Engineering, and Medicine.
One of the most significant actions recommended to accomplish this goal is ensuring zero emissions vehicles reach approximately 50% of new vehicle sales across all classes (light, medium, and heavy) by 2030 according to the report. Another step is to build the critical infrastructure needed, including a national CO2 transportation network to move captured CO2 to geologic reservoirs and an expanded network of electric vehicle charging stations.
Chris Hendrickson, NAE member and professor emeritus of civil and environmental engineering at Carnegie Mellon University, discusses in
TRB’s Transportation Explorers podcast how transportation, still dependent on petroleum, is now the single-largest sector for U.S. greenhouse gas emissions (GHG). Hendrickson served on the National Academies and spoke with TRB about how we can get to net-zero carbon emissions in the foreseeable future.
Evaluating Emissions
With changes to electric vehicle prevalence on the horizon, another new National Academies report addresses the potential for internal combustion engine, hybrid, battery electric, fuel cell, nonpowertrain, and connected and automated light-duty vehicle (LDV) technologies to contribute to efficiency in the more immediate future.
Assessment of Technologies for Improving Light-Duty Vehicle Fuel Economy—2025-2035 notes that zero-emission vehicles (ZEVs) represent the long-term future of energy efficiency, petroleum reduction, and GHG emissions reduction in the LDV fleet, and recommends that the National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) use all their delegated authority to drive development and deployment of ZEVs. Given their expected growth in the market, the report highlights the importance of considering ZEVs in the setting of the corporate average fuel efficiency (CAFE) standard stringency, which currently does not consider the efficiency of such vehicles. The report recommends that Congress recognize the importance of GHG emissions in the goals of CAFE program alongside other goals of energy security and fuel efficiency.
As types of fuel used in LDVs move beyond primarily gasoline and diesel, the report recommends that Congress, NHTSA, and EPA should consider updating long-term energy and emissions policy and standards to include the full vehicle and fuel lifecycle emissions and energy consumption. The agencies should assess when it makes sense to implement a full-fuel-cycle approach. This means considering the consequences of the current temporary exclusion of upstream emissions for ZEVs and using those results to determine an approach for accounting upstream ZEV emissions for compliance.
Fuel economy standards need updating to accommodate not just for ZEVs, but also efficiency benefits of other vehicle technologies, including connected and automated vehicle (CAV) technologies. To better understand the on-road efficiency and emissions reduction benefits of all technologies, the two agencies should implement a program that measures fuel consumption and GHG emissions from the LDV fleet in use. They should also study current driving patterns and new vehicle technology impacts and examine how well they are reflected by current vehicle certification test cycles. CAV technologies are an example where efficiency benefits may not be captured on the current test cycles, so their benefits would need to be carefully documented if they are to receive off-cycle credits for efficiency performance.
Get on the zero emissions bus
The zero‐emission bus (ZEB) market, including Battery Electric Buses and Fuel Cell Electric Buses is already on its way. As noted in recent TRB Transit Cooperative Research Program (TCRP) research on best practices and lessons learned in ZEB deployments,
Guidebook for Deploying Zero-Emission Transit Buses, ZEBs have seen significant growth in recent years.
They can be powered by fully renewable sources and have zero harmful tailpipe emissions. As the market share of ZEBs continues to grow, the price of producing these environmentally friendly vehicles has been decreasing and they’re rolling through cities across the world. As they increase in popularity, Latin American officials can now use a new
contractual model, detailed in a paper published in
Transportation Research Record (TRR), which can be used to lower emissions and transit costs while improving the quality of service.
California’s governor recently issued an executive order stating that all in-state sales of new passenger cars and trucks will be
zero-emission by 2035 and medium- and heavy-duty trucks by 2045.
An
active TRB Transit Innovations Deserving Exploratory Analysis (IDEA) project is evaluating a decision support tool designed to give greater insight into which routes ZEBs can serve most effectively, the locations where charging facilities would be most useful, and the right size onboard battery depending on a specific route. Transit agencies will be looking for cost-efficiency, service continuity, and environmental friendliness in using these tools to electrify their bus fleets. The Transit IDEA Oversight panel heard from the
Canadian Urban Transit Research & Innovation Consortium’s Zero Emission Bus Simulation & Commercialization key innovation priorities.
Lessening emissions in the supply chain
Zero-emissions trucks have made news as
California adopts the Advanced Clean Truck regulation, requiring manufacturers to begin selling zero-emission models as soon as 2024. Fifteen states (including California) and D.C. have also signed a joint memorandum of understanding to
advance the market for electric medium- and heavy-duty trucks. The collective goal is to ensure all trucks sold in these two categories are ZEVs by 2050.
Demand for more and faster home deliveries, especially in light of the coronavirus (COVID-19) pandemic, means more vehicles are needed. The TRB National Cooperative Highway Research Program’s (NCHRP)
Guide to Truck Activity Data for Emissions Modeling explores methods, procedures, and datasets needed in estimating and forecasting criteria pollutants, air toxins, and greenhouse gas emissions from goods and services movement.
To better understand how commercial vehicles affect the environment in California, the state began a
Vehicle Inventory and Use Survey, as published in TRR, to gain insights on commercial vehicle movements on air quality along with economic activity, safety, and usage.
Larger vehicles aren’t only on the roads to deliver products; they also provide services. Utility service trucks, like those that fix power lines, often sit at a job site for many hours. Hybrid systems, as noted in the National Academies’
Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two can take advantage of battery power during the times the trucks are not being driving to allow workers to power the other functions of the truck, like buckets that raise and lower them to the service.
A 2014 report from TRB’s National Cooperative Freight Research Program,
Sustainability Strategies Addressing Supply-Chain Air Emissions, identifies potential strategies for accelerating environmental improvement, enhancing performance, and promoting social responsibility of supply chains as a whole. To do so, it explored the impact of environmental policies and regulations, focusing specifically on GHG emissions in the interrelationships between economic drivers and air quality.
Finding the right conditions to increase personal ownership
Hybrid and electric passenger cars and trucks make up about 3% of personal vehicle sales. Over the next 20 years, the number of passenger vehicles and trucks that are not internal combustion engine vehicles are expected to increase to 15% of the U.S. vehicle population.
General Motors, for one, announced it will stop making gasoline powered light duty vehicles by 2035.
For now, car and gas prices seem to be the biggest factors in preventing people from owning an electric vehicle.
Forecasting Zero-Emissions Vehicles (ZEV) Fleet Scenarios and Emissions Implications, from NCHRP, reports that emissions models for 2040 show that if the purchase price of a new zero-emission vehicle is equal to conventional vehicles by 2030
and if gas prices increase at an accelerated rate over the next 30 years, there will be significant reductions in tailpipe emissions.
In 2020,
TRB hosted a webinar that further explained the research methods used in the report. Policymakers at state departments of transportation, metropolitan planning organizations, and elsewhere can play an important role in increasing the number of ZEVs into light-duty vehicle fleets.
Lowering vehicle emissions beyond the roads
Forthcoming ACRP research will help the airport industry account for
electric aircraft operations in their planning.
Commuter rail may also be able to reduce wasted thermal energy. A Transit IDEA project,
Diesel-Electric Locomotive Energy Recovery and Conversion tested retrofitting locomotives with electric generator technology to ultimately reduce pollutants.
Even cargo ships have a version of electrical vehicles. An
article in TR News explains “cold ironing,” the provision of electrical plug-in power for vessels when they’re in port. The article notes that international shipping was responsible for about 2.4% of global greenhouse gas emissions in 2018, and that number is expected to increase.
Be it on land, at sea, or in the air, research is proving that effective processes, practices, and technology can lessen greenhouse gas emissions from transportation.
Go greener with TRB
Transportation accounts for more than a quarter of U.S. greenhouse gas emissions–the largest share–and it is an issue the industry is addressing across the board, as highlighted in TRB’s
Critical Issues in Transportation 2019.
As technology, the market, and policy evolve, TRB will continue to focus on research in this field. Get involved with future Cooperative Research Program work. Look for
ongoing information on new projects, requests for proposals, or to nominate yourself or others to serve on a project panel. Submit problem statement research ideas and find new announcements in
TRB’s weekly newsletter or on the homepages for
ACRP,
NCHRP, and
TCRP.
Become a friend of any one of TRB’s standing committees working on environment and energy topics: the
Standing Committee on Transportation Energy, the
Standing Committee on Marine Environment, the
Standing Committee on Environmental Issues in Aviation, or the
Standing Committee on Environmental Issues in Transportation Law. Most relevant to zero-emissions vehicles is TRB’s
Standing Committee on Alternative Fuels and Technologies.
Transportation technologies and new approaches to mobility are advancing so rapidly that it can be difficult for policy makers to frame incentives, regulations, and market signals to promote all three pillars of sustainability: equity, the environment, and the economy. Join TRB in 2022 for the
Conference on Sustainability and Emerging Transportation Technology to help address these questions. Share your expertise and help move zero-emissions technology research into the future.
TRB and Cooperative Research Program reports cited in this article:
TRB standing technical committees cited in this article:
Articles published in TRR cited:
Articles published in TR News cited:
TRB events:
Active projects:
Additional TRB resources:
External articles cited in this report:
National Academies of Sciences, Engineering, and Medicine resources:
Contact:
Beth Ewoldsen, Content Strategist
Transportation Research Board
202-334-2353;
bewoldsen@nas.edu
Published September 30, 2020, most recently updated April 2021
This Summary Last Modified On: 4/1/2021