Critical Review

The 48th Annual A&WMA Critical Review

Trends in Onroad Transportation Energy and Emissions 

Tuesday, June 26, 9:00 am – 11:45 am

H. Christopher Frey  (bio
Distinguished University Professor, North Carolina State University 
Over the last hundred years, the automobile was responsible for major social and economic trends in land use, housing, commuting, and personal mobility. The number of registered onroad vehicles in the United States grew from 8,000 in 1900 to an estimated 268 million as of 2015.
Increases in vehicle fuel economy have helped offset growth in vehicle energy use despite the growth in the size of the vehicle fleet and VMT. Mitigation of growth in fuel consumption via more efficient vehicles also helps mitigate growth in emissions. In 1970, the fuel economy for an average light-duty vehicle in the United States was 13.5 miles per gallon (mpg). By 2000, light-duty vehicles averaged 21.9 mpg.
Growing recognition of their impact on the environment resulted in the inclusion of the first national vehicle emissions standards in the 1970 U.S. Clean Air Act. U.S. vehicle emissions of CO, NOx, VOCs, and particulate matter have declined steadily in the last two decades despite continued growth in VMT. Today, the United States is one of the most motorized nations, at 821 vehicles per 1,000 people in 2015, and continues to have more vehicles than any other country.
The 48th Annual A&WMA Critical Review focuses on answering the following key technical and policy questions regarding trends in onroad transportation energy and emissions: 
  • What are the historic trends in onroad vehicle technology, fuel efficiency, and emissions?
  • How effective are onroad fleet fuel economy and vehicle emissions standards?
  • What are the current trends in onroad vehicle technology and operation that affect energy use and emissions?
  • Are real-world onroad fuel economy and emissions consistent with fuel economy and emissions regulations, respectively?
  • What are the emerging challenges and opportunities related to onroad vehicle energy consumption and emissions?
  • What are the advances in measurement and monitoring of onroad vehicle energy consumption and emissions, and what new capabilities do these advances enable?
  • What are the impacts of onroad transportation on public health and the environment?
  • How can exposure to onroad transportation-related air pollution be managed? 
Since the United States has long had the world’s largest vehicle fleet, these questions are answered mostly in the context of the U.S. situation. However, different fleet mix, regulatory programs, and rates of motorization enable comparative assessments based on an international perspective. Therefore, the Review addresses key lessons from other parts of the world, particularly from Europe and China. Transportation includes highway vehicles, nonroad vehicles (e.g., construction, farm, and industrial equipment, lawn and garden equipment, recreational vehicles), rail, pipelines, waterborne vessels, and aviation. The focus of this Review is on highway vehicles.

Invited Discussants
Following the presentation, a panel of invited experts will critique the presentation and offer their perpsectives on current topics in vehicle emissions. This year’s invited discussants are:
Alberto Ayala, Executive Director, Sacramento Metropolitan Air Quality Management District
Susan Collet, Senior Principal Engineer, Toyota Motor Engineering and Manufacturing North America
Rashid Shaikh, Director of Science , Health Effects Institute
Eric Stevenson, Director of Meteorology, Measurement and Rules, Bay Area Air Quality Management District
Michael P. Walsh, Independent Consultant, International Council on Clean Transportation

Comments also will be solicited from the floor and from written submissions to the Critical Review Committee Chair.