Full Content is available to subscribers

Subscribe/Learn More  >

Meeting the Challenge: A Stochastic Assessment of the U.S. Light-Duty Vehicle Fuel Economy Standards

[+] Author Affiliations
Parisa Bastani

University of Cambridge, Cambridge, UKMIT, Cambridge, MA

John B. Heywood

Massachusetts Institute of Technology, Cambridge, MA

Chris Hope

University of Cambridge, Cambridge, UK

Paper No. ES2012-91172, pp. 1145-1154; 10 pages
  • ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology
  • ASME 2012 6th International Conference on Energy Sustainability, Parts A and B
  • San Diego, California, USA, July 23–26, 2012
  • Conference Sponsors: Advanced Energy Systems Division, Solar Energy Division
  • ISBN: 978-0-7918-4481-6
  • Copyright © 2012 by ASME


The U.S. Department of Transport and EPA have recently proposed further regulation of the light-duty vehicle corporate average fuel economy and GHG emissions for model years 2017 to 2025. Policy makers are setting more stringent targets out to 2025 in a context of significant uncertainty. These uncertainties need to be quantified and taken into account systematically when evaluating policies. In this paper, a stochastic technology and market vehicle fleet analysis is carried out, using the STEP (Stochastic Transport Emissions Policy model), to assess the probability of meeting the proposed CAFE targets in 2016 and 2025, and identify factors that play key roles in the near and midterm. Our results indicate that meeting the proposed targets requires (a) aggressive technological progress rate and deployment, (b)aggressive market penetration of advanced engines and powertrains, (c) aggressive vehicle downsizing and weight reduction, and (d) a high emphasis on reducing fuel consumption. Three scenarios are examined to assess the likelihood of meeting the proposed targets. The targets examined here, 32.5 and 34.1 mpg in 2016 and 44 and 54.5 mpg in 2025, are reduced from the nominal CAFE values after allowing for the various credits in the proposed rulemaking. The results show that there is about a 42.5% likelihood of the passenger cars average fuel economy falling below 32.5 mpg and a 5.3% likelihood of it exceeding 34.1 mpg in 2016, and about a 4% chance of it exceeding 44 mpg in 2025, under the plausible-ambitious scenario. Under the EPA/DOT preferred alternative scenario, the likelihood of passenger cars average fuel economy meeting or exceeding 34.1 mpg in 2016 and 44 mpg in 2025 increases to about 74% and 34.5% respectively. The probability of meeting these combined CAFE targets drops to less than 1% in both near and mid terms, once light trucks are included in the mix. This analysis quantifies the probability of meeting the targets therefore to enable risk-based contingency planning, and identifies key drivers of uncertainty where further strategic research is needed.

Copyright © 2012 by ASME



Interactive Graphics


Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In