Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety

The document examines the relationship between vehicle weight, fuel efficiency, and safety. It argues that lightweighting can significantly reduce global greenhouse gas emissions—potentially by up to 11% if combined with plug-in hybrid electric vehicles (PHEVs) and a clean grid—without compromising occupant safety. The author contends that vehicle size and design, rather than mass, are the primary drivers of crashworthiness. The paper reviews statistical literature to debunk the 'weight confers safety' argument and provides examples of aluminum, high-strength steel, and carbon fiber composites being used in safe, lightweight vehicles.

• Lightweighting vehicles significantly improves fuel economy and reduces emissions; a 10% reduction in weight generally leads to a 7% increase in fuel economy.
• Aggressive lightweighting combined with plug-in hybrid electric vehicles (PHEVs) and a California-type electricity grid could lead to an approximately 11% reduction in global greenhouse-gas emissions.
• Research indicates that vehicle size (wheelbase and track length) and design (crash-absorbing structures and center of gravity) are the primary factors in crashworthiness, whereas weight is more strongly correlated with 'aggressivity' (the likelihood of killing others in a crash).
• Analysis by Dynamic Research, Inc. (DRI) found that reducing passenger vehicle fleet weight while maintaining wheelbase and track constant could actually reduce the number of traffic fatalities.
• Lightweight materials such as aluminum, high-strength steels, and carbon fiber reinforced plastics (CFRPs) can meet or exceed the safety performance of traditional mild steel when properly designed.
• Active safety features, such as electronic stability control (ESC), which the NHTSA predicts could save between 5,300 and 9,600 lives annually, provide safety improvements that are independent of vehicle weight.

APA

Schewel, L. (2008). Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety. RMI. https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_SAE_TripleSafetyPaper_2008-01-1282_LS.pdf

Chicago

Schewel, Laura. Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety. RMI, 2008. https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_SAE_TripleSafetyPaper_2008-01-1282_LS.pdf.

Wikipedia

{{cite report |last1=Schewel |first1=Laura |title=Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety |publisher=RMI |date=2008 |url=https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_SAE_TripleSafetyPaper_2008-01-1282_LS.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{schewel2008triple, author = {Schewel, Laura}, title = {{Triple Safety: Lightweighting Automobiles to Improve Occupant, Highway, and Global Safety}}, institution = {RMI}, year = {2008}, url = {https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_SAE_TripleSafetyPaper_2008-01-1282_LS.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }