Small, lightweight vehicles are more vulnerable in collisions with larger, heavier cars and trucks, and the safety agency says it is taking that into account in structuring its fuel-economy requirements.
Honda Accord among models in NHTSA’s crash simulations.
DETROIT – Results from an ongoing study on the effects of lightweighting on vehicle safety will be among factors considered by the National Highway Traffic Safety Admin. in its midterm review of federal fuel-economy standards, an official from the agency says at the 2013 SAE World Congress here.
Speaking on a panel to discuss the industry movement to cut vehicle mass, James Tamm, chief-Fuel Economy Div., says NHTSA so far is confident measures taken to increase U.S. fleet fuel economy to 35.5 mpg (6.6 L/100 km) in 2016 and to 54.5 mpg (4.3 L/100 km) in 2025 won’t jeopardize safety.
Cutting weight will remain a primary focus as auto makers look to meet higher corporate average fuel economy standards set by NHTSA and carbon-dioxide limits established by the Environmental Protection Agency, experts here say.
Tamm points to an industry adage that for every 10% cut in mass, there’s a 6.5% improvement in fuel economy, assuming the vehicle’s engine also is downsized. “So mass reduction will continue to be a key technology moving forward,” he says.
But lighter also can often mean smaller, and small, lightweight vehicles are more vulnerable in collisions with larger, heavier cars and trucks, safety advocates have noted.
Tamm says NHTSA eliminated size as a “social-safety” concern when it based CAFE standards on vehicle footprint (the area between their four wheels on the ground). NHTSA’s social-safety analysis goes beyond the basic crashworthiness of an individual vehicle and examines the safety impact of lighter vehicles as they enter the U.S. fleet and interact with older vehicles already on the road.
“Making vehicles smaller can have adverse social-safety effects,” Tamm admits. “But with the footprint-based CAFE, there’s no incentive for the manufacturer to make a vehicle smaller or larger,” so the relative size of the U.S. fleet should remain about where it is today.
Cutting weight is another issue. NHTSA says accident data over several decades indicates mass reduction doesn’t pose a significant risk to safety, but the agency is conducting crash simulations using advanced-technology vehicles to determine if that will be true in the future as well.
The simulations use standard models now on the road, such as a currentAccord and Taurus, plus lightweight versions of the Accord and Venza in various vehicle-to-vehicle and vehicle-to-object crashes at speeds of 15-40 mph (24-64 km/h).
NHTSA still is finalizing its report, and Tamm won’t hint at early indications from the study. But he does say findings could lead to changes in how vehicle airbag deployment is timed or in the adoption of adaptive-seatbelt technology.
The report is expected later this year. As part of its midterm CAFE review, NHTSA must complete a technical report by Nov. 15, 2017, and the EPA must either adjust or confirm its CO2-related mileage targets for 2022-2025 by April 1, 2018.
“That (crash study), plus a lot of other factors, will play a role in the midterm review,” Tamm tells WardsAuto.
Whatever the result of NHTSA’s modeling, auto makers already are working to ensure basic vehicle safety doesn’t deteriorate as mass is reduced.
“No doubt in my mind, safety will not be compromised,” says Jay Baron, president and CEO of the Ann Arbor, MI-based Center for Automotive Research and a member of the panel here.