The National Academies, a top government research group tasked with determining the impact and effectiveness of fuel-economy laws in the U.S., says it needs more information on the cost to auto makers of alternative-propulsion technologies in order to complete its report.

In a letter to the National Highway Traffic Safety Admin. that contains a preliminary assessment of the alternative technologies it will study for a final report on corporate average fuel economy, the National Academies characterizes its current data on potential costs as “insufficient.”

The organization recently was tasked by NHTSA to update its 2001 report on fuel-economy rules, “Effectiveness and Impact of Corporate Average Fuel Economy Standards,” and add an assessment of technologies that have emerged since the paper was prepared. NHTSA directed the National Academies to estimate the efficacy, cost, and applicability of technologies auto makers might add to cars and light trucks over the next 15 years.

The list provided in the preliminary findings and scheduled for further investigation includes diesel and hybrid-electric powertrains, which the National Academies did not address in 2001. It will include weight and power reductions, as well, although it will not examine NHTSA’s structure of fuel-economy standards.

Information on the potential cost of alternative powertrains, which some auto makers estimate adds as much as $10,000 to the price of a vehicle, would be important to NHTSA and the Environmental Protection Agency as they begin implementation of the new CAFE standard and regulate greenhouse-gas emissions.

But in a letter to NHTSA Administrator Nicole Nason, Trevor Jones, the National Academies fuel-economy research group chairman, says additional information is needed from NHTSA on the cost of alternative-propulsion technologies.

“The information provided to (us) by automobile manufacturers and technology suppliers was insufficient,” Jones writes.

According to Jones, the National Academies planned to supplement that information with fuel economy rule data due at the end of last year from NHTSA and the EPA. But last year’s passage of a controversial new CAFE standard, which calls for the U.S. fleet of cars and trucks to achieve an average 35 mpg (6.7 L/100 km) by 2020, delayed the data.

Sara Frueh, spokeswoman for the National Academies, tells Ward’s her group expects cost data gathered by NHTSA – during what the National Academies calls “extensive discussions” with auto makers and suppliers – will arrive soon. The organization will publish its final analysis this spring.

During the interim, the National Academies says it also intends to select one partial-discrete-approximation (PDA) model and one fuel-system-simulation (FSS) model to use in its analysis of the fuel-economy effects of alternative propulsion.

An “inside-out approach,” the FSS model would examine interactions between vehicle components and provide information about applying a combination of technologies to a vehicle; the effects such an application might have on vehicle performance; and whether any fuel-economy benefit would be realized.

However, the group says, proprietary information from auto makers will be needed to complete the FSS model.

The National Academies considers the PDA model an “outside-in approach,” where it gathers data from a number of sources, such as vehicle certifications, on a wide range of proven technologies already in use on a mass-produced vehicle.

The group says the approach offers the potential to estimate the effects of fuel-economy technologies in a broad array of vehicle types. It also can perform the assessment for an entire vehicle class without simulating every model within that class.

The National Academies also notes in its letter that it does not expect commercialization of hydrogen fuel-cell vehicles or all-electric vehicles before 2020. As a result, it will not include those technologies in its final assessment.

jamend@wardsauto.com