Sales-weighted fuel economy slips slightly in August Auto briefs: Autonomous guidelines, adaptable tires, hydrogen fuel

Following a marked improvement in July, the average fuel economy among vehicles sold in the United States dropped back slightly in August.

According to researchers at the University of Michigan Transportation Research Institute, the typical combined fuel economy for a vehicle sold during this month was 25.3 miles per gallon. This was down from 25.4 miles per gallon in the previous month, but up from 25.1 miles per gallon in August 2016.

UMTRI researchers Michael Sivak and Brandon Schoettle have been tracking fuel economy trends in U.S. vehicle purchases since October 2007, when the average vehicle got 20.1 miles per gallon. Sivak and Schoettle use monthly sales data as well as the window sticker values for combined city and highway mileage from the Environmental Protection Agency's "Fuel Economy Guide" to determine the typical fuel economy of cars, light trucks, SUVs, and vans sold each month.

The average sales-weighted fuel economy increased gradually from the start of the research, reaching a high of 25.5 miles per gallon in August 2014. The model year average, which takes into account fuel economy figures from October to September, climbed from 20.8 miles per gallon for the 2008 model year average to 25.1 miles per gallon for the 2014 model year average.

Improvements to sales-weighted fuel economy stalled in late 2014, when gasoline prices began to drop. The model year average remained unchanged in 2015 and 2016, and the average fuel economy in newly purchased vehicles wavered between 24.8 miles per gallon and 25.3 miles per gallon until the improvement in July. Sivak said the high average for that month was a result of light trucks making up a smaller share of the month's sales.

In addition to the fuel economy research, Sivak and Schoettle track changes to a figure called the Eco-Driving Index. This compares the estimated greenhouse gas emissions generated by new vehicle drivers to those of drivers in October 2007. The update is issued on a two-month delay due to a corresponding lag in data from the Federal Highway Administration.

The Eco-Driving Index for June stood at 0.83, indicating that emissions were down 17 percent from baseline levels. This was up from 0.82 in May and unchanged from June 2016. The lowest Eco-Driving Index, 0.78, was recorded in November 2013.

In June, the number of vehicle miles traveled in the U.S. was 3 percent higher than in October 2007. The estimated fuel used per distance driven was 19 percent lower than in that month.

New guidelines for the development of self-driving vehicles, tires designed to adapt to road conditions, and the opening of several new hydrogen fueling stations were among the items promoted by automakers and automotive entities recently.

• The Department of Transportation and National Highway Traffic Safety Administration recently updated the federal guidelines for automated vehicle technology. "Automated Driving Systems: A Vision for Safety 2.0" aligns the latest guidance with developments in self-driving vehicles as well as terminology in the field. The new policy focuses on Levels 3 to 5 of planned automation, including systems that can handle all driving tasks in some circumstances, but may still alert a human driver that they need to resume control; systems that can handle all driving tasks with no need for humans to resume control, but only in certain circumstances; and full automation where drivers never need to take control. The DOT and NHTSA says the policy is designed to be flexible to adjust to changing developments, and that guidelines for 3.0 are already in planning.

• The tire company Continental has introduced a pair of technologies designed to adapt to road conditions and better alert drivers of any problems. ContiAdapt uses micro-compressors in the wheel to change the tire pressure, thus adjusting the size of the rubber patch making contact with the road; for example, the tire can set a lower pressure and increase its contact patch for better handling on slippery surfaces. ContiSense uses sensors and electrically conductive rubber compounds to warn drivers if tread depth or temperature are above or below their limits; the sensors can also immediately send an alert if a puncture occurs. Both technologies debuted at the Frankfurt Motor Show in Germany.

• Two automakers are collaborating with Shell Oil to bring seven hydrogen refueling stations to northern California, including three in San Francisco. The California Energy Commission has awarded a $16.36 million grant for the installation of hydrogen options at existing Shell stations, and Honda and Toyota will provide further financial assistance. Both Honda and Toyota have introduced fuel cell vehicles that rely on hydrogen, namely the Honda Clarity and Toyota Mirai.