Stronger fuel economy standards and federal tax incentives for electric vehicles are top recommendations for how the country will cut the energy usage in the transportation sector in half by 2050 from an auto and utility group.

Audi AG, General Motors Co., and the Southern Co. are among 24 companies and environmental and policy groups that were part of the 50x50 Commission, which released a report on the energy cuts Sept. 26.

The report suggests...