Carmakers in the US have considered implementing fuel economy standards as high as 36mpg for cars and 30mpg for light trucks as an alternative to new regulations that could be voted in by the full Senate the week of June 11. The proposed Senate bill would force carmaker’s fleet average fuel economy rates up to 35mpg by 2020, up 40% on current levels, and additional increases of 4% per annum until 2030.

Most in the auto industry including lobbyists agree that the bill is too harsh, and have instead put forward a draft of alternative legislation prepared by Detroit Senator Carl Levin. Under his proposal, carmakers would introduce a car standard of 36 mpg by 2022 and a truck standard of 30 mpg by 2025, reports Automotive News.

The draft proposal would allow carmakers to circumvent fuel economy standards as long as they show that they’re developing vehicles with lower fuel consumption and emission levels.

Environmental lobbyists are against Levin’s bill, which they say is plagued with loopholes that would lower set standards if they’re deemed too tough by regulators.