The White House said at the time that it was confident haulage firms could cut emissions from heavy trucks by about 20 percent using existing technologies.

Now the EPA and DOT have lodged draft standards with the White House Office of Management and Budget (OMB) for review.

The OMB provided no details on the nature of the proposed rules, signaling only that it has received a draft proposal for “commercial medium- and heavy-duty on-highway vehicles and work truck fuel efficiency standards.”