When the researchers drafted their report, they included a key suggestion: The DOT should craft federal regulations requiring side guards.

But that recommendation generated intense resistance, both internally, from department officials who challenged their findings, and externally, from trucking industry lobbyists.

... the department supervisor overseeing the project had a very direct message for the researchers. “PLEASE delete any mention of a recommendation to develop … any regulation,” he wrote in an email. “An industry standard is acceptable, but no mention of ‘regulation.’”

The industry objections resulted in a remarkable concession from the department: It allowed trucking company lobbyists to review the researchers’ preliminary report and provide comments on it.

By the time of its release in 2020, the report had been dramatically rewritten, stripped of its key conclusions — including the need to federally mandate side guards — and cut down by nearly 70 pages.