WASHINGTON – In light of four new fatigue studies "surfacing," the Federal Motor Carrier Safety Administration said it has reopened the hours-of-service Notice of Proposed Rulemaking comment period to allow for further review of the new research.

The agency did not indicate how long it extended the additional comment period. However, FMCSA reportedly must post a final rule by July 26.

FMCSA says it is committed to" receiving and analyzing all public comments on the studies" before it completes its work on the final rule.

The studies – which can be viewed here – seem to indicate that safety risk increases as work and driving time increases.

On its website, the American Trucking Associations – a vocal critic of the FMCSA's plan to change the current HOS rule -- said it was "intrigued" by the "unusual announcement" to reopen the docket, but it remains "skeptical about the 11th-hour appearance of the research."

"ATA believes decisions about the future of this important regulation should be made based on sound science and research and not political pressure, but we're clearly skeptical of new research that has been discovered or generated by DOT at the '11th hour," said ATA president, Bill Graves.

ATA has called for a review of the science behind the FMCSA's changes. It insists that there are "serious questions about the research and data used by FMCSA to justify its proposed changes to the regulations."

A key sleep researcher, whose work was used by FMCSA to support the changes, claims that the agency may have misused his data.

At the behest of the ATA, Edgeworth Economics also conducted an analysis of the proposal and determined, among other flaws, that the FMCSA grossly overstated the net benefits of the proposed changes.