American Trucking Associations is suing to overturn the new hours of service rule. ATA is asking the U.S. Circuit Court of Appeals for the District of Columbia to set aside the Federal Motor Carrier Safety Administration rule as arbitrary and capricious.

"We regret that FMCSA and the Obama administration have put ATA and its member companies in a position to take this legal action," ATA President and CEO Bill Graves said in a statement.

"The rules that have been in place since 2004 have contributed to unprecedented improvement in highway safety. The law is clear about what steps FMCSA must undertake to change the rules and we cannot allow this rulemaking, which was fueled by changed assumptions and analyses that do not meet the required legal standards, to remain unchallenged."

ATA said the agency overstated the safety benefits of the new rule, and that the costs outweigh the claimed benefits.

"We need this issue to be resolved in a credible manner, taking into account the undisputed crash reduction since 2004, so we can focus limited government and industry resources on safety initiatives that will have a far greater impact on highway safety," Graves said.

ATA's move opens up another front in the long-running war over the hours of service rule.

A highway bill in the House of Representatives contains a provision that would require FMCSA to study and possibly rewrite the 34-hour restart provision of the rule, which limits the restart to once a week with two sleep periods from 1 a.m. to 5 a.m. Whether or not the bill will pass in its present form is anyone's guess, however.

Truck safety advocacy groups and the Teamsters union have yet to say if they will renew their own legal action against the new rule, although they have indicated strongly that they will.

It was their suit against the rule that pushed the Department of Transportation to do the rewrite that came out last December. They agreed to suspend their suit while the agency reviewed the rule, but reserved the right to renew their suit if the rewrite was not satisfactory to them.

The key issue for them is the 11-hour daily driving limit, which the new rule preserves. The agency said that while it will continue to study a cutback in the 11-hour limit to 10 hours, at this point there is no "compelling scientific evidence" that the 10-hour limit produces enough safety benefits to outweigh the higher net benefits of the 11-hour limit.

Advocates for Highway and Auto Safety has indicated that it may resume its challenge of the 11-hour limit. Last December when the rule came out, the group said it is confident that since the appeals court has twice rejected the 11-hour provision it will do so again. Henry Jasny, the group's vice president and general counsel, said that barring the unexpected the group probably will renew its suit.