Truck drivers hauling water and sand to U.S. oil and natural gas shale drilling sites don't qualify for a special oil-field service equipment exemption to extend their daily driving hours.

The rule clarification, or regulatory guidance, from the DOT explains that time spent waiting while water and sand are unloaded at well sites counts toward the maximum 14 hours a day that a truck driver can work under hours of service regulations.

The guidance explains that the "waiting time" oil-field exemption in Sec. 395.1(d)(2), which allows these drivers to count waiting time is off-duty, is available only to operators of commercial motor vehicles that are specially constructed for use at oil and gas well sites, and for which the operators require extensive training in the operation of the complex equipment, in addition to driving the vehicle. In many instances, the operators spend little time driving these CMVs.

The clarification says that drivers of more typical commercial vehicles that haul water and sand in and out of these sites don't qualify for the exemption, "even if there have been some modifications to the vehicle to transport, load, or unload the materials, and the driver required some minimal additional training in the operation of the vehicle, such as running pumps or controlling the unloading and loading processes."

Yes, the DOT noted, these operators "may encounter delays caused by logistical or operational situations," but compared it to other motor carriers experience delays at shipping and receiving facilities.

The hydraulic fracturing process that has made possible a U.S. oil-and-natural-gas boom may require hauling as many as 1,000 truckloads of water and sand for every well.

A recent story on the front page of the New York Times highlighted the oil-field exemption, alleging the exemption's mis-use for drivers of all types of trucks working the oil fields was causing a large number of crashes.

The guidance explains that the other part of the oil field exemption, the 24-hour restart after 70 hours of work in eight days, does apply to carriers that provide direct support to oil and gas well sites, including hauling the water that is used in the fracking process, and hauling waste away from the site.

This new rule clarification limiting the 14-hour exemption may make it necessary for drillers to add drivers, Boyd Stephenson, director of hazardous materials policy for American Trucking Associations, told Bloomberg.

"If you were an operator in the past that was utilizing this exemption for transporting sand and water then, yes, it means you're going to have to have more drivers," Stephenson told Bloomberg. "There were probably some that were utilizing this exemption for sand and water trucks in the past. How many is anybody's guess."

You can read the Federal Register notice here.