WASHINGTON — A new report by U.S. Inspector General Calvin Scovel says it’s difficult to determine whether the DOT’s Mexican cross-border pilot project is beneficial or harmful to the U.S.

The one-year project, which allows pre-selected Mexican carriers to haul beyond the longstanding 20-mile commercial restriction zone at the U.S.-Mexican border — has not attracted enough participants to draw a reliable conclusion, Scovel said yesterday.

Six months into the program, only 19 Mexican carriers have gained the authority to haul beyond the zone — far fewer than what’s needed to statistically determine reliable safety projections, Scovel told the U.S. Senate Committee on Commerce, Science & Transportation in Washington.

In fact, of the carriers that do participate, most don’t travel beyond the border zone they were previously confined to. “More than 90 percent of trips are inside commercial zones,” Scovel said.

Last week, John Hill, director of the DOT’s Federal Motor Carrier Safety Administration, said he wants to see the program extended because of the lack of Mexican participants. He complained that the prospect of having a San Francisco court cancel the controversial pilot project has scared off Mexican truckers.

Meanwhile, the latest inspector general report also noted that FMCSA hasn’t implemented a proper quality control measure for the program.

“Without this quality control measure, FMCSA does not have assurance that it has checked every Mexican truck and driver that is participating in the project when they cross the border into the United States,” the report said.