A government report has found no improper influence by the auto industry in safety defect investigations conducted by the National Highway Traffic Safety Administration.

The report covered former NHTSA employees who went to work for the auto industry as well as former auto industry employees who left for NHTSA.

"We found no evidence that the former employers influenced the [Office of Defects Investigations] employees in deciding whether to upgrade or close the cases," Calvin Scovel, the U.S. Department of Transportation inspector general, wrote in an April 4 letter to two Senators who requested the investigation. The letter was posted on the Department of Transportation’s Web site, reported Automotive News.

Sen. Mark Pryor, D-Ark., and Sen. Jay Rockefeller, D-W.Va., asked for the study in the wake of NHTSA’s review of sudden acceleration claims in Toyota Motor Corp. vehicles. The review revealed that two former NHTSA officials were now working for Toyota and dealing directly with the administration.

Christopher Tinto, vice president of regulatory affairs in Toyota's Washington office, and his employee Christopher Santucci helped persuade NHTSA to end probes into some Toyota vehicles, according to government documents surrounding the unintended acceleration case. Santucci said he had worked with NHTSA to determine the scope of the investigation. Tinto left NHTSA in 1994 and Santucci in 2003.

The inspector general’s study contradicts those allegations.

“We are pleased this study has confirmed the professionalism and integrity of those in the public and private sectors who work cooperatively and openly to enhance safety,” Toyota said in a statement.

Toyota is only one of many automakers to employ former NHTSA officials.

Since 1984, 40 NHTSA employees left to work in the auto industry, Scovel wrote in the letter. Of those, 15 departures occurred in the past 10 years. He also reviewed 65 cases that went through the Office of Defects Investigations during that time.

Investigators based their determination on statistical analyses of cases and from interviews with administration employees.

In his letter, Scovel said most former NHTSA employees went to work for automakers or law firms that represent the auto industry. These include Toyota, Honda, Nissan, and Volkswagen, he said.

Scovel also found 23 cases of individuals leaving the auto industry for NHTSA since 1984. But this, too, did not influence defect investigations.

“Overall, we found no evidence suggesting undue influence or pressure on NHTSA’s employees conducting safety defect investigations, and NHTSA had adequate controls in place to ensure employees’ compliance with ethics requirements,” Scovel wrote in the letter. “Additionally, NHTSA officials complied with U.S. Office of Government Ethics rules for employee training, financial disclosure reviews, and ‘cooling-off’ periods for current employees who previously worked for automakers.”

NHTSA employees are required by law to wait two years before going to work in the auto industry.

Some lawmakers have complained about the “revolving door” between NHTSA and the auto industry. Last April, Sen. Barbara Boxer, D-Calif., even introduced legislation that would require top NHTSA officials to wait three years before taking employment in the auto industry. The bill, which was supported by former NHTSA administrator Joan Claybrook, has since stalled in committee.