WASHINGTON Just how difficult is it for commercial vehicle drivers to cheat on drug and alcohol tests?

Not difficult at all, according to federal investigators, and many small truck and bus companies are "overseeing their own substance abuse programs."

There was a Congressional hearing on the issue last month and the Government Accountability Office was asked to come back in May with suggestions for making improvements to federal drug test requirements and procedures.

Federal Motor Carrier Safety Administration data indicate that 1.3 to 2.8 percent of commercial drivers randomly tested between 1994 and 2005 tested positive for illegal drugs.

However, in two 72-hour sessions this year, Oregon roadside inspectors collected 500 urine samples from commercial drivers - mostly heavy-truck drivers and found an average of nearly 9 and 10 percent positive results. The Oregon samples had been tested anonymously, so follow-up was impossible.

Of course, there are other possible explanations for the Oregon rates, such as false positives and differences among testing methods, but the results suggest the problem may be more widespread than FMCSA figures indicate.

In February, the House Subcommittee on Highways and Transit heard a Minneapolis television station report that four of the five local USDOT drug test collection sites allowed ways to cheat on urine tests. Based on that report, the committee asked the GAO to conduct an undercover investigation.

Investigators invented two trucking companies, produced bogus driver licenses and then posed as truckers to test 24 collection sites nationwide. The GAO also interviewed all parties involved in testing, from carrier representatives to federal officials, and analyzed regulations and data.

By using their bogus driver licenses to gain access to the 24 sites investigated, the GAO investigators demonstrated that a drug user could send someone to take a drug test using fake identification.

Twenty-two of the 24 selected sites did not adequately follow the remaining protocols. For example, 75 percent of sites tested didn't restrict access to items that could be used to change the specimen, such as running water, soap or air freshener.

The GAO team also bought drug-masking products over the Internet and was able to mix them with real specimens at the drug-testing sites "without being caught by site collectors," the agency said.

Drug-screening labs never realized there was a problem. Every drug masking product went undetected by the drug screening labs.

The GAO investigators also found a significant lack of drug and alcohol testing compliance among carriers, particularly small operators and self-employed truckers.

Here's the problem: A one-vehicle bus or truck company still has to implement a drug and alcohol testing program. These companies usually do it using a third-party administrator. However, that administrator doesn't have the authority to enforce regulations if drug use is indicated.

According to the National Transportation Safety Board, these small carriers "are in the precarious position of overseeing their own substance abuse program."

Drug testing protocol violations are noted in more than 40 percent of FMCSA safety audits conducted since 2003 of carriers that have recently started operations and more than 70 percent of the compliance reviews conducted on carriers in the industry since 2001.

Even when FMCSA is able to ensure that carriers are in compliance with drug testing requirements, the urine test can be subverted. Drug masking products such as adulterants work well and destroy the evidence of their presence.

In 2005, the GAO testified that 400 products were marketed to mislead drug tests. Furthermore, the required test covers only five drug categories and it may provide a clean result if a person has not used any of these drugs recently.

Rep. Jim Oberstar, D-Minn., chairman of the House Transportation and Infrastructure Committee, who asked GAO to investigate, said the report was "frankly astonishing and shocking and dismaying. You can manipulate the tests, you can mask substance abuse and go undetected on the roadways."

Oberstar told one television network that the drug-testing system was broken and was placing other drivers in danger. "It fails, it is not sufficient, it is not protecting the public interest," he said.