Because the "violation" rate for truck driver alcohol testing stayed under 0.5% two years in a row, the Federal Motor Carrier Safety Administration says carriers can continue to random alcohol test at a reduced 10% rate. However the rate for random controlled substance testing stays at 50%.

Under federal rules, the number of random alcohol tests a carrier administers in a year must equal 25% of eligible drivers. FMCSA has the authority to lower that to 10% if industry data, drawn from carrier reports, indicates a violation rate of less than 0.5% for two consecutive years. Although the violation rate has gone up, it hasn’t exceeded 0.5% since testing began. It was 0.14% in 1995, 0.18% in 1996, 0.2% in 1997 and 0.4% in 1998.
The number of random controlled substance tests given in a year must equal at least 50% of eligible drivers. FMCSA may lower that to 25% if the number of positive tests industry-wide falls below 1.0%. Approximately 2.6% of tests were positive in 1994, 2.8% in 1995, 2.2% in 1996, 1.3% in 1997, and 1.5% in 1998.