The "violation" rate for random alcohol testing of truck drivers was 0.2% in 1999, down from 0.4% in 1998 and low enough to maintain a reduction in the number of tests required.

The positive rate for controlled substances (drug tests) was 1.3%, a slight improvement over 1998’s 1.5%, but still not low enough to earn a reduction in the test rate.
Under federal rules, the number of random alcohol tests administered each year must equal 25% of eligible drivers. However, the Federal Motor Carrier Safety Administration 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. The violation rate was 0.14% in 1995, the first year of alcohol testing, 0.18% in 1996, and 0.2% in 1997.
The number of random drug tests given annually must equal at least 50% of eligible drivers. FMCSA may lower that to 25% if the number of posititive tests industrywide falls below 1%. In 1994, the first year of testing, the industry positive rate was 2.6%. It was 2.8% in 1995, 2.2% in 1996, 1.3% in 1997, and 1.5% in 1998.