While the U.S. economy continues to improve in 2016, putting more freight and more drivers on the highways, the federal arm overseeing trucking has reduced the number of random drug tests required of big rig drivers.

This hardly makes sense. Substance abuse continues to be a serious problem in the industry. Yet, the Federal Motor Carrier Safety Administration on Jan. 1 lowered the rate of random testing for controlled substances from 50 percent to 25 percent of the average number of driver positions.

The FMCSA has the authority to lower the rate of testing when results have shown those testing positive for drugs holds steady below 1 percent over two years. Federal data show that has been the case for 2011, 2012 and 2013. If the percentage of truckers testing positive rises above the 1 percent threshold again, then the motor carrier administration can again increase its spot checks.

While the recent trend line for positive tests is encouraging, the low percentage fails to account for those drug-abusing drivers who remain on the highway unchecked. There really should be zero tolerance for controlled substance use among drivers of these huge, dangerous vehicles crowding interstates across America. As for alcohol testing, the minimum annual random testing rate remains at 10 percent.