Device is more accurate than current tests, and uses saliva to reveal levels of cocaine in drivers’ systems

Scientists have developed a new roadside test for cocaine in an effort to improve driver safety.

The device is an improvement on current tests, avoiding the problem of false positives, and can offer insights into how much of the drug drivers have taken.

“Drug-driving is an increasing problem,” said Melanie Bailey of the University of Surrey and co-author of the research published in the journal Analytical Methods. “We want to try to improve safety on the roads and this is one way to do that because we will be able to monitor a larger number of people without wasting their time by getting false positive results.”

Nearly 8,000 people were arrested for drug-driving in England and Wales between March 2015 and April 2016, with cocaine and cannabis among the illegal drugs tested for.

While roadside tests for cocaine already exist in the form of antibody-based kits the approach, researchers say, cannot reveal how much cocaine a driver has taken and can give false results.

“The antibody binds to the drug that is of interest and then you get the positive result, but the problem is that antibody can also bind to things that are not cocaine, so you can get a false positive signal - for example, certain kinds of antibiotics,” said Bailey. “In about 5% of cases you will get a test result that is positive when actually the person hasn’t taken cocaine.”

The new device uses a dual approach to analyse a swab of saliva from the driver’s mouth. The chemicals in the sample are separated using chromatography - the same technique that can be use to separate ink with blotting paper and water. The mass of the chemicals and their fragments are then analysed to reveal whether cocaine is present. The device, says Bailey, is based on a robust laboratory technique that has been miniaturised to produce the portable roadside test.

While Bailey adds that each new device costs upwards of £30,000, compared to £5 per current roadside test, she is confident that the approach will prove cost-effective in the long term. “Over a year, even, the number of tests that you would carry out would pay for itself,” she said.