Police and scientists have developed a handheld device for frontline officers to test for methamphetamine, MDMA and cocaine.

The real-time drug-screening tool allows officers to test for "the three most harmful and commonly used drugs on the New Zealand market" while "working in our communities", police said in a statement.

A six-month trial of the devices will be carried out across Auckland as well as in Canterbury and Central Police Districts.

Acting Assistant Commissioner: Investigations Mike Johnson and forensic research and development project manager for ESR - New Zealand's Crown research institute - Dion Sheppard will demonstrate the device at ESR offices in Auckland tomorrow.

In December, the Government announced it would give police new powers to conduct random roadside drug testing and to prosecute drugged drivers in a bid to save lives on the road.

The new rules – to go through Parliament this year – mean the police will be able to conduct oral-fluid drug testing on drivers.

They are expected to come into force in early 2021.

Any drivers who test positive for the presence of drugs will be fined and immediately suspended from driving for a minimum of 12 hours.

"The change will allow police to test drivers for the presence of drugs and impairing medication anywhere, anytime, just as they can for alcohol," Associate Transport Minister Julie Anne Genter said at the time.

Drivers will also face criminal penalties if they fail a compulsory impairment test and blood tests confirm impairing levels of drugs in their system.

In 2018, 95 people were killed in preventable crashes where the driver was found to have drugs in their system that could impair driving.

Genter said the saliva tests would take between two and five minutes to process, but they were not foolproof.

The devices were known to give false positives, so people who tested positive would be tested a second time before facing a fine and an immediate suspension from driving for a minimum of 12 hours.