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There are calls for NSW Police to reform roadside drug testing following claims Australian drivers are being punished when they’re not under the influence of drugs.

NSW Greens MP and spokeswoman on drug law reform, Cate Faehrmann, has slammed the state’s approach to roadside drug tests, branding it “arbitrary and unreliable”.

Some drugs can be detected for up to 30 days after use, meaning motorists can face a massive fine and disqualification even if there is no evidence they are being impaired by such drugs.

“Imagine losing your license for driving after having a beer a couple of days ago,” Ms Faehrmann said.

“It sounds ridiculous, but this is exactly what is happening to people who might smoke a joint and drive a few days later.”

Marijuana is one of the drugs that can stay in a person’s system for a significant amount of time, even after the effects have worn off.

It can be detected in urine for up to 30 days after use for frequent users.

For those who rarely use the drug, marijuana can still stick around in their system for about three days.

MDMA can be detected for up to three days and speed or ice can be detected for as long as five days, depending on the amount taken.

For frequent users, cocaine can be detected in urine for up to two weeks after being used.

For others, it can register for two days after use.

Ms Faehrmann said the current procedure used by NSW for roadside drug tests had “nothing to do with improving safety” and was merely an outcome of the failed war on drugs.

“The current regime is unfairly wrecking people’s lives, clogging up our courts, costing enormous amounts of money and wasting police resources,” she said.

The NSW Greens want the system reformed so drivers aren’t punished weeks or months after taking an illicit substance.

They are calling for a new evidence-based program to be developed that tests for impairment rather than just the presence of drugs.

MP Tamara Smith backed the change, saying the current system isn’t fair on NSW drivers.

“The war on drugs in NSW has been extended to roadside drug testing where the mere presence of a drug rather than an impairment test is being used to arrest drug users who may have imbibed weeks before the test but the substance is still in their system,” Ms Smith said.

“The question needs to be asked — Is a driver who has smoked a joint a week ago an impaired driver?

“Let’s use the science to find out the answer and then communicate that to the public.”

From July 2015 to June 2016, almost 10,000 people were charged with drug-driving offences in NSW.

Of those offenders, 98.3 per cent were found guilty, according to the NSW Bureau of Crime Statistics and Research.

There also appeared to be a disproportionate number of drivers being convicted in the Richmond-Tweed area, with 470 convictions per 100,000 drivers.

This is more than five times the NSW average of 92.9.

Driving with the presence of cannabis, ice, MDMA, cocaine or morphine in your system can result in a $1100 fine and up to six months disqualification for a first-time offender.

A repeat offender faces a $2200 fine and an automatic disqualification period of 12 months.