Dale Dunster and other medicinal cannabis users in NSW would no longer need to fear losing their driver's licence if proposed laws were passed.
The Legalise Cannabis Party will on Wednesday introduce a bill to state parliament that offers prescribed medicinal cannabis users a defence to roadside drug testing laws.
The proposal would not apply if the driver was impaired.
Mrs Dunster, who has Parkinson's disease and a lung condition, says the defence would mean she could get behind the wheel without having to plan out the medicine that makes her "feel normal".
"It plays on my mind if I have to go anywhere," the 73-year-old from Ballina in northern NSW told AAP.
"Tomorrow, I have to drive to the Gold Coast, so I'm thinking I won't be able to have the (cannabis) oil tonight."
Her son James, a demolition company supervisor, resorts to medication other than cannabis oil to treat his epilepsy unless he is certain he won't be driving in the coming days.
"It's very difficult when you know you might get pulled over and therefore lose your job," Mrs Dunster said.
Roadside drug testing in NSW looks for the presence of ecstasy, cocaine, methamphetamine or the psychoactive component of cannabis, THC.
Unlike breath testing for alcohol, the law ignores the drug's impact on driving and in the case of cannabis, whether it has been prescribed as a medicine.
Those caught face three months off the road and a $603 fine while repeat offenders are liable for automatic licence disqualifications.
No other prescription drug is unfairly penalised in this way by law enforcement, Legalise Cannabis MP Jeremy Buckingham said.
"The issue here is that cannabis remains detectable long after any impairment to driving has ceased," Mr Buckingham said.
"These unfair laws are specifically harsh for those in regional, rural and outer suburban areas where public transport is simply not an option."
While THC-free cannabis oils are available, Mrs Dunster said they cost about twice as much per dose.
New Zealand, the United Kingdom and Germany were among the jurisdictions with exemptions for cannabis oil patients without any apparent problems, University of Sydney psychopharmacology professor Iain McGregor said.
"This (NSW proposal) would simply put the legislative approach with medicinal cannabis on an even foot with other prescription drugs that have the capacity to impair driving," he said in a statement.
A similar bill introduced by Legalise Cannabis MPs in Victoria is currently before that state's upper house.
