Here’s something most people don’t know yet about cannabis and driving.

Scientists have already solved the key question: ‘when does impairment wear off?’

Scientists have now spent years studying exactly when and how the THC in cannabis affects your ability to drive. And they’ve found something important: even though cannabis affects people differently, the timeline for when driving ability returns has been studied extensively, and it’s now well understood.

So science can now tell us the timeline of when impairment clears.

For most people:

• using inhaled products, driving ability is back within three to five hours. 
• for oral products, driving ability is back within eight to ten hours

That finding holds across dozens of studies, different doses, different people, multiple countries.

In other words: if you’ve taken your medicine and waited for the effects to wear off, you are not an impaired driver. Science can prove it. The law just hasn’t caught up yet.

And right now, it looks like the law in NSW is about to catch up – at last! The Premier has publicly acknowledged the current system isn’t fit for purpose, and NSW Parliament sits on 17 March. Reform is close – which means this is the moment to understand what the science actually says.

So why are sober patients still banned from driving?

Hundreds of thousands of NSW residents have a valid prescription for medicinal cannabis. Every single one of them is banned from driving. Not just when they’re affected. All the time.

Here’s why. The current law is zero tolerance – any trace of THC at all, no matter how small, no matter how long ago you took your medicine. And because THC residue stays in your body for days, sometimes weeks, long after any effects have worn off, there’s no way for a patient to know if they’re still detectable. Even completely sober. Even having waited. Still banned.

NSW Police’s own procedures confirm it: their saliva tests do not test for impairment. A patient who took their prescribed cannabis Tuesday night, waited for it to wear off, slept a full night, and drove to work Wednesday morning is committing a criminal offence. Not because they’re impaired. Just because they have residue in their system.

That’s not road safety. That’s a blanket ban on driving for people with a legal prescription.

And it’s making our roads less safe. Around one in five crashes is thought to involve fatigue. But right now, doctors can’t properly advise patients with insomnia to try medicinal cannabis – because the law bans them from driving if they do.

So patients stay on sleeping pills that either don’t give them enough sleep to drive safely, or leave them groggy the next day – just because those pills don’t come with a driving ban.

The “we can’t measure impairment” argument is out of date

When people push back on changing this law, the argument usually goes: ‘we can’t reliably measure impairment at the roadside, so we can’t safely let patients drive.’

Here’s what that argument gets wrong:

Scientists have already mapped when impairment clears – and the timeline is consistent enough to build a law around. That changes what we need from a saliva test entirely. Detect any trace of THC at all? Useless – residue hangs around for days whether you’re impaired or not. 

But set the cut-off high enough, and a saliva test can tell you something that actually matters: whether someone used cannabis recently. And recent use is when impairment is most likely. We don’t need a perfect test. We need a law that uses what we already know. The current law doesn’t. Most of the rest of the world has moved on.

And NSW wouldn’t be starting from scratch. Look at how the rest of the world handles this. In country after country, a patient cannot be convicted simply for having cannabis residue in their system. Not the UK. Not Germany. Not Norway. Not the US states that have reformed their laws. Even Tasmania, right here in Australia – gives patients a legal defence.

NSW is the outlier. We are one of the only places that will prosecute a patient purely for traces of residue, even when they’re completely unimpaired.

Once you know that, the ‘we can’t measure impairment’ argument lands differently. We don’t need to ban patients from driving, we just need to make sure they know how long to wait.  

The science moved. The law hasn’t.

Yet.

The litmus test for whatever gets announced

When the details land, there’ll be noise. Opponents will say it goes too far. Some supporters will worry it doesn’t go far enough.

Here’s the only question that actually matters:

After this reform, if a patient with a valid prescription takes their medicine, and waits for the effects to wear off, are they still banned from driving?

• If the ban is really no longer in place, that’s real reform, let’s get behind it!
• If yes, still banned, then it’s not good enough, and we keep pushing.

One thing you can do right now

Parliament sits on 17 March. Before the details drop and the debate gets loud, make sure your MP knows where you stand.

The current law was written before medicinal cannabis was even legal in NSW. It still treats a valid prescription like an illicit drug. Patients who wait for impairment to wear off shouldn’t be criminalised for taking their medicine. That’s not a radical ask – it’s what we already expect for every other prescribed medication.

Email your MP now and tell them: real reform means patients can drive safely and responsibly without being punished for following their doctor’s advice.

Email your local MP

Know a patient, a carer, or someone who’d want to understand what’s at stake before this gets announced? Send this to them. The more people who go into this informed, the better the outcome for everyone.