How long does cocaine stay in your system for a roadside test?
The honest answer //
Nobody can tell you. Not the police, not a calculator, not this site.
The limit isn’t set at “too impaired to drive”. It’s set barely above zero. So you are not waiting to be safe — you are waiting to be undetectable, and nobody can tell you when that is for your body.
That isn’t this page dodging the question. It is the actual position, and anyone who gives you a number is guessing with your licence.
If you came here at midnight wanting a number so you can work out whether tomorrow is alright, this page is going to be a disappointment, and it is going to be honest with you instead. What follows is what the law actually measures, why the numbers you will find elsewhere contradict each other, and what you can actually do with that.
What the law measures
It never asks how you feel
Since March 2015, Section 5A of the Road Traffic Act has made it an offence to drive with any of 17 specified drugs above a set limit in your blood.
It is a limit offence, not an impairment offence. The court does not ask whether you were a danger, whether your driving was affected, or how you felt. It asks what the blood sample contained. Feeling completely fine is not a defence. Driving perfectly is not a defence.
One of the 17 is benzoylecgonine, or BZE. It is not cocaine — it is what your body turns cocaine into, and it is named in the law in its own right, with its own limit. It stays in the blood long after any effect has gone.
That is the whole mechanism behind “sober and convicted”. It is not a loophole or a technicality. It is the offence working exactly as Parliament wrote it.
The official position on levels //
The Sentencing Council’s guideline for this offence states plainly that “it is not possible to draw a direct connection between the levels of a substance detected and the level of harm”, and that limits for illegal drugs are “set in line with a zero tolerance approach but ruling out accidental exposure”.
Sentencing Council, Driving or attempting to drive with a specified drug above the specified limit, effective 1 July 2023.
The two clocks
You’re reading the wrong clock
Clock 1How you feel
You can feel this one. It stops, and you know it has stopped.
Clock 2What a blood test finds
Keeps running after clock 01 stops. No end is marked, because nobody can honestly mark one.
Almost everyone decides “am I okay to drive?” using clock 1. It is the only clock you can read. The law only ever reads clock 2, and there is no version of you that knows what it says.
This is not a gap in this website. It is the actual scientific position, and it is why the answer at the top of this page is the answer.
Why there’s no BZE calculator
Why there’s no BZE calculator
People search for a BZE drug test calculator, a benzoylecgonine driving limit calculator, a drug driving calculator. We know, because that is partly how you got here. So here is why one doesn’t exist, and why we will never build one.
A calculator would have to predict what an evidential blood sample will contain at a future moment, for one specific body. Not an average body. Yours. That prediction cannot be made reliably, and a calculator that pretends otherwise is not a tool — it is a confident-looking guess with your licence attached to it.
And notice what such a tool would actually be for. It would not be for deciding whether you are safe. The limit is not set at the point of danger. It would be for estimating when you would stop being detectable. That is a different thing, and building it would make this site the exact problem it exists to warn people about.
Try this before you trust any number you find
Open the first four results for your search in four tabs and compare them. You will find different figures, different ranges, and different confidence levels — often on pages selling something.
They cannot all be right. There is no way for you to tell which one is, if any. And the one you are most likely to believe is the one that gives you the answer you want.
That contradiction is the finding. It is not that the internet hasn’t got round to answering this properly. It is that the question does not have the kind of answer people want it to have.
The one thing we will say with confidence is the thing at the top of this page, and it is worth more than a number: you are not waiting to be safe, you are waiting to be undetectable, and nobody can tell you when that is.
The test itself
The swab is the accusation. The blood is the verdict.
The roadside swab is a screening test. It flags. It convicts nobody, and it is not the evidence of the offence.
If it flags you are arrested, and a blood sample is taken at the station. Only the blood decides.
A swab can flag and the blood come back clean. It happened to the founder of this site: pulled over for a broken wing mirror, swab flagged, blood completely clear, no charge. The safeguard is real and it works.
If you are ever tested: comply calmly, say little, and remember the blood sample is the evidence that matters. Refusing to provide a specimen is a separate offence in its own right.
You stop trying to time it, because timing it is the thing that cannot be done. The rule that works is about separation, not hours:
If you use, you don’t drive on your own judgement of feeling fine.
Because your judgement reads clock 1 and the law reads clock 2. You cannot make this decision in the moment with the keys in your hand, because in that moment the only information you have is the wrong information.
So it gets decided in advance, or it gets decided badly. Decide before the weekend, not on the day: if there’s any chance, the car doesn’t come. And if you drive for work, who is driving Monday — sorted on the Friday.
If you drive for a living, the two things don’t go together at all. You’re not gambling a fine. You’re gambling your wage.