What to expect during a roadside breath test?

As described in our article on “are random drink or drug tests legal”, you can be asked to undergo a roadside breath test if either:

  • The officer reasonably suspects you’ve consumed alcohol;
  • The officer reasonably suspects you’ve committed a motoring offence;
  • You’ve been involved in an accident.

There are currently fifteen, home office approved roadside breath testing kits in use on Britain’s roads. The below are the instructions that are typical to most devices in use today.

What should happen during a roadside breathalyser test?

You should be asked when your last drink was. The police officer should wait at least 20 minutes before conducting the roadside breath test after your last drink. Officers typically wait 2-5 minutes after your last cigarette.

The officer should attach a fresh mouthpiece to the breathalyser and should explain the test to you. The officer should instruct you to fill your lungs and blow in one continuous breath through the mouthpiece.

In some cases, you’d have to blow strongly enough to bring on light A, and long enough to bring on light B. If you fail to bring on light B then you’d be deemed to have provided an unsatisfactory sample. In other cases, you’d need to cause the machine to create a continuous beep whilst blowing and would have to stop once you hear a double beep. It all depends which type of breathalyser device you blow into.

In under a minute, the officer will take the reading from the machine.

A green light, or the words “Zero” or “Pass” means you’ve hardly got any alcohol in your system and you’ve passed the test. You can go on your way.

An amber light, or the word “Warn” means you’ve got more alcohol in your system, but you’ve passed the test. You’ve been lucky and should go on your way.

A red light, or the word “Fail” is bad news. You’re over the limit and will be taken to the police station for evidential testing.

The do’s and don’ts of roadside tests that the police should adhere to:

Your knowledge of these procedures could help establish whether the police have breached procedure, and whether or not the roadside breath test result can be challenged by your legal team.


  • Ensure that it has been at least twenty minutes since the driver’s last drink before performing a roadside breath test;
  • Allow at least two minutes since the driver’s last cigarette before performing a roadside breath test;
  • Use a new mouthpiece for every test;
  • Ensure that a “ready check” is obtained before performing the breath test;


  • Allow the driver to hold the breathalyser device themselves;
  • Allow tobacco smoke to be blown into the mouthpiece;
  • Store the breathalyser device in an environment that is too hot or too cold;
  • Don’t subject the machine to severe mechanical shock (e.g. throwing it on the ground).

If you’ve been subjected to a breath test and you think the police have failed to follow the above guidelines, please contact a member of our legal team as soon as possible on 0330 33 22 770. There are numerous defences to drink driving, whether the police have breached procedure at the roadside, police station or hospital. It may not always be obvious that the police have made a mistake, so it’s vital to gain expert opinion on whether you have a case to fight. It could make the difference between walking away from Court with your licence intact or facing a minimum twelve-month ban from driving and a criminal record.

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Article written by Alison Ashworth, Specialist drink and drug driving solicitor and Managing Director of Ashworth Motoring Law. Alison has a first-class honours degree in law and has appeared on various TV and Radio programs to discuss drink and drug driving. Widely considered the “go-to” expert in the field of motoring law, Alison has outstanding rates of securing not guilty verdicts in cases involving drink and drug driving. Contact 0330 33 22 770 for an initial opinion on your case for free today.

Random stop for breath test or drug test

Another of our clients found Not Guilty of Drink Driving; Testimonial

Making our clients happy, fighting against injustice and getting the right result in every case is what gets us out of bed in the morning and keeps us working late at night.

It’s why we do what we do.  We are always delighted when we receive testimonials from satisfied clients for whom we have secured a phenomenal result.

Here is our latest testimonial from a very happy client of ours who has been found Not Guilty of Drink Driving:

Ashworth Motoring Law Happy Client Testimonial

“I am writing this review in relation to my experience with Ashworth Motoring Law. Being in a position where your faced with losing your license or even prison is not a nice place to be. I did an extensive amount of research and contacted numerous solicitors for free phone consultations and just didn’t find the comfort or reassurance i needed to decide whether to part with my hard earned money or stay with a legal aid firm. It was a big decision that could affect my career and day to day life for the next few years to come. I finally got around to speaking to Alison and something just felt different about how she came across and it was pleasantly reassuring. I made the choice to go with Alison and she accepted my case. I had been charged with a drink drive offence and also an allegation of failing to stop for the police. The police and prosecution are there to just get targets and numbers up on convictions, no matter if they think you are guilty or not. That is one thing i have learnt in this. Without Alison i would not have stood a chance in hell and the police kept trying to add new things in to worsen things for me, but Alison pursued and fought and worked twice as hard as them to get the result I needed. Im normally quite smart with most things, but Alison can find a diamond in the rough instantly in every instance.  

From the beginning Alison and Colette advised and helped me and kept me more then up to date with everything that she was doing in relation to my case. They put my mind at ease all the way through. They made me feel like it was my good friends on my side helping me in a situation where someone else is trying to ruin my life. Alison was amazing and got me one of the best barristers around. We went to court and successfully walked out with not guilty verdicts to both charges. I couldn’t have been more happy and am able to continue my life normally now. I really am glad i followed my instinct and went with Ashworth Motoring Law.  

If you find yourself in any similar driving position and are a little sceptical about using a private solicitor as opposed to legal aid then I am more than happy to speak to you about my case as an independent person and I’m happy to answer any questions you have. I feel i owe Alison the respect to do that after how much she did to help me and successfully at that. I have unfortunately experienced the services of a legal aid solicitor in the past and to be honest there is no comparison and they of course left me high and dry and with an unsuccessful case i received a conviction. This is what made me more used towards paying for legal representation. They are just lazy number crunchers who want a big turn around of clients whether they help them or not. Ashworth Motoring definitely provide the whole package and more.  

If you do wish to contact me please do not hesitate to ask Alison or Colette for my details. Once again thank you to all at Ashworths.”

Mr B, Birmingham.

Why we do what we do:

At Ashworth motoring law we are dedicated to keeping drivers on the road. We believe that no driver’s licence should be placed in jeopardy due to a lack of legal or technical knowledge. That’s why we’re always striving to deliver relevant, current content to keep you up to date with issues that could affect your freedom to drive.

We know the devastating impact that a disqualification from driving could have on a person’s life, career and family. It’s from that understanding that we fight to save the driving licences of motorists throughout the Country, to ensure that no person is disqualified where a valid defence or judicial discretion is available.

If you’ve been unlucky enough to be accused of drink driving or any other motoring offence and need to keep your driving licence, you can call one of our team of Expert Motoring Lawyers at any time on 0330 33 22 770 or email enquiries@ashworthmotoringlaw.co.uk. Our specialist driving offence solicitors will listen to the details of your case and let you know instantly if your licence could be saved.