Science Interviews


Tue, 22nd Dec 2015

Driving home (sober) for Christmas

PC Andy Coop, Beds, Cambs & Herts Roads Policing Unit

Listen Now    Download as mp3 from the show Cracking the science of Christmas

Drinking impairs most of your motor-functions, but also your ability to analyse howBrandy drunk you actually are. This can be a massive risk over the festive season, with people electing to drive when they are over the legal limit. The Naked Scientists are caught drinking by PC Andy Coop, armed with his trusty breathalyser, who explained just how the police try to prevent drink driving over the holidays.

Andy - A high percentage of people who come into contact with the police the following morning are unaware that they're driving in excess of the drink/drive limit.

Chris - Now Adam - we actually gave you a rather interesting Christmas present here on the show and you drank a pretty healthy half bottle of your Christmas present - you have consumed brandy.  Did you feel impaired at all?

Adam - Well, I feel quite smooth.  PC coop is making me doubt myself.

Chris - How did you think the interview went?  Did you feel impaired at all?

Adam - I thought my interview went very well, thank you.

Chris -   So, you would have been comfortable probably to drive yourself home, do you think, this evening if you'd been in the car?

Adam - No.  I feel a bit hazy so I think I would have relented or taken the train or something like that.

Chris - Are you just saying that because you've got  police officer sitting opposite you?

Adam - No sir.

Chris - But this is about the size of a big mobile phone and it has a pipe that you've just attached sticking off the side of it.

Andy - This is a Dreger roadside screening device that we as the police carry in Cambridgeshire and, basically, it's a screening device.  It give us an indication as to whether the individual we've stopped at the roadside is over the drink/drive limit.

Chris - How does it actually work?  What's it measuring on Adam when we do it?

Andy - When Adam blows through the tube, it's timed to allow him to blow long enough through the device to get the air from within the bottom of his lungs, so it's not taking the air from within his mouth that's obviously a stronger content of alcohol.  So we're looking at what's already been absorbed in his system.

Chris - So, basically, the alcohol that's in your blood, Adam.  Some of that alcohol dissolves in the air in your lungs and so when you breathe out nice and hard and blow into this wonderful device, you're going to impart some of the alcohol in you into the device.  Do you want to pretend you've just stopped Adam then, Andy and take him through the procedure?

Andy - Okay. Hello sir so obviously we've stopped you this evening.  You've come through out drink/drive checkpoint.  Now have you had any alcohol to drink today?

Adam - Yes...

Andy - Yes, okay.  I can smell it on your breath anyway as I'm talking to you.  So I'm going to require you to provide me with a specimen of breath.  I must tell you that failing to provide me with a specimen of breath, along with a positive specimen will render you liable to arrest and subsequent prosecution.  Okay, do you understand what I've said?

Adam - Yes sir.

Andy.  Okay.  Just seal your lips around the tube.  Form a nice seal and blow long and hard through the device until I say stop.  So, when you're ready, blow.  Keep going, keep going, keep going, stop!  Thankyou.  So that will analyse the breath that you've provide me now and then we'll get a reading up there.  You've actually passed the test but it has detected that you've drunk alcohol.  So, on this occasion we'd obviously let you carry on your way but with words of advice.

Chris - It says 22 micrograms per 100mls.  What does that mean?

Andy - That says that that's detected 22 micrograms of alcohol in his breath.  So, obviously, the legal limit is 35 so at 22 micrograms of alcohol is an allowed level for him to drive albeit it does detect alcohol in his system.

Chris - Georgia's had a little bit to drink a little bit more recently.  So do you want to have a go Georgia and just see how more recent consumption affects you?  How much have you had?

Georgia - I think I've had slightly less than Adam has but yes, I've been enjoying a bit of brandy.

Chris - I can smell it!  As PC Coop says, you can definitely smell it.  The whole studio stinks of brandy now.  I hope you gave her permission to help herself.  She's been stealing, stealing your brandy.

Georgia - It was a stressful show. 

Andy - I'll just go through the preamble on the machine.  That's where we would normally enter the subject's gender, their age and the reason for which we're obtaining the specimen.  So, that's ready to go, so seal your lips around the tube and blow until I say stop.  Stop!  And again, because that hasn't immediately returned to zero reading, that's detected alcohol in your breath.

Chris - Ooh! There's these massive black letters that say fail.  Ohh! 44 - that's well over Georgia.  How much did you have?

Georgia - I didn't think I had that much.

Andy - That's accompanied, obviously, with the red indication light there for people to see that they've failed.  So if you'd been stopped by us on one of our checks or for something as simple as a stop light out, or a headlight out, you'd find yourself being arrested now and taken to Police Station.

Chris - Good grief!  Is it possible that it could do a false positive?

Andy - No.  Because we would get to the bottom of that.  This is a screening device.  They would come under on the evidential machine in the custody suite.  But if we're going on what we saying Georgia has drunk earlier in the evening then, obviously, that just shows you that her body's dealing with the alcohol content differently.  And if we're saying that they've both drunk the same that's put her over the limit, whereas the other test was under.

Chris - Are you surprised?

Georgia - I'm really surprised.  I thought I had a lot less than Adam did and I feel fine as well.  So, I don't think I'd have hopped into a car but I'm quite relieved it's not illegal to drink and radio.


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