Section 4 of the Road Traffic Act 2010 – Drink Driving Explained in Plain English

Patrick Horan
Apr 17
3 min read

Updated: Apr 26

If you or someone you know has been arrested for drink driving in Ireland, chances are the charge is based on Section 4 of the Road Traffic Act 2010.

This is the main law that deals with drink driving. The problem is — it’s written in complicated legal terms that are hard to understand.

This article breaks it down into plain English so you know exactly what the law says, what it means for you, and what could happen next.

"Lesson?

Keep your licence on you at all times.

It might make the difference between

being arrested for drink driving and driving home"

What Does Section 4 of the RTA 2010 Actually Say?

Section 4 makes it an offence to drive — or even try to drive — a mechanically propelled vehicle in a public place:

If you are under the influence of an intoxicant, and
If you are over the legal limit for alcohol in your system (blood, urine or breath)

There are two ways to be found guilty under Section 4:

You're clearly unfit to drive because you’re appear drunk, or
You’re over the legal alcohol limit.

The Legal Limits – What Counts as “Over the Limit”?

The Act sets out strict alcohol limits in:

Blood
Urine
Breath

There are two sets of limits:

One for most drivers
One for “specified persons” (learner drivers, newly licensed drivers, and professional drivers like bus/taxi/truck drivers)

Here’s a simple table:

Type of Driver	Blood	Urine	Breath
Regular Driver	50mg/100ml-	67mg/100ml	-22mcg/100ml
Specified Person	20mg/100ml-	27mg/100ml	-9mcg/100ml

If you fall under the “specified person” category, you’re held to a much lower threshold.

Even one drink can put a specified person over the limit.

Who Counts as a “Specified Person”?

According to the Act, you are a specified person if you:

Have a learner permit
Got your first full licence less than 2 years ago
Drive professionally (e.g. bus, taxi, truck)
Are driving without a valid licence
Fail to produce your licence when requested by Gardaí

If you don’t show your licence during a roadside test, you’ll be treated like a specified person — and the lower limits apply at the roadside.

Lesson?

Keep your licence on you at all times. It might make the difference between being arrested for drink driving and driving home.

Garda powers under section 4

If a Garda believes you are driving (or trying to drive) while impaired:

They can arrest you on the spot — no warrant needed
They can take you to the station for an evidential test (breath, blood, or urine)
If you're found to be over the limit (i.e. you fail the breath test in the station), you’ll be charged with a Section 4 offence i.e. drink driving.

What Are the Penalties?

A person convicted under Section 4 faces:

A fine of up to €5,000
Up to 6 months in prison
A mandatory disqualification from driving (the length depends on how high your reading was)

And here's something most people miss:

You cannot get the benefit of the Probation Act. That means even if it’s your first offence, the conviction goes on your record.

Can You Be Charged Under Another Section Instead?

Yes. The Act says that someone charged under Section 4 may instead be found guilty under Section 5 (drunk in charge) if appropriate. So, if there's doubt about whether you were driving, Gardaí might try to use that as a fallback.