What is the legal drink-drive limit in Northern Ireland?

The legal limit in Northern Ireland (as in England and Wales) is 80 mg of alcohol per 100 ml of blood, the blood alcohol concentration or BAC. Scotland uses a lower 50 mg limit. There is no reliable way to know how much you can drink and stay under the limit, so the safe rule is none for the road.

How does alcohol impair driving?

Alcohol is a depressant. It slows reaction times, impairs judgement of speed and distance, reduces co-ordination, blurs vision and a narrows the field of view, increases risk-taking through false confidence, and causes drowsiness.

What makes up the overall stopping distance?

Overall stopping distance is thinking distance plus braking distance. Thinking distance is how far you travel during your reaction time, and is increased by speed, alcohol, drugs, tiredness and distraction. Braking distance is how far you travel while braking, rises with the square of the speed, and is increased by wet or icy roads, worn tyres or brakes, a heavier load and going downhill.

Who are the most vulnerable road users?

Pedestrians (especially children, older and disabled people), cyclists, motorcyclists and horse riders. They have little or no protection in a crash and can be hard to see or unpredictable, so the Highway Code hierarchy puts extra responsibility on those who can do the most harm to protect them.

What are the three Es of road safety?

Engineering (safer roads and vehicles, such as roundabouts, crash barriers, seat belts and airbags), Enforcement (the law and policing, such as speed cameras, breathalysers and penalty points) and Education (informing and training road users, such as the Highway Code, the driving test and safety campaigns). Together they cut casualties more than any one alone.

Northern IrelandMotor Vehicle & Road User Studies

Driver impairment and road safety - CCEA GCSE MVRUS study guide

A CCEA GCSE Motor Vehicle and Road User Studies study guide to driver impairment and road safety: alcohol and the legal limits, drugs and fatigue, speed and stopping distances, vulnerable road users, and the three Es of road safety.

Generated by Claude Opus 4.88 min readCCEAUpdated 2026-06-15

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this module covers
How the topics fit together
How it is assessed
How to revise this module

What this module covers

This module covers the human and safety side of CCEA GCSE Motor Vehicle and Road User Studies (MVRUS), examined in Unit 1: Motor Vehicle and Road Use Theory. It deals with the things that impair a driver - alcohol, drugs and fatigue - the danger of speed and how stopping distance is made up, the protection of vulnerable road users, and the three Es that drive road-safety policy.

How the topics fit together

Alcohol and the legal limits - how alcohol impairs driving, the 80 mg/100 ml BAC limit, and the penalties for drink-driving.
Drugs, fatigue and other impairments - illegal and medicinal drugs, tiredness, illness and distraction, and how to avoid each.
Speed and stopping distances - why speed is dangerous and the make-up of overall stopping distance as thinking plus braking distance.
Vulnerable road users and their safety - who is most at risk and the crossings, conspicuity and behaviour that protect them.
The three Es of road safety - Engineering, Enforcement and Education, and why they work best together.

How it is assessed

Unit 1 is a written paper. Expect to:

Explain the effects of alcohol, drugs and fatigue and how to avoid impairment.
State the BAC limit and the penalties for drink-driving.
Break down overall stopping distance and list factors affecting each part.
Identify vulnerable groups and describe pedestrian crossings.
Answer a longer three Es question with meanings and examples.

How to revise this module

Learn the BAC figure (80 mg/100 ml) and a short list of alcohol's effects.
Practise giving both effects and prevention for drugs and fatigue.
Memorise that thinking distance depends on reaction time and braking distance on the square of speed.
Learn the crossings and the driver's duty at each (give way at a zebra; flashing amber at a pelican).
Be ready to write the three Es with an example of each and explain why all three are needed.

Sources & how we know this

CCEA GCSE Motor Vehicle and Road User Studies specification — CCEA (2017)
The Highway Code (DfT/DOE NI) — Department for Transport (2022)