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Preliminary tests (breath, impairment and drug tests)

ss.6–6CRoad Traffic Act 1988

Lets a constable require a driver or person in charge of a motor vehicle to co-operate with a roadside breath, impairment or drug test, where drink or drugs, a moving traffic offence or an accident is suspected.

Preliminary tests (breath, impairment and drug tests) · Road Traffic Act 1988, ss.6–6CCard 42 / 59

When you can use it

The person is or was driving, attempting to drive or in charge of a motor vehicle on a road or other public place
s.6(2)Reasonable suspicion that the person is doing so and has alcohol or a drug in their body, or is under the influence of a drug
s.6(3)Reasonable suspicion that the person has done so with alcohol or a drug in their body (or while unfit to drive through a drug), and still has alcohol or a drug in their body or is still under the influence of a drug
s.6(4)Reasonable suspicion that the person is or has been doing so and committed a traffic offence while the vehicle was in motion
s.6(5)An accident occurred owing to the presence of a motor vehicle on a road or public place, and the constable reasonably believes the person was driving, attempting to drive or in charge at the time
s.6(7)For s.6(2)–(4), the constable must be in uniform; s.6(5) has no uniform requirement

What it allows

Requiring the person to co-operate with one or more preliminary tests, given by the requiring constable or another constable.
Breath test (s.6A) – under s.6(2)–(4), at or near the place of the requirement. After an accident (s.6(5)), it may instead be at a police station the constable specifies.
Impairment test (s.6B) and drug test (s.6C) – at or near the place of the requirement, or at a police station the constable specifies if they think it expedient.
Entry to any place, by reasonable force if necessary, to require a test or arrest after an accident where injury is reasonably suspected (s.6E).

Key definitions

Preliminary breath test – s.6A: a breath sample is used by an approved device to indicate whether alcohol is likely to be over the prescribed limit.
Preliminary impairment test – s.6B: the constable observes the person doing set tasks and their physical condition, to indicate unfitness to drive and whether drink or drugs is the likely cause.
Preliminary drug test – s.6C: a sweat or saliva sample is analysed by an approved device to indicate whether a drug is present and, if so, whether it is a specified controlled drug likely to be over its limit.
Traffic offence – s.6(8): an offence under listed road traffic Acts, including most of the 1988 Act.

Safeguards

Only a constable approved by their chief officer may give an impairment test, and they must have regard to the Secretary of State’s code of practice (s.6B(5)–(6)).
No more than three preliminary drug tests may be given (s.6C(3)).
Hospital patients – the doctor in immediate charge must be told first and may object on grounds of the patient’s care. Any test must be at the hospital (s.9). A patient at hospital cannot be arrested under s.6D(3).

Good to know

Failing without reasonable excuse to co-operate is an offence (s.6(6)).
Arrest (s.6D) – without warrant where a test gives reasonable suspicion of being over the limit, or on failure to co-operate with reasonable suspicion of alcohol or drugs. Once arrested, the person may be kept at or near the scene for s.7 evidential tests instead of going to a station (s.6D(2A)).
Exam trap: a vehicle can be stopped at random under s.163, but suspicion (or an accident) must exist before a test is required.

Legislation: Road Traffic Act 1988, ss.6–6C (opens legislation.gov.uk in a new tab)
Who can use it: A constable (in uniform for s.6(2)–(4))
Last checked: 3 November 2026, against the current law on legislation.gov.uk

Preliminary tests (breath, impairment and drug tests): questions people ask

When can the police use preliminary tests (breath, impairment and drug tests)?

1. The person is or was driving, attempting to drive or in charge of a motor vehicle on a road or other public place 2. Reasonable suspicion that the person is doing so and has alcohol or a drug in their body, or is under the influence of a drug 3. Reasonable suspicion that the person has done so with alcohol or a drug in their body (or while unfit to drive through a drug), and still has alcohol or a drug in their body or is still under the influence of a drug 4. Reasonable suspicion that the person is or has been doing so and committed a traffic offence while the vehicle was in motion 5. An accident occurred owing to the presence of a motor vehicle on a road or public place, and the constable reasonably believes the person was driving, attempting to drive or in charge at the time 6. For s.6(2)–(4), the constable must be in uniform; s.6(5) has no uniform requirement

Who can use preliminary tests (breath, impairment and drug tests)?

A constable (in uniform for s.6(2)–(4))

What law gives the power for preliminary tests (breath, impairment and drug tests)?

Road Traffic Act 1988, ss.6–6C.

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