These questions test three decisions: whether the driving prohibition applies, which measurement rule is engaged, and what the driver must do during a lawful procedure. Keep the alcohol and drug routes distinct while remembering that neither route depends on a crash.
Follow the rule from driving to measurement
Start with the activity and condition. The intoxicated-driving prohibition reaches motor vehicles, trams and bicycles. For alcohol, the statutory prohibited threshold begins at 0.03 percent blood-alcohol concentration. Do not replace that current threshold with an older figure from a summary. For drugs and other causes, the broader safety question is whether drugs, overwork, illness or another cause creates a risk that the person cannot drive normally. The safest decision is made before movement: do not drive when that condition exists.
| Stage | Rule to apply |
|---|---|
| Alcohol threshold | Use the current 0.03 percent BAC boundary. |
| Required breath test | Traffic-safety need or reasonable suspicion can support the requirement, and the driver complies. |
| Disputed breath result | With consent, use blood collection or another recognized method within the procedure. |
| Measurement integrity after driving | Ask whether later conduct was intended to distort measurement of the earlier alcohol level; that purpose controls the prohibition. |
| Suspected drug impairment | Apply the testing power in force on or after 2 April 2026 when reasonable suspicion exists. |
The drug-testing date is a boundary, not background detail. On or after 2 April 2026, police who have reasonable grounds to suspect drug-impaired driving may require a saliva reagent test or another prescribed test, and the driver must comply. That does not create a free-standing test for every driver in every situation; the stated reasonable-suspicion condition remains part of the rule. Alcohol retesting has a different structure. A driver disputing a completed breath result may be retested by blood collection or another method when the driver consents. A later private result disconnected from that procedure does not become the recognized retest merely because it is newer.
The traps
- Substituting a disconnected private test several days later for the recognized retest procedure. A challenge to the roadside result stays within the prescribed process.
- Assuming a disputed breath result can never be checked again. With the driver's consent, blood collection or another recognized method can be used.
- Making a crash a prerequisite for a required breath test. Traffic-safety need or reasonable suspicion can support the requirement without a collision.
- Making a crash a prerequisite for a required drug test. On or after 2 April 2026, reasonable suspicion can support the prescribed procedure without a collision.
Try it
Under the current national rule, at what blood-alcohol concentration does the statutory prohibited threshold begin? Enter the number as a percent BAC.
After driving, a suspected driver drinks more alcohol specifically to disrupt measurement of the earlier alcohol level. How does the national rule treat that conduct?
- It is permitted once the car is parked, even when the purpose is to confuse the measurement
- It is prohibited when intended to obstruct measurement
- It is required before any second test
- It is allowed if done at home