Ignition interlock deviceSwitzerland

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278. Ignition interlock device

An ignition interlock device, also called an alcohol interlock or alcolock, is a breath-testing device connected to a vehicle’s ignition system. Before the vehicle can be started, the driver must provide a breath sample below a programmed alcohol limit. The device may also require additional tests during a journey and can record information about tests, failed attempts and possible tampering. Ignition interlocks are used in some countries as a safety measure or legal requirement for drivers convicted of alcohol-related offences.

Ignition interlock device
Ignition interlock device installed in a Scania Postbus coach.
Wikimedia.org • Spielvogel • CC0
What is an ignition interlock device?

An ignition interlock device is a breath-testing system connected to a vehicle that prevents the engine from starting when the driver’s alcohol concentration exceeds the programmed limit.

How does an ignition interlock work?

Before starting the vehicle, the driver provides a breath sample. If the alcohol concentration is below the permitted threshold, the vehicle can be started.

Can an ignition interlock require another test while driving?

Some systems require additional breath tests during a journey to confirm that the authorised driver remains compliant. The exact procedure depends on the device and applicable rules.

Does an ignition interlock record information?

Yes. Many systems can record breath-test results, failed attempts, events and possible attempts to interfere with the device.

Who may be required to use an ignition interlock?

Depending on the country, an ignition interlock may be required for drivers convicted of serious or repeated alcohol-related driving offences.

Can another person blow into an ignition interlock for the driver?

No. Having another person provide the breath sample defeats the purpose of the system and may be treated as tampering or non-compliance under the applicable rules.

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