Drivers of the country's National Express fleet of luxury buses are required to blow into the device before they can start the engine.
Any trace of alcohol immobilises the vehicle and sends out information to a control centre, the Daily Express reported.
A driver who is found drunk would have to appear before a disciplinary hearing and, if proven, may even be sacked.
So far, 480 coaches have been fitted with the device and the entire 600-strong fleet would reportedly be equipped by September this year.
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