I agree that breathalyser tests would help reduce traffic accidents, especially fatal ones, but they are only a small part of what needs to be done.
We should first ensure that outdated motoring laws should be scrapped and that all road signs are in place (and appropriately sited – currently many are confusing).
We should then strictly and unfailingly enforce our motoring laws to all. This would surely help remove some awful driving practices, like ignoring pedestrian crossings and hogging the overtaking lane, from our roads.