Drinking and driving is dangerous! Some people think they know their own limits; however the reality is they do not. Sure you can touch your nose or walk in a straight line, but according to the law this is not really an indication of sobriety.
Blowing smoke into a keychain breathalyzer could also cause harm to the sensor. This could cause your machine to malfunction. It is important to read the directions and manuals that come with the device in order to get the longest possible life out of it.
Sobriety checkpoints are used to stop impaired drivers and deter people from drinking and driving. These checkpoints have been proven to reduce alcohol related crashes and deaths by twenty percent.
All drivers rely on speedometers to keep driving speed within the legal limits. What if cars came without speedometers and the police still enforced speeding laws with high tech radar guns? It would be very difficult to tell what a particular speed feels like if you never had your speed tested.