These are actually two separate criminal charges. The legal limit of driving with alcohol in your system is 80 mgs in 100 mL of blood. However, even if you have a lower blood alcohol level, you can still be charged with impaired driving if the police officer believes that your ability to drive the motor vehicle was impaired by alcohol. As well, even if you don’t show any signs of impairment, you can still be charged with over 80 if your blood alcohol level exceeds this amount. The consequences of being convicted of either of these offences are essentially the same.