Driving under the influence charges in Pennsylvania are more serious than most people realize. It is illegal to operate a motor vehicle with a blood alcohol content of 0.08 percent or higher. It is also illegal to operate a vehicle with any detectable amount of a controlled substance or its metabolites in your blood, even if you are not visibly impaired. A controlled substance DUI or a refusal to submit to testing falls under the highest tier and carries the most severe penalties. Prior offenses