Consuming alcohol can be a nice way to relieve stress, or to simply allow a person to let loose a little bit for an evening. In moderation, generally, there is nothing wrong with doing this. However, while alcohol can be a good way to let loose, it also can impair one's ability to perform certain tasks. One of these is driving a vehicle. Due to the harm impaired drivers can cause, drinking and driving is illegal, and the penalties for engaging in it can be very harsh.
For people driving their personal vehicles, the legal limit for blood alcohol concentration (BAC) is .08 and the penalties increase as the BAC increases. However, for those who drive commercial vehicles for a living and transport people for governments, contractors or schools, the standard is higher. If a person is driving a commercial vehicle, he or she is considered intoxicated if the BAC is above .04. It is even a higher standard if the person is driving a school vehicle. The person driving a school vehicle must have a BAC below .02.
If the person's BAC is higher than that, then he or she could be charged with a DUI. If that occurs, the individual will then potentially face the harsh consequences associated with a DUI, including license suspension, which could make it impossible to continue a job as a driver. People who are charged are still innocent until proven guilty, though and there may be defenses available to them.
Many people in Philadelphia drive vehicles for a living. Since they drive professionally and, in some cases, transport children as a part of their jobs, the law says that their BAC must be lower than that of an individual driving a personal vehicle. The penalties can be very harsh, but there are potential defenses which are important to understand in order to protect one's rights.
Source: Pennsylvania State Legislature, "Pennsylvania Statute 3802(f)" accessed on Nov. 14, 2016