In Pennsylvania, you submit to the form of the test chosen by the police officer, usually a breath, blood or urine. Analysis of a blood sample is potentially the most accurate, as will be discussed in other videos. Breath machines are susceptible to a number of problems, rendering them often unreliable. The least accurate by far, however, is urinalysis. Thus, if you are offered a choice of tests and you are confident that you are sober, a blood sample is the wise choice. Urine being the least accurate and most easily impeached is the best option if you believe your blood alcohol concentration is above the legal limit.