What is a preliminary breath test (PBT)?

A preliminary breath test (PBT) is specifically designed as a roadside test to estimate a driver's blood alcohol concentration (BAC). This test is typically administered by law enforcement officers during a traffic stop when they suspect a driver may be under the influence of alcohol. The primary purpose of the PBT is to provide a quick assessment of whether a driver has consumed alcohol and if their BAC exceeds legal limits, which helps officers make immediate decisions regarding further testing or potential arrest.

The PBT is a preliminary measure and not a definitive legal standard; it is used to gather evidence that may indicate impairment. The results of this test are generally not admissible in court as the primary evidence of BAC, but they can lead to further investigation or arrest.