A method and apparatus for detecting impairment of a vehicle operator are provided. The method includes detecting a first impairment level at a first time; detecting a second impairment level at a second time after the first time; based on the detected first impairment level and the detected second impairment level, determining a third impairment level at a third time after the second time; and inhibiting vehicle operation in response to determining that the third impairment level is greater than an impairment threshold. The apparatus and method may be used in a vehicle or other apparatus to prevent vehicle operator from operating the vehicle while impaired or prior to becoming impaired.