Serving one group in the community (those motorists obeying the law) may justify unmarked units to catch those motorists disobeying the law (safety). Most would admit that the safety gains from marked units is of a brief duration while within sight of the marked unit. Once out of sight, motorists disobeying the law will go right back to disobeying the law. The fines and penalties associated with unmarked police cars working traffic serves as a punishment for those who police would otherwise not catch with a marked unit.

It is a political decision made by each jurisdiction. For those who believe strongly about prohibiting use of unmarked units should contact their elected representatives and lobby for legislation to that effect. If you are successful you may expect a backlash by numerous citizens who will lobby for safer roads by increased use of unmarked units.