Abstract
The police officer is limited by four factors in his ability to make alcohol related driving arrests: traffic density, percent of drivers with B.A.C.'s of 100 mg% or higher, his ability to identify impairment as drivers pass his station, and the degree of support he receives from prosecutors, judges and his own superiors in the police department. Major emphasis in measuring effects of increased enforcement, therefore, must be placed upon achievement of deterrence rather than on whether an increase in the number of arrests has occurred.