Samenvatting
Prior to arresting a driver on suspicion of alcohol intoxication, a police officer needs good reason to believe that such an arrest is justifiable. He is then often forced to rely on his own judgement, and often looks for gross signs of impairment. This paper presents part of the results of a field study which investigated the quality of police officers' unaided decisions for requiring a roadside breath test in a (semi) natural setting.