Physicians have long recognized that different types of drugs affect people differently. Nonetheless, drugs may be categorized or classified according to certain shared symptomatologies or effects. The DRE categorization process is premised on these long-standing, medically accepted facts. DREs classify drugs in one of seven categories: Central Nervous System (CNS) Depressants, CNS Stimulants, Hallucinogens, Phencyclidine (PCP) and its analogs, Narcotic Analgesics, Inhalants, and Cannabis. Drugs from each of these categories can affect a person's central nervous system an impair a person's normal faculties, including a person's ability to safely operate a motor vehicle.