294 Like many behaviors, driving a car is a mix of automatic and controlled behaviors [Schneider and Shiffrin 1977; Shiffrin and Schneider 1977). Rasmussen (1987) explains driving behavior distinguishing three levels of cognitive control: skill-based, rule-based, and knowledge-based be- havior (see Fig. 1). Skill-based behavior comprises automatic and effortless routine driving (e.g., changing gear). In contrast, rule-based and knowledge-based behaviors are controlled actions to deal with changing driving circum- stances. Rule-based behavior follows prescribed rules (e.g., passing a slower vehicle). With increased driving experience, and if the rules show to be effective, rule-based behavior becomes automatic (skill-based) behavior. If rule-based behavior is not effective, conscious problem solving (knowl- edge-based behavior) is necessary to master the new situation. When the driver becomes familiar with the new driving situation, behavior starts following rules (rule-based behavior) or may become more or less automatic (skill-based level). A similar model by Michon (1985) explained driving at the strategic (navigation), maneuvering (tactical), and operational level. Performance at the strategic level is predominantly memory-driven, controlled processing, and concerns trip-planning and achievement of goals. Perfor- mance at the maneuvering level is environmental/data- driven, controlled processing, and includes normal driving procedures such as passing other cars or reacting to other traffic. At the operational level, behavior is automatic and concerns immediate vehicle control, such as changing gear. Decisions made at the strategic level take minutes, those made the maneuvering level are made within seconds, and at the operational level, decisions are made within 1 s. The relationship between the models of Rasmussen and Michon is shown in Fig. 1. Thus, depending on the relationship between uncertainly and experience of the driver, driving behaviors can switch Psychopharmacology (2012) 220:293–301 between the three levels of driving behavior and comprise automatic (fast and effortless) or controlled processing (slow and effortful). Various methodologies are applied to determine whether or not a patient is fit for driving when using a CNS drug, ranging from subjective assessments by driving instructors and psychometric testing to driving simulator tests or actual driving tests on public highways. Cognitive and psychomotor tests are often used to assess driving-related skills and abilities. Generally, no complex equipment is required, and the tests are easy to conduct, relatively cheap, and testing can be done under controlled standardized conditions. Tests are often of short duration, and a variety of skills and abilities can be examined. This makes their use cost-effective and time-efficient. Of vital importance is that the tests measure a valid psychological construct (Parrott 1991a, b, c), are sensitive to the effects of CNS drugs (Hindmarch 1980), and have a clear relationship with driving. Unfortunately, this often is not the case. For example, finger tapping and the Critical Flicker Fusion Test (CFFT) are often included in test batteries, although their relationship to driving or any other real-life task is unclear. The presumed rationale for including these tests is that they are used in other research and showed to be sensitive to drug-induced impairment. Guidelines and recommenda- tions on the methodology and tests to determine driving ability have been published on behalf of the International Council on Alcohol, Drugs and Traffic Safety (ICADTS) (Vermeeren et al. 1993; Tailloires Report 2007; Walsh et al. 2008). There is consensus that tests should be (1) standardized, (2) valid and reliable, (3) be able to differentiate between dose-dependent drug effects, and (4) provide information on skills and abilities that are important during driving such as attention, alertness, vigilance, and psychomotor performance. These tests should cover perfor- mance on all levels of driving behavior in order to fully Fig. 1 A model of driving behavior according to Rasmussen and Michon. Experienced drivers operate at the gray-scaled diagonal of Fig. 2, whereas novice drivers operate in the upper right corner of the figure