Psychopharmacology (2012) 220:293–301 understand and judge whether a CNS drug is safe when it comes to driving or to determine whether a patient is fit for driving. Researchers have combined various psychometric tests and claimed that their test battery predicts actual driving (Fitten et al. 1995; Marottoli et al. 1998; McKnight and McKnight 1999; De Raedt and Pontjaert-Kristoffersen 2001). Their conclusion is often based on the fact that they find a significant relationship between performance on cognitive and psychomotor tests and driving performance, showing a predictive validity up to 85%. In these studies, driving performance was either judged subjectively by a driving instructor or researcher, or driving performance was measured using a driving simulator. Other researchers, however, reported that their tests had no significant predictive validity (Galski et al. 1990; Korteling and Kaptein 1996; Duchek et al. 1998; Bliokas et al. 2011; Devos et al. 2011). The tests that were included in these studies vary greatly. An explanation for differences in the relationship between impairment on cognitive or psycho- motor tests versus actual driving impairment is that these tests all have a different sensitivity for drug-induced impairment. This was shown by Moskowitz and Fiorentino (2000) who summarized data on several tests and deter- mined at which blood alcohol concentration (BAC) significant impairment was demonstrated by the majority of reviewed studies. Moskowitz and Fiorentino (2000) reported that BAC levels ranged from 0.1% to 1.0%, depending on the test that was chosen (see Fig. 2). A study by Myers et al. (2000) illustrates that the choice of tests is of great importance. In their study, a laboratory test battery comprising visual screening, a reaction time task, a split-attention task, a visual organization test, and a verbal and symbolic sign recognition test did not adequately predict on-road driving performance of patients referred for evaluation of their driving skills. However, applying the Useful Field Of View test (UFOV, a three-part test, measuring speed of visual processing, ability to divide attention, and selective attention) a predictive validity of 86% was found. Fig. 2 Blood alcohol concentration (BAC) at which more than half of tests showed significant impairment (Moskowitz and Fiorentino 2000) 295 Two major limitations of the methodology to assess actual driving performance prevent a fair judgment of the test batteries used in the studies discussed above. First, subjective assessments of driving performance often lack standardiza- tion, and reliability and validity are not determined (Fox et al. 1998). Also, simple ratings of driving performance (e.g., visual analog scales or passing/failing judgments) do not sufficiently differentiate between performance levels. A recent comparison also showed that drivers themselves also poorly predict their own driving performance (Verster and Roth 2011a). Second, it can also be questioned if assess- ments in a driving simulator can adequately predict actual driving. Although today, very advanced driving simulators are available, it remains a test in an artificial environment, the test may be experienced as a game, and in contrast to on- road driving the test poses no real safety risks. Therefore, it is likely that motivation to perform a driving simulator test is different from on-road driving (Verster and Roth 2011a). As stated by O'Hanlon (1988), a realistic driving test is needed to assess the safe use of drugs by drivers. In their effort to mimic actual driving circumstances, researchers also used closed roads to test driving performance (e.g., Betts and Birtle 1982). Closed road tests often comprise testing specific driving behaviors, such as maneuvering the vehicle along a circuit of cones, gap judgment, parking, or measuring break reaction time (e.g., Tashiro et al. 2005). Although it may be interesting to examine what happens in these special circumstances, the obtained data provides little information on how drivers will behave in normal traffic. Another major disadvantage of this approach is that other traffic is not present during the test. Since interacting with other drivers is an essential element of participating in traffic, this greatly limits the ecological validity of these tests. Taken together, the subjective nature of the on-road assessments, the use of driving simulator assessments, and the questionable relevance to driving of some of the included tests, probably accounts for the inconclusive results of studies that aimed at developing a suitable test battery to replace actual driving tests. Currently, the on-the-road driving test in normal traffic is regarded as the gold standard to examine driving ability (O'Hanlon et al. 1982; Verster and Roth 2011b). This 100-km driving test is performed on a public highway in normal traffic. Participants are instructed to drive with a steady lateral position within the right traffic lane and a constant speed (95 km/h). The primary outcome measure is the Standard Deviation of Lateral Position (SDLP), i.e., the weaving of the car. A disadvantage of the test is that it is time consuming and relatively expensive and requires an instru- mented vehicle and trained personnel. Therefore, it would be more efficient to have an easy to use psychometric test battery that could predict actual driving. Cognitive and psychomotor tests can provide valuable information about specific impair-