Psychopharmacology (2012) 220:293–301 DOI 10.1007/s00213-011-2484-0 ORIGINAL INVESTIGATION Predicting psychopharmacological drug effects on actual driving performance (SDLP) from psychometric tests measuring driving-related skills Joris C. Verster & Thomas Roth Received: 25 May 2011 / Accepted: 31 August 2011 / Published online: 16 September 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Rationale There are various methods to examine driving ability. Comparisons between these methods and their rela- tionship with actual on-road driving is often not determined. Objective The objective of this study was to determine whether laboratory tests measuring driving-related skills could adequately predict on-the-road driving performance during normal traffic. Methods Ninety-six healthy volunteers performed a standard- ized on-the-road driving test. Subjects were instructed to drive with a constant speed and steady lateral position within the right traffic lane. Standard deviation of lateral position (SDLP), i.e., the weaving of the car, was determined. The subjects also performed a psychometric test battery including the DSST, Sternberg memory scanning test, a tracking test, and a divided attention test. Difference scores from placebo for parameters of the psychometric tests and SDLP were computed and correlated with each other. A stepwise linear regression analysis determined the predictive validity of the laboratory test battery to SDLP. Results Stepwise regression analyses revealed that the combination of five parameters, hard tracking, tracking and reaction time of the divided attention test, and reaction time and percentage of errors of the Sternberg memory scanning test, together had a predictive validity of 33.4%. J. C. Verster (*) Utrecht Institute for Pharmaceutical Sciences, Division of Pharmacology, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands e-mail: j.c.verster@uu.nl T. Roth Sleep Disorders and Research Center, Henry Ford Health System, Detroit, MI, USA Conclusion The psychometric tests in this test battery showed insufficient predictive validity to replace the on- the-road driving test during normal traffic. Keywords Driving . SDLP . Psychometric tests . Predictive validity Introduction The use of central nervous system (CNS) drugs such as anxiolytics and hypnotics may significantly increase the risk of having a traffic accident and related injury (Orriols et al. 2009). The main reason for the increased risk of traffic accidents is that the use of CNS drugs also can have adverse effects such as sedation and reduced alertness, which impair driving ability. Many tests are used to determine whether drugs may impair performance and to judge whether patients using these drugs are fit for driving. To determine whether a test is suitable to examine fitness for driving, it is important to take note of different models that describe driving behavior, in particular information processing and motivational models. Motivational models focus on the risks drivers are willing to take during driving (Wilde 1982; Näätänen and Summala 1976; Fuller 1984) and state that driving behavior is determined by a conscious cost–benefit analysis between the motives and goals of the trip and safety risks (Ranney 1994). Drivers adapt their driving behavior to their personal or environmental needs. For example, drivers generally adjust their speed under bad weather conditions but take high risks by speeding in case of an emergency. In contrast to motivational models, information processing models analyze driving skills and abilities at a functional level.