title: Excursions out-of-lane versus standard deviation of lateral position as outcome measure of the on-the-road driving test.
abstract: BACKGROUND
  The traditional outcome measure of the Dutch on-the-road driving test is the standard deviation of lateral position (SDLP), the weaving of the car. This paper explores whether excursions out-of-lane are a suitable additional outcome measure to index driving impairment.
  
  
  METHODS
  A literature search was conducted to search for driving tests that used both SDLP and excursions out-of-lane as outcome measures. The analyses were limited to studies examining hypnotic drugs because several of these drugs have been shown to produce next-morning sedation.
  
  
  RESULTS
  Standard deviation of lateral position was more sensitive in demonstrating driving impairment. In fact, solely relying on excursions out-of-lane as outcome measure incorrectly classifies approximately half of impaired drives as unimpaired. The frequency of excursions out-of-lane is determined by the mean lateral position within the right traffic lane. Defining driving impairment as having a ΔSDLP > 2.4 cm, half of the impaired driving tests (51.2%, 43/84) failed to produce excursions out-of-lane. Alternatively, 20.9% of driving tests with ΔSDLP < 2.4 cm (27/129) had at least one excursion out-of-lane.
  
  
  CONCLUSIONS
  Excursions out-of-lane are neither a suitable measure to demonstrate driving impairment nor is this measure sufficiently sensitive to differentiate adequately between differences in magnitude of driving impairment.
authors.affiliation: Utrecht Institute for Pharmaceutical Sciences, Division of Pharmacology, Utrecht University, Utrecht, The Netherlands; Centre for Human Psychopharmacology, Swinburne University, Melbourne, Australia.
authors.forename: Joris C
authors.initials: JC
authors.lastname: Verster
authors.forename: Thomas
authors.initials: T
authors.lastname: Roth
mesh_terms: D001334:Automobile Driving; D006801:Humans; D006993:Hypnotics and Sedatives / Q000009:adverse effects; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000187:drug effects
chemical_list: D006993:Hypnotics and Sedatives
keywords: SDLP; driving; excursions out-of-lane; impairment; on-road