title: Restricted driver licensing for medical impairments: does it work?
abstract: BACKGROUND
  Medical conditions may adversely affect driving ability. Many North American jurisdictions provide restricted driving licences that permit people with certain medical conditions to drive under limited conditions, but the effectiveness of such programs has not yet been determined. The objectives of this study were to evaluate the rates of crashes and traffic violations among drivers with a restricted licence, compared with the rates in the general driving population, and to compare the crash and traffic violation rates before and after driving restrictions were imposed.
  
  
  METHODS
  We retrospectively analyzed a cohort of all licensed Saskatchewan drivers registered from Jan. 1, 1992, to Apr. 19, 1999. The cohort was divided into those with a restricted licence and those with an unrestricted general licence. We used multivariate Poisson regression to calculate incidence rate ratios (IRRs) for at-fault crashes and traffic violations, adjusting for age, sex and residence (urban v. rural). We used interventional time series analysis to compare rates of crashes and traffic violations before and after the imposition of driving restrictions.
  
  
  RESULTS
  Of the 703,758 drivers in the study, 23,185 (3.3%) had a restricted licence. Restricted licence holders had a higher crash rate than drivers without restrictions (adjusted IRR 1.13, 95% confidence interval [CI] 1.11-1.17). However, this rate was lower than that among male drivers (adjusted IRR 2.01, 95% CI 1.99-2.02) and urban drivers (adjusted IRR 1.38, 95% CI 1.37-1.39). Drivers with restricted licences had a lower traffic violation rate than those without restrictions (adjusted IRR 0.93, 95% CI 0.91-0.95). At-fault crash rates decreased by 12.8% (95% CI 2.4%-23.2%) and adjusted traffic violation rates decreased by 10.0% (95% CI 4.4%-15.7%) after restrictions were imposed. During the study period, licence restrictions likely averted up to 816 crashes and 751 traffic violations.
  
  
  CONCLUSIONS
  Province-wide population data suggest that a restricted licensing program appears to provide a significant decrease in the rates of crashes and traffic violations.
authors.affiliation: Department of Medicine, University of Ottawa, Ont. smarshall@ottawahospital.on.ca
authors.forename: Shawn C
authors.initials: SC
authors.lastname: Marshall
authors.forename: Robert
authors.initials: R
authors.lastname: Spasoff
authors.forename: Rama
authors.initials: R
authors.lastname: Nair
authors.forename: Carl
authors.initials: C
authors.lastname: van Walraven
mesh_terms: D000063:Accidents, Traffic / Q000517:prevention & control / Q000706:statistics & numerical data*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001334:Automobile Driving / Q000331:legislation & jurisprudence*; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008004:Licensure / Q000331:legislation & jurisprudence*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009656:North America; D012044:Regression Analysis; D012189:Retrospective Studies; D012525:Saskatchewan