title: Challenges associated with drunk driving measurement: combining police and self-reported data to estimate an accurate prevalence in Brazil.
abstract: BACKGROUND
  Drunk driving is an important risk factor for road traffic crashes, injuries and deaths. After June 2008, all drivers in Brazil were subject to a "Zero Tolerance Law" with a set breath alcohol concentration of 0.1 mg/L of air. However, a loophole in this law enabled drivers to refuse breath or blood alcohol testing as it may self-incriminate. The reported prevalence of drunk driving is therefore likely a gross underestimate in many cities.
  
  
  OBJECTIVE
  To compare the prevalence of drunk driving gathered from police reports to the prevalence gathered from self-reported questionnaires administered at police sobriety roadblocks in two Brazilian capital cities, and to estimate a more accurate prevalence of drunk driving utilizing three correction techniques based upon information from those questionnaires.
  
  
  METHODS
  In August 2011 and January-February 2012, researchers from the Centre for Drug and Alcohol Research at the Universidade Federal do Rio Grande do Sul administered a roadside interview on drunk driving practices to 805 voluntary participants in the Brazilian capital cities of Palmas and Teresina. Three techniques which include measures such as the number of persons reporting alcohol consumption in the last six hours but who had refused breath testing were used to estimate the prevalence of drunk driving.
  
  
  RESULTS
  The prevalence of persons testing positive for alcohol on their breath was 8.8% and 5.0% in Palmas and Teresina respectively. Utilizing a correction technique we calculated that a more accurate prevalence in these sites may be as high as 28.2% and 28.7%. In both cities, about 60% of drivers who self-reported having drank within six hours of being stopped by the police either refused to perform breathalyser testing; fled the sobriety roadblock; or were not offered the test, compared to about 30% of drivers that said they had not been drinking.
  
  
  CONCLUSIONS
  Despite the reduction of the legal limit for drunk driving stipulated by the "Zero Tolerance Law," loopholes in the legislation permit many drivers under the influence of alcohol to act with impunity. In this context the police/traffic officers are often powerless to enforce the law and thus drunk driving continues to go unchecked.
  
  
  CONCLUSIONS
  Strong legislation and effective enforcement are necessary to reduce the prevalence of this dangerous behaviour. Correction techniques allow calculation of a truer prevalence of drunk driving, which can assist police and policymakers alike to redirect resources and align strategies.
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil. Electronic address: trsousa@hcpa.ufrgs.br.
authors.forename: Tanara
authors.initials: T
authors.lastname: Sousa
authors.affiliation: Johns Hopkins International Injury Research Unit, Johns Hopkins Bloomberg School of Public Health, USA.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Lunnen
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Veralice
authors.initials: V
authors.lastname: Gonçalves
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Aurinez
authors.initials: A
authors.lastname: Schmitz
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Graciela
authors.initials: G
authors.lastname: Pasa
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Tamires
authors.initials: T
authors.lastname: Bastos
authors.affiliation: Johns Hopkins International Injury Research Unit, Johns Hopkins Bloomberg School of Public Health, USA.
authors.forename: Pooja
authors.initials: P
authors.lastname: Sripad
authors.affiliation: Johns Hopkins International Injury Research Unit, Johns Hopkins Bloomberg School of Public Health, USA.
authors.forename: Aruna
authors.initials: A
authors.lastname: Chandran
authors.affiliation: Center for Drug and Alcohol Research, Federal University of Rio Grande do Sul, Brazil.
authors.forename: Flavio
authors.initials: F
authors.lastname: Pechansky
mesh_terms: D000063:Accidents, Traffic / Q000331:legislation & jurisprudence* / Q000517:prevention & control / Q000523:psychology; D000328:Adult; D000428:Alcohol Drinking / Q000097:blood / Q000453:epidemiology / Q000331:legislation & jurisprudence*; D001334:Automobile Driving / Q000193:education / Q000331:legislation & jurisprudence* / Q000523:psychology; D001938:Brazil / Q000453:epidemiology; D001944:Breath Tests; D004522:Educational Status; D005260:Female; D006801:Humans; D035846:Law Enforcement / Q000379:methods; D008297:Male; D016495:Police; D011050:Policy Making; D015995:Prevalence; D036301:Qualitative Research; D012307:Risk Factors; D057566:Self Report; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires
keywords: Alcohol; Brazil; Drink Driving; Enforcement; Latin America; Legislation; Policy; Risk Factor; Road Safety; Road Traffic Injuries