Accident Analysis and Prevention 31 (1999) 631 – 638 Predictors of safety belt use among crash-involved drivers and front seat passengers: adjusting for over-reporting Lei Li a, *, Karl Kim b , Lawrence Nitz c a Accident Research Center, Monash Uniersity, BLD 70, Wellington Road, Clayton, VIC 3168, Australia b Department of Urban and Regional Planning, Porteus Hall, 2424 Maile Way, Uniersity of Hawaii at Manoa, Honolulu, HI 96822, USA c Department of Political Sciences, Porteus Hall, 2424 Maile Way, Uniersity of Hawaii at Manoa, Honolulu, HI 96822, USA Received 29 June 1998; received in revised form 23 November 1999 Abstract Police-reported crash data are rarely used to investigate safety belt use and its predictors, even though these data have a number of advantages over data collected in roadside surveys. It has been widely recognized that motorists tend to over-report their safety belt use to police when mandatory belt use becomes law. In this paper, we use a logistic regression model that allows for misclassification errors in outcome variable to examine predictors of safety belt use among crash-involved drivers and front seat passengers. Our analysis shows significant associations between occupant characteristics, driving circumstances, and safety belt use. Alcohol involvement has the strongest negative association with safety belt use, but this association would be considerably underestimated without adjusting for the over-reporting of safety belt use in police-reported crash data. The adjusted belt use rate among front seat occupants with at least nonincapacitating injuries is about 81%, compared to 90% in police-reported crash data. © 1999 Elsevier Science Ltd. All rights reserved. Keywords: Police-reported data; Safety belt use; Over-reporting; Logistic regression; Specificity www.elsevier.com/locate/aap 1. Introduction While it is a truism that ‘safety belts save lives’ and most states have mandatory safety belt use laws in the United States, many people still do not use safety belts. It had been projected that safety belts saved about 4573 lives in 1988 when the use rate was 45% and could have saved about 11 101 lives if the use rate was 80% in the United States (Partyka and Womble, 1989). As of December 1995, the belt use rate varied with states from 40 to 86% with a national average estimated at 68% (National Highway Traffic Safety Administration, 1996). Hawaii has consistently had a use rate above 80% and currently is ranked the sixth highest of all states with data available. Primary enforcement which allows police to stop vehicles for failure to wear a safety belt is believed to have been an important factor in achieving a high use rate (Kim, 1991; Escobedo et al., 1992). There have been many studies estimating safety belt use rates or identifying motorists most likely to be in compliance with mandatory safety belt use laws. These studies typically use specifically designed data collection procedures, involving roadside observational surveys and posterior interviews with vehicle owners identified by license plates or other means. Police-reported crash data are generally not used because of concerns with the accuracy of police-reported safety belt use (Streff and Wagenaar, 1989; O’Day, 1993; Stewart, 1993; Re- infurt et al., 1996). Because of mandatory belt use laws, and the associated fines and other sanctions, motorists have incentives to be less than truthful to law enforce- ment officials. Stewart (1993) found that among drivers observed in a survey who classified themselves as ‘rarely or never belted’, about 80% were recorded as belted in the police crash reports. In our own analysis using Hawaii data, we have found that among patients admit- ted to hospitals following motor vehicle crashes, about 25% of those who reported to police that they were belted, reported to doctors or medical personnel that they were unbelted. Blincoe (1994) reported that the * Corresponding author. Tel.: +61-3-99051814; fax: +61-3- 99051809. E-mail address: lei.li@general.monash.edu.au (L. Li) 0001-4575/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII:S0001-4575(99)00022-6