Trends and patterns in fatal US motorcycle crashes, 2000-2016.

Objective: To investigate trends of motorcyclist fatalities and identify at-risk populations by motorcyclist demographics and crash characteristics. Methods: We used the Fatality Analysis Reporting System (FARS) database (2000-2016) to track fatality rate trends, which were quantified by using Poisson mixed-effects regression models comparing 2000-2001 and 2007-2008, as well as 2009-2010 and 2015-2016. Results: The overall fatality rate per 100,000 population increased from 2000 to 2016, defined by two trend lines-before and after the economic recession in 2008-2009. The overall fatality rate ratio between 2000-2001 and 2007-2008 was 1.60 [95% Confidence Interval (CI): 1.51-1.70], and between 2009-2010 and 2015-2016 was 1.09 (95% CI: 1.02-1.18). Fatality rates increased among all age groups, particularly for motorcyclists aged 60 and older. Those aged 18-29 had the highest fatality rates overall. Age-and-sex standardized state fatality rates were consistently highest in Wyoming, South Dakota, and South Carolina and lowest in Massachusetts, New York and New Jersey. Conclusion: Motorcycle fatality rates increased overall and across all age groups between 2000 and 2016. Fatalities for the oldest riders showed the steadiest increasing trends. Results highlight the continued public health burden of motorcyclist fatalities and, by extension, the importance of improving motorcycle safety.

A cross-sectional study of travel patterns of older adults in the USA during 2015: implications for mobility and traffic safety.

BACKGROUND: With an ever increasing population of older adults (65+ years) in the USA, a better understanding of this population's travel patterns is needed to improve travel mobility and transportation safety. OBJECTIVE: In this study, we described the travel patterns of older adults in the USA during 2015. METHODS: Travel patterns of older adults (65-74 and 75+ years) were compared with younger adults (25-64 years) by frequency and proportion of daily trips. The daily trips of various age groups were estimated using the 2015 American Time Use Survey. RESULTS: The percentage of daily travellers was 88% for adults (25-64 years), 75% for adults (65-74 years) and 68% for adults (75+ years). While the percentage of privately owned vehicle (POV) drivers and average time of driving POVs decreased, the percentage of POV passengers increased as adults aged. Females were less likely to drive POVs and had decreased average daily driving time, but they were more likely to ride in POVs as passengers and had longer average daily riding times than their male counterparts across all age groups. Older adults were more likely to travel in the mornings and early afternoons (from 8:00 to 15:59) while younger adults were more likely to travel in the late afternoons and early evenings (from 16:00 to 19:59). CONCLUSIONS: POV use is the predominant mode of transit in the USA. As adults age, the percentages of daily travellers and POV drivers decrease. This pattern is more apparent among females than males. This study delineated travel patterns of older adults using a 2015 national survey, and the findings facilitate traffic systems designers and policy-makers to develop and implement initiatives to accommodate older adults' mobility needs and improve traffic safety.

Novelty helmet use and motorcycle rider fatality.

OBJECTIVES: To compare the risk of fatal injury across helmet types among collision-involved motorcyclists. METHODS: We used data from a cohort of motorcyclists involved in police-reported traffic collisions. Eighty-four law enforcement agencies in California collected detailed information on helmet and rider characteristics during collision investigations in June 2012 through July 2013. Multiply-adjusted risk ratios were estimated with log-binomial regression. RESULTS: The adjusted fatal injury risk ratio for novelty helmets was 1.95 (95% CI 1.11-3.40, p 0.019), comparing novelty helmets with full-face helmets. The risk ratios for modular, open-face, and half-helmets, compared with full-face helmets, were not significant. CONCLUSIONS: A more complete understanding of the inadequacy of novelty helmets can be used in educational and law enforcement countermeasures to improve helmet use among motorcycling populations in California and other US states. Law enforcement approaches to mitigating novelty helmet use would seem attractive given that novelty helmets can be visually identified by law enforcement officers with sufficient training.

Interferon Lambda 4 Genotype Is Associated With Jaundice and Elevated Aminotransferase Levels During Acute Hepatitis C Virus Infection: Findings From the InC3 Collaborative.

Symptomatic acute HCV infection and interferon lambda 4 (IFNL4) genotypes are important predictors of spontaneous viral clearance. Using data from a multicohort database (Injecting Cohorts [InC3] Collaborative), we establish an independent association between host IFNL4 genotype and symptoms of acute hepatitis C virus infection. This association potentially explains the higher spontaneous clearance observed in some patients with symptomatic disease.

Motorcycle helmet use and the risk of head, neck, and fatal injury: Revisiting the Hurt Study.

Most studies find strong evidence that motorcycle helmets protect against injury, but a small number of controversial studies have reported a positive association between helmet use and neck injury. The most commonly cited paper is that of Goldstein (1986). Goldstein obtained and reanalyzed data from the Hurt Study, a prospective, on-scene investigation of 900 motorcycle collisions in the city of Los Angeles. The Goldstein results have been adopted by the anti-helmet community to justify resistance to compulsory motorcycle helmet use on the grounds that helmets may cause neck injuries due to their mass. In the current study, we replicated Goldstein's models to understand how he obtained his unexpected results, and we then applied modern statistical methods to estimate the association of motorcycle helmet use with head injury, fatal injury, and neck injury among collision-involved motorcyclists. We found Goldstein's analysis to be critically flawed due to improper data imputation, modeling of extremely sparse data, and misinterpretation of model coefficients. Our new analysis showed that motorcycle helmets were associated with markedly lower risk of head injury (RR 0.40, 95% CI 0.31-0.52) and fatal injury (RR 0.44, 95% CI 0.26-0.74) and with moderately lower but statistically significant risk of neck injury (RR 0.63, 95% CI 0.40-0.99), after controlling for multiple potential confounders.

Hepatitis C Virus Reinfection and Spontaneous Clearance of Reinfection--the InC3 Study.

BACKGROUND: We aimed to characterize the natural history of hepatitis C virus (HCV) reinfection and spontaneous clearance following reinfection (reclearance), including predictors of HCV reclearance. METHODS: Data were synthesized from the 9 prospective cohorts of the International Collaboration of Incident Human Immunodeficiency Virus and HCV in Injecting Cohorts study, which evaluated HCV infection outcomes among people who inject drugs. Participants with primary HCV infection were classified as having achieved viral suppression if they had negative results of at least 1 subsequent HCV RNA test. Those with positive results of an HCV RNA test following viral suppression were investigated for reinfection. Viral sequence analysis was used to identify reinfection (defined as detection of heterologous virus with no subsequent detection of the original viral strain). RESULTS: Among 591 participants with acute primary HCV infection, 118 were investigated for reinfection. Twenty-eight participants were reinfected (12.3 cases/100 person-years; 95% confidence interval [CI], 8.5-17.8). Peak HCV RNA level was lower during reinfection than primary infection (P = .011). The proportion of individuals with reclearance 6 months after reinfection was 52% (95% CI, 33%-73%). After adjustment for study site, females with the IFNL4 (formerly IFNL3 and IL28B) rs12979860 CC genotype detected were more likely to have reclearance (hazard ratio, 4.16; 95% CI, 1.24-13.94; P = .021). CONCLUSIONS: Sex and IFNL4 genotype are associated with spontaneous clearance after reinfection.

Patterns of hepatitis C virus RNA levels during acute infection: the InC3 study.

BACKGROUND: Understanding the patterns of HCV RNA levels during acute hepatitis C virus (HCV) infection provides insights into immunopathogenesis and is important for vaccine design. This study evaluated patterns of HCV RNA levels and associated factors among individuals with acute infection. METHODS: Data were from an international collaboration of nine prospective cohorts of acute HCV (InC3 Study). Participants with well-characterized acute HCV infection (detected within three months post-infection and interval between the peak and subsequent HCV RNA levels ≤ 120 days) were categorised by a priori-defined patterns of HCV RNA levels: i) spontaneous clearance, ii) partial viral control with persistence (≥ 1 log IU/mL decline in HCV RNA levels following peak) and iii) viral plateau with persistence (increase or <1 log IU/mL decline in HCV RNA levels following peak). Factors associated with HCV RNA patterns were assessed using multinomial logistic regression. RESULTS: Among 643 individuals with acute HCV, 162 with well-characterized acute HCV were identified: spontaneous clearance (32%), partial viral control with persistence (27%), and viral plateau with persistence (41%). HCV RNA levels reached a high viraemic phase within two months following infection, with higher levels in the spontaneous clearance and partial viral control groups, compared to the viral plateau group (median: 6.0, 6.2, 5.3 log IU/mL, respectively; P = 0.018). In the two groups with persistence, Interferon lambda 3 (IFNL3) CC genotype was independently associated with partial viral control compared to viral plateau (adjusted odds ratio [AOR]: 2.75; 95%CI: 1.08, 7.02). In the two groups with viral control, female sex was independently associated with spontaneous clearance compared to partial viral control (AOR: 2.86; 95%CI: 1.04, 7.83). CONCLUSIONS: Among individuals with acute HCV, a spectrum of HCV RNA patterns is evident. IFNL3 CC genotype is associated with initial viral control, while female sex is associated with ultimate spontaneous clearance.

Interferon lambda 3 genotype predicts hepatitis C virus RNA levels in early acute infection among people who inject drugs: the InC(3) study.

BACKGROUND AND OBJECTIVES: Hepatitis C virus (HCV) RNA level in acute HCV infection is predictive of spontaneous clearance. This study assessed factors associated with HCV RNA levels during early acute infection among people who inject drugs with well-defined acute HCV infection. STUDY DESIGN: Data were from International Collaboration of Incident HIV and Hepatitis C in Injecting Cohorts (InC(3)) Study, an international collaboration of nine prospective cohorts studying acute HCV infection. Individuals with available HCV RNA levels during early acute infection (first two months following infection) were included. The distribution of HCV RNA levels during early acute infection were compared by selected host and virological factors. RESULTS: A total of 195 individuals were included. Median HCV RNA levels were significantly higher among individuals with interferon lambda 3 (IFNL3, formerly called IL28B) CC genotype compared to those with TT/CT genotype (6.28 vs. 5.39logIU/mL, respectively; P=0.01). IFNL3 CC genotype was also associated with top tertile HCV RNA levels (≥6.3log IU/mL; vs. TT/CT genotype; adjusted Odds Ratio: 4.28; 95%CI: 2.01, 9.10; P<0.01). CONCLUSIONS: This study indicates that IFNL3 CC genotype predicts higher HCV RNA levels in early acute HCV infection.

Driver obesity and the risk of fatal injury during traffic collisions.

BACKGROUND: Few studies have looked at how obesity affects injury outcomes among vehicle occupants involved in traffic collisions. OBJECTIVE: To estimate the association of obesity with death risk among drivers of passenger vehicles aged ≥16 and to examine effect modification by driver sex, driver seat belt use, vehicle type and collision type. METHODS: We conducted a matched-pair cohort study using data from the Fatality Analysis Reporting System. WHO body mass index (BMI) categories were calculated. Data were analysed using conditional Poisson regression. RESULTS: Estimated risk ratios (RRs) were slightly raised for underweight drivers (RR=1.19, 95% CI 0.86 to 1.63). RR increased with higher BMI categories and were 1.21 (0.98 to 1.49) for BMI 30-34.9, 1.51 (1.10 to 2.08) for BMI 35-39.9 and 1.80 (1.15 to 2.84) for BMI ≥40. Estimated BMI effects varied by gender. We found no meaningful variation across levels of vehicle type, collision type or seat belt use. CONCLUSIONS: Findings from this study suggest that obese vehicle drivers are more likely to die from traffic collision-related injuries than non-obese occupants involved in the same collision. Education is needed to improve seat belt use among obese people, as is research to understand the potential role of comorbidities in injury outcomes.

The effects of female sex, viral genotype, and IL28B genotype on spontaneous clearance of acute hepatitis C virus infection.

UNLABELLED: Although 20%-40% of persons with acute hepatitis C virus (HCV) infection demonstrate spontaneous clearance, the time course and factors associated with clearance remain poorly understood. We investigated the time to spontaneous clearance and predictors among participants with acute HCV using Cox proportional hazards analyses. Data for this analysis were drawn from an international collaboration of nine prospective cohorts evaluating outcomes after acute HCV infection. Among 632 participants with acute HCV, 35% were female, 82% were Caucasian, 49% had interleukin-28 (IL28)B CC genotype (rs12979860), 96% had injected drugs ever, 47% were infected with HCV genotype 1, and 7% had human immunodeficiency virus (HIV) coinfection. Twenty-eight percent were HCV antibody negative/RNA positive at the time of acute HCV detection (early acute HCV). During follow-up, spontaneous clearance occurred in 173 of 632, and at 1 year after infection, 25% (95% confidence interval [CI]: 21, 29) had cleared virus. Among those with clearance, the median time to clearance was 16.5 weeks (IQR: 10.5, 33.4), with 34%, 67%, and 83% demonstrating clearance at 3, 6, and 12 months. Adjusting for age, factors independently associated with time to spontaneous clearance included female sex (adjusted hazards ratio [AHR]: 2.16; 95% CI: 1.48, 3.18), IL28B CC genotype (versus CT/TT; AHR, 2.26; 95% CI: 1.52, 3.34), and HCV genotype 1 (versus non-genotype 1; AHR: 1.56; 95% CI: 1.06, 2.30). The effect of IL28B genotype and HCV genotype on spontaneous clearance was greater among females, compared to males. CONCLUSIONS: Female sex, favorable IL28B genotype, and HCV genotype 1 are independent predictors of spontaneous clearance. Further research is required to elucidate the observed sex-based differences in HCV control.

Predictors of nonstandard helmet use among San Francisco Bay-area motorcyclists.

OBJECTIVE: The use of helmets that do not comply with safety standards is common in California. The objective of this study was to describe the use of these nonstandard helmets among San Francisco Bay-area (SFBA) motorcyclists and to identify personal and motorcycle characteristics that are associated with the use of nonstandard helmets. METHODS: A survey of 860 SFBA motorcyclists was conducted. Log-binomial regression was used to estimate risk ratios to compare probabilities of nonstandard helmet use. RESULTS: Fifteen percent of motorcyclists reported wearing a nonstandard helmet sometimes or often. BMW riders had the lowest use of nonstandard helmet (5%) and Harley-Davidson riders had the highest use (51%). Among non-Harley-Davidsons, riders of cruiser-style motorcycles were 3.1 times as likely to wear a nonstandard helmet as riders of motorcycles of other styles. African American riders were more than twice as likely to use nonstandard helmets compared to riders with other self-reported race. DISCUSSION: Behavioral countermeasures are needed to improve motorcycle helmet choice in California. This study identified riders of Harley-Davidsons and riders of cruiser-style motorcycles of other brands as potential targets of interventions.

Substance use and HIV risk behavior among men who have sex with men: the role of sexual compulsivity.

The relationship between substance use, sexual compulsivity and sexual risk behavior was assessed with a probability-based sample of men who have sex with men (MSM). Stimulant, poppers, erectile dysfunction medication (EDM), alcohol use, and sexual compulsivity were independently associated with higher odds of engaging in any serodiscordant unprotected anal intercourse (SDUAI). The association of sexual compulsivity with SDUAI was moderated by poppers and EDM use. Behavioral interventions are needed to optimize biomedical prevention of HIV among substance using MSM.

Cohort profile: the international collaboration of incident HIV and hepatitis C in injecting cohorts (InC3) study.

The International Collaboration of Incident HIV and Hepatitis C in Injecting Cohorts (InC(3)) Study is an international multi-cohort project of pooled biological and behavioural data from nine prospective cohorts of people who inject drugs (PWID). InC(3) brings together researchers from Australia, Canada, USA and the Netherlands with expertise in epidemiology, biostatistics, clinical and behavioural sciences, virology and immunology to investigate research questions relevant to hepatitis C virus (HCV) and HIV outcomes. InC(3) was established to: (i) create a merged multi-cohort study of pooled data from well-characterized cohorts of PWID with prospective data on HIV and HCV infections, with a particular focus on HCV; (ii) facilitate new studies not possible within individual cohorts; and (iii) bring together researchers across disciplines to answer a broad range of research questions. Study cohorts identify acute HCV cases through follow-up of high-risk HCV antibody-negative PWID or through clinical referral networks. To date, data from 1986 to 2010 have been received from all contributing cohorts, with 821 HCV-infected and 1216 HCV-uninfected participants (overall, n = 2037). Data collected include demographics, host genetics, HCV ribonucleic acid testing, alanine aminotransferase testing, HIV/hepatitis B virus testing, HCV therapy, loss to follow-up and mortality. Potential collaborators should contact the InC(3) PI Dr Kimberley Page (kPage@psg.ucsf.edu) for further information.

Trauma Center-Based Surveillance of Nontraffic Pedestrian Injury among California Children.

INTRODUCTION: Every year in the United States, thousands of young children are injured by passenger vehicles in driveways or parking areas. Little is known about risk factors, and incidence rates are difficult to estimate because ascertainment using police collision reports or media sources is incomplete. This study used surveillance at trauma centers to identify incidents and parent interviews to obtain detailed information on incidents, vehicles, and children. METHODS: Eight California trauma centers conducted surveillance of nontraffic pedestrian collision injury to children aged 14 years or younger from January 2005 to July 2007. Three of these centers conducted follow-up interviews with family members. RESULTS: Ninety-four injured children were identified. Nine children (10%) suffered fatal injury. Seventy children (74%) were 4 years old or younger. Family members of 21 victims from this study (23%) completed an interview. Of these 21 interviewed victims, 17 (81%) were male and 13 (62%) were 1 or 2 years old. In 13 cases (62%), the child was backed over, and the driver was the mother or father in 11 cases (52%). Fifteen cases (71%) involved a sport utility vehicle, pickup truck, or van. Most collisions occurred in a residential driveway. CONCLUSION: Trauma center surveillance can be used for case ascertainment and for collecting information on circumstances of nontraffic pedestrian injuries. Adoption of a specific external cause-of-injury code would allow passive surveillance of these injuries. Research is needed to understand the contributions of family, vehicular, and environmental characteristics and injury risk to inform prevention efforts.

Psychological processes and stimulant use among men who have sex with men.

BACKGROUND: Prior research established that psychological factors are associated with the frequency of stimulant (i.e., cocaine, crack, and methamphetamine) use among substance-using men who have sex with men (MSM). The present investigation examined whether and how psychological factors are associated with engagement in any stimulant use in the broader population of MSM. METHODS: A probability sample of 879 MSM residing in San Francisco was obtained using random digit dialing from May of 2002 through January of 2003. Of these, 711 participants (81%) completed a mail-in questionnaire that assessed psychological factors and substance use. After accounting for demographic factors, a multiple logistic regression analysis examined correlates of any self-reported stimulant use during the past 6 months. Path analyses examined if the use of alcohol or other substances to avoid negative mood states (i.e., substance use coping) mediated the associations of sexual compulsivity and depressed mood with stimulant use. RESULTS: Younger age (adjusted OR [AOR]=0.58; 95% CI=0.47-0.70), HIV-positive serostatus (AOR=2.55; 95% CI=1.61-4.04), greater depressed mood (AOR=1.26; 95% CI=1.05-1.52) and higher sexual compulsivity (AOR=1.46; 95% CI=1.18-1.80) were independently associated with increased odds of stimulant use. Substance use coping partially mediated the associations of sexual compulsivity (ß(indirect)=0.11, p<.001) and depressed mood (ß(indirect)=0.13, p<.001) with stimulant use. CONCLUSIONS: Clinical research is needed to examine if interventions targeting sexual compulsivity and emotion regulation reduce stimulant use among MSM.

Implications of conducting trend analyses of emergency department visits using publicly released masked design variables.

STUDY OBJECTIVE: We examine whether using public National Hospital Ambulatory Medical Care Survey (NHAMCS) data with masked design variables produces different estimates, standard errors, and confidence intervals (CIs) for the temporal trend of overall and injury-related emergency department (ED) visits compared with using unmasked data housed at the Centers for Disease Control and Prevention. METHODS: We obtained counts of ED visits with their standard errors for unmasked data from published summaries from 1999 through 2006. Public files with masked design variables were used to estimate visit counts and rates with standard errors for each year, using the Taylor series linearization method. Weighted least squares linear regressions were used for trend analysis to estimate the annual change in visits. RESULTS: Compared with using unmasked data, using masked data produced similar estimates of overall ED visit counts and rates for each year from 1999 through 2006 but overestimated standard errors by 27% on average (range 12% to 45%). According to unmasked data, overall ED visit counts increased by 1.973 million annually (standard error 0.747; 95% CI 0.505 to 3.440 million [corrected] ). With masked data, the estimated change was 1.977 million visits annually (standard error 0.894; 95% CI -0.221 to 3.733 million [corrected] ). As for injury-related ED visit counts, masked data overestimated the standard error by 16% for trend. Although neither unmasked nor masked data suggested a statistically significant annual increase of overall or injury-related ED visit rate, masked data overestimated the standard error by 16%. CONCLUSION: Using masked public data overestimated standard errors for trend of counts and rates for overall and injury-related ED visits and resulted in wider CIs.

The inclusion of adult vehicle occupants in matched cohort studies of child restraint effectiveness: a study of potential bias.

OBJECTIVE: To determine whether either the inclusion of adults in matched cohort studies of passenger vehicle occupants or modification of age effects by collision severity biases child restraint risk ratios biases estimate of child restraint effectiveness. METHODS: Monte Carlo data simulations were conducted to represent 10,000 collision-involved vehicles carrying a mix of children and adults. The effects of age category, adult seat belt use, child seat belt use, and child safety seat use were set to known values. Age was a modifier of the adult and child seat belt risk ratios and of the safety seat RR, and crash severity was a modifier of the age RRs. We also created an association between restraint use and collision severity to confound the restraint-death risk associations. RRs were estimated using conditional Poisson regression and compared with the true values. RESULTS: Estimated RRs for death were identical to the simulated values. The average child safety seat RR was 0.42 (true value 0.42), and the average seat belt RRs for children were 0.54 (true value 0.54) for those aged 0-3 years and 0.61 (true value 0.61) for those aged 4-17. Age effects were also correctly estimated, 1.69 (true value 1.69) for those aged 0-3 and 1.35 (true value 1.35) for those aged 4-17. CONCLUSIONS: Neither the use of matched sets of adults and children nor the modification of age effects by collision severity biases estimates of child restraint effectiveness in matched cohort studies.

Geocoding police collision report data from California: a comprehensive approach.

BACKGROUND: Collision geocoding is the process of assigning geographic descriptors, usually latitude and longitude coordinates, to a traffic collision record. On California police reports, relative collision location is recorded using a highway postmile marker or a street intersection. The objective of this study was to create a geocoded database of all police-reported, fatal and severe injury collisions in the California Statewide Integrated Traffic Records System (SWITRS) for years 1997-2006 for use by public agencies. RESULTS: Geocoding was completed with a multi-step process. First, pre-processing was performed using a scripting language to clean and standardize street name information. A state highway network with postmile values was then created using a custom tool written in Visual Basic for Applications (VBA) in ArcGIS software. Custom VBA functionality was also used to incorporate the offset direction and distance. Intersection and address geocoding was performed using ArcGIS, StreetMap Pro 2003 digital street network, and Google Earth Pro. A total of 142,007 fatal and severe injury collisions were identified in SWITRS. The geocoding match rate was 99.8% for postmile-coded collisions and 86% for intersection-coded collisions. The overall match rate was 91%. CONCLUSIONS: The availability of geocoded collision data will be beneficial to clinicians, researchers, policymakers, and practitioners in the fields of traffic safety and public health. Potential uses of the data include studies of collision clustering on the highway system, examinations of the associations between collision occurrence and a variety of variables on environmental and social characteristics, including housing and personal demographics, alcohol outlets, schools, and parks. The ability to build maps may be useful in research planning and conduct and in the delivery of information to both technical and non-technical audiences.

The effectiveness of child restraint systems for children aged 3 years or younger during motor vehicle collisions: 1996 to 2005.

OBJECTIVES: We estimated the effectiveness of child restraints in preventing death during motor vehicle collisions among children 3 years or younger. METHODS: We conducted a matched cohort study using Fatality Analysis Reporting System data from 1996 to 2005. We estimated death risk ratios using conditional Poisson regression, bootstrapping, multiple imputation, and a sensitivity analysis of misclassification bias. We examined possible effect modification by selected factors. RESULTS: The estimated death risk ratios comparing child safety seats with no restraint were 0.27 (95% confidence interval [CI] = 0.21, 0.34) for infants, 0.24 (95% CI = 0.19, 0.30) for children aged 1 year, 0.40 (95% CI = 0.32, 0.51) for those aged 2 years, and 0.41 (95% CI = 0.33, 0.52) for those aged 3 years. Estimated safety seat effectiveness was greater during rollover collisions, in rural environments, and in light trucks. We estimated seat belts to be as effective as safety seats in preventing death for children aged 2 and 3 years. CONCLUSIONS: Child safety seats are highly effective in reducing the risk of death during severe traffic collisions and generally outperform seat belts. Parents should be encouraged to use child safety seats in favor of seat belts.

Effects of the California graduated driver licensing program.

PROBLEM: On July 1, 1998, in an effort to ameliorate the problem of high teenage driver crash rates, California implemented a graduated driver licensing system (GDLS). METHOD: Data on injury crashes of 16- and 17-year-old drivers from a pre-GDLS year were compared with data from two post-GDLS years. Per-capita crash rate ratios were adjusted for changes in crash rates of 25- to 34-year-old drivers, who were unaffected by the GDLS. Prevented numbers and 95% confidence intervals were estimated. RESULTS: Fatal or severe injury crash rates were significantly lower during each of the two post-GDLS years (adjusted rate ratios (RR)=0.72 and 0.83, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Significant rate reductions were observed for all crash types, particularly for struck object (RR=0.71 and 0.80, for 2000 vs. 1997 and 2001 vs. 1997, respectively) and non-collision (RR=0.63 and 0.72, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Minor injury crash rates were also lower during post-GDLS years (RR=0.87 and 0.90, for 2000 vs. 1997 and 2001 vs. 1997, respectively). Percent reductions were notably larger during the hours of the late night driving restriction (midnight-5 a.m.) (RR=0.79 and 0.87, for 2000 vs. 1997 and 2001 vs. 1997, respectively). SUMMARY: The implementation of the California GDLS was followed by large reductions in the rate of injury-producing motor-vehicle crashes. IMPACT ON INDUSTRY: This evaluation supports previous evidence that GDLS is an effective countermeasure to adolescent motor-vehicle crashes and their associated injuries. States with a traditional licensing system may prevent adolescent driver crashes by adopting a GDLS. Future studies should examine factors that influence teenager compliance with GDLS provisions and identify approaches to improving compliance.