The Iowa Graduated Driver Licensing program: effectiveness in reducing crashes of teenage drivers. Evaluation of California's graduated driver licensing program. Graduated drivers license programs and rural teenage motor vehicle fatalities. Michigan's graduated driver licensing program: evaluation of the first four years. Graduated driver licensing and teen traffic fatalities. Effects of the California graduated driver licensing program. Graduated driver licensing in Michigan: early impact on motor vehicle crashes among 16-year-old drivers. Effect of a graduated licensing system on motor vehicle crashes and associated injuries involving drivers less than 18 years-of-age. Evaluation of Iowa's graduated driver's licensing program. The effects of graduated driver licensing on hospitalization rates and charges for 16-and 17-year-olds in North Carolina. An evaluation of the New Zealand graduated driver licensing system. Does the Maryland graduated driver licensing law affect both 16-year-old drivers and those who share the road with them? Initial effects of graduated driver licensing on 16-year-old driver crashes in North Carolina. The crash reduction effectiveness of a network-wide traffic police deployment system. Graduated driver licensing programs and fatal crashes of 16-year-old drivers: a national evaluation. Specific and long-term effects of Nova Scotia's graduated licensing program. Graduated driver licensing in Wisconsin: does it create safer drivers? Graduated driver licensing in Utah: is it effective? Reduction of young driver crashes in a controlled pilot study: two-year follow-up in one Michigan high school. California's graduated driver license law: Effect on teenage drivers' deaths through 2005.
Graduated Driver Licensing (GDL) programs vary in the United States in terms of implementation and restrictions. The State of Iowa's GDL program is assessed for its effectiveness in reducing crashes among teenage drivers.
                Time series analysis was used to evaluate police documented crashes involving 16-, 17-, and 18-year-old drivers over a 10 year period, with an intervention identified at the point of GDL implementation.
                After controlling for seasonal trends and auto-correlative effects, a significant reduction in the crash rate of and 16- and 17-year-old drivers was observed due to the GDL implementation. However, there were no significant reductions in crash rates for 18-year-old drivers.
                The analyses suggest that the Iowa GDL program is effective in reducing the crash rates of 16- and 17-year-old drivers but the effects do not sustain for 18-year-old drivers.
                The results suggest that the program appears to be working, however further analysis is needed to determine what factors are preventing lasting effects for these teenage drivers. California's graduated driver licensing (GDL) program was implemented to reduce the high crash risk of teenage drivers. The program enhancements made in 1998 were evaluated in this study using methods that rule out the noticeable downward trend in California teen's fatal/injury crash rates as a possible explanation for any observed crash reductions that could otherwise be mistaken for program effects.
                Monthly per capita fatal/injury crash rates for 15-to-17-year-olds and proportional representations of 16-17-year-olds' nighttime and passenger crashes were analyzed using intervention time series analysis.
                After removing trend, seasonality, and transition effects in the data, no overall reductions in fatal/injury crashes for 15-17-year-olds or 16-year-olds (separately) were found to be associated with the 1998 program enhancements, suggesting no overall exposure reduction effect of the longer instruction permit period nor increased competency associated with the higher number of required practice hours. However, the 12-month nighttime and 6-month passenger restrictions were found to be associated with annual savings of 55 and 816 fatal/injury crashes, respectively.
                Finding no overall impact of the 1998 GDL enhancements was not surprising given findings of an earlier survey suggesting that California teens and parents were largely already practicing program requirements prior to implementation and were not fully complying with the program requirements afterwards. Though the observed crash savings associated with the restrictions were of modest size, this is the first study to evidence a direct positive impact of the passenger restriction component of GDL programs. Larger reductions could be realized if the nighttime restriction started earlier and parents/law enforcement could be motivated to better enforce these restrictions.
                The findings provide support for passenger and nighttime restriction components of GDL programs. Graduated drivers license (GDL) programs have been shown to reduce motor vehicle fatalities among 15- to 17-year-olds. However, the 20 most rural states have been the least likely to enact more stringent GDL policies.
                Estimate the relationship of GDL programs and the number of traffic fatalities among 15- to 17-year-olds on rural interstate and noninterstate roadways.
                Analysis of 1992-2002 Fatality Analysis Reporting System data and a compendium of state laws using a conditional negative binominal regression model with full fixed effects to control for unobservable differences across states and years.
                Overall, GDL programs were associated with a 7.8% reduction in rural traffic fatalities among 15- to 17-year-olds. Virtually all of this reduction took place on noninterstate roadways. The most stringent GDL programs were associated with a nearly 22% reduction in this age group and were the only programs associated with reductions in fatalities among 15- to 17-year-old drivers.
                Rural states should consider enacting stringent GDL programs. Had the 19 of the 20 most rural states without such programs all adopted the most stringent GDL programs in 2002, the analysis suggests that 64 traffic deaths among 15- to 17-years-olds could have been prevented. To evaluate the four-year outcome of Michigan's graduated driver licensing (GDL) program, motor-vehicle crash data for 16-year-old drivers in 1996 (pre-GDL), and 1998-2001 (post-GDL) were analyzed.
                Relative risks and 95% confidence intervals for several crash types were computed, and pre-post-GDL population-based crash rates were compared. Reductions in crash risks among 16-year-olds previously found in 1998 and 1999 were generally maintained in 2000 and 2001.
                Reductions in crash risk among 16-year-olds from 1996 to 2001 were 29% for all, 44% for fatal, 38% each for nonfatal-injury and fatal-plus-nonfatal-injury, 32% for day, 31% for evening, 59% for night, 32% for single-vehicle, and 28% for multi-vehicle crashes. Even after adjusting for more general population-wide changes among drivers 25 years and older that might have contributed to changes in 16-year-old crash risk, reductions remained impressive (19% for all crashes in 2001).
                As one approach to reducing teenage motor-vehicle morbidity and mortality, GDL remains promising. Over the last 8 years, nearly every state has introduced graduated driver licensing (GDL) for teens. These new licensing procedures require teen drivers to advance through distinct stages where they are subject to a variety of restrictions (e.g., adult supervision, daytime driving, passenger limits). In this study, we present evidence on whether these restrictions have been effective in reducing traffic fatalities among teens. These evaluations are based on state-by-year panel data from 1992 to 2002. We assess the reliability of our basic inferences in several ways including an examination of contemporaneous data for older cohorts who were not directly affected by these policies. Our results indicate that GDL regulations reduced traffic fatalities among 15-17-year-olds by at least 5.6%. We also find that the life-saving benefits of these regulations were plausibly related to their restrictiveness. And we find no evidence that these benefits were attenuated by an increase in fatality risks during the full-licensure period available to older teens. 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).
                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.
                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).
                The implementation of the California GDLS was followed by large reductions in the rate of injury-producing motor-vehicle crashes.
                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. Graduated driver licensing (GDL) programs are being adopted in many states to address the high rate of motor vehicle fatalities among teens by requiring teenaged drivers to gain experience and maturity under conditions of relatively low crash risk before gaining full driving privileges.
                To evaluate the early impact of Michigan's GDL program on traffic crashes among 16-year-old drivers.
                Analysis of Michigan motor vehicle crash data from 1996 (before GDL program implementation) vs 1998 and 1999 (after GDL program implementation) for 16-year-olds, adjusting for trends among persons 25 years or older.
                Michigan's GDL program, instituted April 1, 1997, for teens younger than 18 years entering the driver license system, includes 3 licensure levels, each with driving restrictions and requirements to progress to the next level. Requirements include extended, supervised practice in the learning level, 2-phase driver education, and night driving restrictions in the intermediate level.
                Rates in 1996 vs 1998 and 1999 for all police-reported crashes; for fatal injury, nonfatal injury, and fatal/nonfatal injury combined crashes; for day, evening, and night crashes; for single-vehicle and multivehicle crashes; and for alcohol-related crashes.
                Overall, the rate of 16-year-old drivers (per 1000 population) involved in crashes declined from 154 in 1996 to 111 in 1999 (relative risk [RR], 0.72; 95% confidence interval [CI], 0.71-0.73). After adjusting for populationwide trends, the overall crash risk for 16-year-olds was significantly reduced in 1999 from 1996 by 25% (adjusted RR, 0.75; 95% CI, 0.74-0.77). There were also significant reductions for nonfatal injury and combined fatal and nonfatal crashes; for day, evening, and night crashes; and for single-vehicle and multivehicle crashes. Fatal crashes declined from 1996 to 1999, but not significantly (RR, 0.74; 95% CI, 0.49-1.14), and alcohol-related crashes continued at a low rate (RR, 1.01; 95% CI, 0.80-1.29).
                Analysis of the first 2 full calendar years following Michigan's GDL program implementation indicates substantial crash reductions among 16-year-olds. Future research is necessary to determine if these reductions are maintained and if other jurisdictions achieve similar results. The rate of motor vehicle crashes in the United States is higher among adolescent drivers than among any other age group. This study was conducted to determine whether implementation of a graduated driver's licensing program is associated with a reduced the rate of motor vehicle crashes and injuries involving adolescent driver.
                Time periods before and after establishment of Delaware's GDL program were compared. The one year "before" period spanned January 1, 1998, through December 31, 1998, and the 3-year "after" period spanned January 1, 2000, to December 31, 2002. Following enactment of the GDL program on July 1, 1999, we delayed data collection during the "after" period for 6 months to allow for full implementation of the program. Information was obtained for all Delaware registered drivers between ages 16 and 17 years were involved in motor vehicle crashes involving property damage or injury from 1998 to 2002. The rate of crashes involving property damage, EMS transport, injury, hospitalization, and death were determined pre- and post-GDL,. Length of hospitalization and hospital charges were compared, and the presence and age of passengers, along with time of day were determined.
                The total number of licensed 16- and 17-year-old drivers in Delaware was 14,320 during 1998 (the before period), 16,849 for 2000, 14,098 for 2001, and 14,276 for 2002, for a total of 45,223 licensed drivers studied during the after period. The proportion of hospitalizations, injuries, crashes involving property damage and total number of crashes involving registered 16- and 17-year-old drivers after GDL each decreased by at least 30%. In addition, this GDL program was associated with a reduction in nighttime crashes and in crashes involving cars with multiple passengers in comparison with the time period before GDL.
                Two years after implementation, the hospitalization rate, injury rate, and crash rate decreased significantly with enactment of the GDL program in the State of Delaware. The Delaware's GDL program appears successful in decreasing motor vehicle crashes and resultant injuries in adolescent drivers. The effectiveness of Iowa's graduated driver's licensing (GDL) program was evaluated for a 4-year period before and after implementation in 1999. Since some changes had occurred in the crash reporting format, changes in crash rates for younger drivers were compared to those for 35-44-year-old drivers (middle-age group of drivers) who were used as a control group. After implementation of GDL, the 14-, 16- and 17-year-old age groups experienced a greater decrease in crash rate than the middle-age control group while 15-year-old experienced a smaller decrease. This suggests that the crash rate for 15-year-old drivers may actually have increased when downward trends were adjusted for. Iowa's GDL program allows holders of the instruction permit to travel unaccompanied to and from school and school-endorsed activities after obtaining a minor school license. Fifteen-year-old with minor school licenses account for up to 26.7% of 15-year-old license holders yet represent up to 74.8% of 15-year-old drivers involved in crashes (depending on the year) from 1998 to 2004. As a result, 15-year-old drivers with minor school licenses are involved in 7.2-8.9 times more crashes, are 7.7 times more likely to have one or more sanctions, and are 4.8 times more likely to receive one or more moving convictions than their peers with a regular instruction permit. This help may explain why 15-year-old drivers did not seem to benefit from implementation of the GDL program in Iowa. To mitigate the high risk of motor vehicle crashes for young beginning drivers, over 40 states and the District of Columbia have implemented graduated driver licensing (GDL) systems that gradually and systematically ease teen drivers into higher risk driving conditions. Evaluations of GDL programs using motor vehicle crash data have demonstrated marked declines in crashes. The objective of this study is to examine the association between the implementation of the North Carolina GDL program and the rate of hospitalization, as well as hospital charges, for 16-and 17-year-old drivers.
                Data were obtained from the North Carolina Hospital Discharge Database for the 26 months before and 46 months after the December 1, 1997, implementation of the GDL program. ARIMA interrupted time series analyses were used to model monthly hospitalization rates, controlling for the hospitalization rates of 25-to 54-year-old drivers. ARIMA analyses were also used to determine whether changes occurred in monthly total hospital charges.
                Among the 568 16-year-old hospitalized drivers, GDL was associated with a 36.5% decline in the hospitalization rate per population and a 31.2% decline in the total monthly driver hospitalization charges. Although a 12% reduction in the rate of hospitalizations was observed among the 615 17-year-old drivers, the analysis lacked sufficient power to be statistically reliable. No consistent change was observed in the 16-year-old driver total monthly hospital charges.
                The North Carolina GDL program was associated with a marked decline in the rate of hospitalizations and hospital charges for 16-year-old drivers. Following the implementation of GDL, over $650,000 in hospital charges have been averted each year for 16-year-old drivers. Analyses suggest these reductions were primarily the result of reduced exposure rather than an improvement in teen driving. Young drivers have a disproportionately high risk of experiencing a road traffic crash. On 1 August 1987 a Graduated Driver's Licensing System (GDLS) was introduced in New Zealand. This system was designed to give young drivers (i.e. 15-24 years inclusive) experience in driving while being excluded from high risk driving situations. We sought to determine the impact of the GDLS on serious injury crashes. The source of the injury crash data was New Zealand's Health Information Services' national public hospital inpatient morbidity data files for the years 1979-1992 inclusive. We disaggregated the occupant data into three age groups 15-19 years, 20-24 years, and persons 25 years of age or older and compared their trends in injury. In order to determine whether the incidence of motor vehicle crashes was simply following trends in other injury events we also included two 15-19 year old non-traffic injury comparison groups. Using time series analyses we showed that the introduction of the GDLS was closely followed by substantial reductions in car crash injuries for all age groups, especially 15-19 year olds (23% reduction). After considering effects for older occupants we speculate that the effect is likely to be substantially less than 23%. An analysis of licensure data suggests that the reduction in crashes may, in large part, be attributable to an overall reduction in exposure. To assess effects of the 1999 Maryland graduated driver licensing (GDL) law on both 16-year-old drivers and other road users.
                Calculation and comparison of crash involvement rates and non-fatal injury rates pre-GDL (1996-1998) and post-GDL (2001-2003) by type of road user, per population, and per licensed driver, with adjustment for trends among 30-59-year-old drivers.
                Post-GDL, prevalence of licensure decreased 24% among 16-year-olds, and rates of 16-year-old drivers involved in crashes significantly decreased per 16-year-old population (corrected rate ratio (RRc) 0.82; 95% CI (0.71, 0.96)). A significant decrease also was observed for non-fatal injuries per 16-year-old population among 16-year-old drivers involved in crashes (RRc 0.63; 95% CI (0.41, 0.98)). Similarly, decreases, albeit not statistically significant, were observed among their passengers and other vehicle occupants. Per 16-year-old licensed driver, a slight non-significant increase was observed in crash involvement rates; non-fatal injury rates per 16-year-old licensed driver suggest decreased risk (non-significant) among 16-year-old drivers, their passengers, and other vehicle occupants.
                Maryland's GDL delayed licensure and reduced crashes and non-fatal injuries among 16-year-old drivers per population. Trends in injuries among other road users involved in crashes with 16-year-old drivers were suggestive of a benefit from GDL, although observed decreases were not significant. Per licensed driver, findings were not significant, but suggested little change in crash involvement and decreased non-fatal injuries. Because one-third fewer 16-year-olds were licensed post-GDL, these results may suggest a selection effect in licensure.
                Because Maryland had nighttime restrictions for new drivers before 1999, this study suggests other components of GDL are beneficial for drivers and possibly for other road users. States with weak GDL laws should strongly consider revising them. Since 1997, 32 states have enacted graduated driver licensing (GDL) systems to reduce crash rates among young novice drivers.
                To determine the initial effect of the North Carolina GDL system on crashes among 16-year-old drivers.
                Comparison of population-based North Carolina motor vehicle crash rates before (1996-1997) and after (1999) 16-year-old drivers were licensed under the GDL system. To control for other factors that might have influenced crashes, changes for 16-year-old drivers were compared with those of drivers 25 to 54 years of age. Crashes per licensed driver were also examined.
                The North Carolina GDL system, enacted December 1, 1997, requires beginning drivers 15 to 17 years of age to hold level 1 licenses, allowing driving only while supervised by a designated adult for a full year; followed by level 2 licensure, allowing unsupervised driving from 5 AM to 9 PM and supervised driving at any time for at least 6 months; and, finally, level 3-a full, unrestricted license.
                Rates of motor vehicle crashes among 16-year-old drivers in 1996-1997 vs 1999, overall and by crash severity (fatal, injury, and noninjury), time (night vs day), type (single vs multiple vehicle), driver alcohol use, and driving environment (more vs less rural counties).
                Crash rates declined sharply for all levels of severity among 16-year-old drivers after the GDL program was implemented. Following GDL, 16-year-old driver crashes were substantially less likely. Comparing 1996 with 1999, fatal crashes declined 57%, from 5 to 2 per 10 000 population (rate ratio [RR], 0.43; 95% confidence interval [CI], 0.27-0.70); crashes with no or minor injuries decreased 23%, from 1068 to 826 per 10 000 (RR, 0.77; 95% CI, 0.75-0.80). Nighttime crashes were 43% less likely (156 vs 88 per 10 000; RR, 0.57; 95% CI, 0.52-0.61) and daytime crashes decreased by 20% (951 vs 764 per 10 000; RR, 0.80; 95% CI, 0.78-0.83). Single-vehicle crashes (245 vs 175; RR, 0.71; 95% CI, 0.67-0.76) declined somewhat more than multiple-vehicle crashes (866 vs 681; RR, 0.79; 95% CI, 0.76-0.81).
                In its initial years, the North Carolina GDL system produced substantial declines in 16-year-old driver crashes. Random Road Watch (RRW) is a traffic policing program in operation in Queensland, Australia. It differs from conventional traffic policing in that an explicit resource management technique is used which randomly schedules low levels of police enforcement in a manner intended to provide long-term, widespread coverage of a road network and hence maximise road safety benefits. Implementation of the program studied in Queensland covered 55% of total crashes within the state. This study aimed to measure the crash effects of the RRW program in Queensland. A quasi-experimental study design was used for the evaluation incorporating Poisson regression statistical analysis techniques. Analysis of the effects of the Queensland RRW program on crash frequency has shown the program to be effective overall. Estimated program effects were largest on fatal crashes, with an estimated reduction of 31%. Estimated aggregate program crash effects reduced with crash severity and increased with time after program introduction. Crash reductions in the third year after program introduction translated into savings, at state level, of some 12% of the state's crashes of all severities and some 15% of the state's fatal road crashes. Overall, the program produced a significant 11% reduction in total crashes in areas outside of metropolitan Brisbane. The opportunity-cost benefit/cost ratio for the program was estimated to be 55:1. Implementation of graduated driver licensing programs is associated with reductions in crash rates of young drivers, but graduated driver licensing programs vary in their components. The impact of programs with different components is unknown.
                The purpose of this work was to determine which graduated driver licensing programs are associated with the greatest reductions in fatal motor vehicle crashes involving 16-year-old drivers.
                We conducted a retrospective study of all 16-year-old drivers involved in fatal crashes in the United States from 1994 through 2004 using data from the Fatality Analysis Reporting System and the US Census Bureau. We measured incidence rate ratios of fatal motor vehicle crashes involving 16-year-old drivers according to graduated driver licensing programs, adjusted for state and year.
                Compared with state quarters with no graduated driver licensing program components, reductions of 16% to 21% in fatal crash involvement rates of 16-year-old drivers occurred with programs that included > or = 3-month mandatory waiting period, nighttime driving restriction, and either > or = 30 hours of supervised driving or passenger restriction. Reductions of 18% to 21% occurred in state quarters with programs that included > or = 5 of the 7 components examined. Drivers aged 20 to 24 or 25 to 29 years did not experience significant reductions.
                Comprehensive graduated driver licensing programs are associated with reductions of approximately 20% in 16-year-old drivers' fatal crash involvement rates. The greatest benefit seems to be associated with programs that include age requirements and > or = 3 months of waiting before the intermediate stage, nighttime driving restriction, and either > or = 30 hours of supervised driving or passenger restriction. A graduated licensing (GL) program was introduced in Nova Scotia, Canada, in October 1994. Previous research has shown that it reduced collisions in the short term. The present study examined the relative contribution of each stage of the program (i.e., learner and intermediate levels) and the program's impact after beginning drivers graduated to full licensure. The research focused on teenage beginning drivers (age 16-17), but the effects on older beginners also was examined. Per-driver crash rates of two groups of novices selected from driver records in Nova Scotia were compared. One group (pre-GL) received their learner's permits during the 2 years before the program was implemented, and the second group (GL) received their learner's permits during the 2 years after implementation. The findings clearly establish that most of the collision reduction in Nova Scotia's program occurred during the first year of the program, particularly during the first 6 months when the majority of novices were driving under supervision. The collision rate for 16 to 17-year-old GL novices was 50% lower than the rate for pre-GL novices during the 6 months after they received their learner's permits, and about 10% lower during their first 2 years of licensure when unsupervised driving from midnight to 5 A.M. was prohibited. Much of this improvement for 16 to 17-year-olds occurred during restricted night hours. Collision rates also were lower during nonrestricted hours in the initial 6 months of licensure. The 3-month "time discount" for driver education provided no safety benefit, and GL novices with driver education had collision rates that were not lower than pre-GL novices. There was no long-term effect found for the program after 16 to 17-year-olds graduated to full licensure. For older beginning drivers, crash rates during the first year after obtaining a learner's permit showed a 31% reduction. This effect diminished rapidly. There was only a 2% reduction during the first year of licensure, and crash rates increased during the following 2 years. Overall the data indicate substantial benefits of graduated licensing for 16 to 17-year-old beginners, but no benefits beyond the learner stage for older beginners. The purpose of this study was to measure the effectiveness of Wisconsin's graduated driver licensing law and determine whether a reduction in crash rates was due to reduced exposure, safer driving, or both.
                General population crash rates for 16 and 17 year olds were computed for years before and after graduated drivers licensing. The induced exposure method was used to measure exposure and compute the odds ratio of at-fault crash involvement.
                For 16 year olds, general crash rates declined 13.8% while injury crash rates declined 15.6%. For 17 year olds, crash rates declined 6.2% for all crashes and 5.8% for injury crashes. There was no statistically significant change in the odds ratio of at-fault crash involvement for 16- or 17-year-old drivers, relative to the reference group. After graduated drivers licensing, 16-year-old drivers were more likely to have at least 1 adult present and less likely to carry 2 or more teen passengers. There was no statistically significant effect on driving habits by time for 16 year olds.
                Graduated driver licensing in Wisconsin has resulted in a drop in the general population crash rates for 16 and 17 year olds. This decrease is the result of reduced exposure to the risk of collision rather than safer driving by teens. We seek to examine the effectiveness of the graduated driver licensing system in Utah by determining whether crash rates of 16-year-old drivers decreased after graduated driver licensing implementation.
                We studied 16-year-old-driver crashes using statewide motor vehicle crash data probabilistically linked to emergency department (ED), hospital inpatient, and driver licensure data for 1996 to 2001. Outcomes examined included overall crash rates, nighttime crashes, crash severity indicators (eg, noninjury crash, injury crash, ED crash, inpatient crash, fatal crash), seat belt usage, licensure status, and citations. Rate ratios (RR), chi 2 tests, and interventional time series analyses were used to assess changes before and after graduated driver licensing implementation.
                There were 27,304 16-year-old-driver crashes during the study period. The overall crash rate per 1,000 licensed 16-year-old drivers decreased by 5% (RR 0.95; 95% confidence interval [CI] 0.92 to 0.97), and a time-series analysis showed a reduction of 0.8 (SD 0.39) crashes per month per 1,000 licensed drivers after graduated driver licensing implementation (1996 to 1999 versus 1999 to 2001). The nighttime crash rate did not change (RR 0.91; 95% CI 0.78 to 1.04), and there was no association between crash severity and graduated driver licensing implementation ( P =.096). Reported seat belt usage increased by 6.3%, and few graduated driver licensing citations were issued by law enforcement.
                The results suggest that graduated driver licensing may have contributed to a reduction in young driver crashes, but the effects were minimal compared with those shown in many other graduated driver licensing evaluations. nan While many researchers believe Graduated Driver Licensing (GDL) laws save lives by imposing restrictions and delayed licensure on drivers under age 18, longer term effects on older teenagers have not been studied.
                The effects of California's strict GDL law on deaths of drivers ages 16-19 were analyzed for 1995-2005 using Incidence Rate Ratios (IRR) and Auto-Regressive Integrated Moving Average (ARIMA) time series analysis of Fatality Analysis Reporting System mortality data.
                The two methods yielded similar results. IRR analysis found California 16-year-old drivers subject to the GDL experienced a 15% fatality decline (95% CI, 0.70-0.99), while 18 year-old drivers experienced a 15% increase (95% CI, 1.02-1.27). ARIMA analysis found 16 year-old drivers experienced a near-significant 20% fatality decline (p=0.07), while 18 year-olds experienced a 24% increase (p=0.01). Unlicensed teenage drivers and older teen drivers driving alone and transporting teenage passengers suffered significant fatality increases.
                California's GDL may negatively affect older teenagers and other driver subpopulations and merits reevaluation.
GDL is effective in reducing crash rates among young drivers, although the magnitude of the effect varies. The conclusions are supported by consistent findings, temporal relationship, and plausibility of the association. Stronger GDL programs (i.e. more restrictions or higher quality based on IIHS classification) appear to result in greater fatality reduction. Future studies should focus on which components and combination of components yield the greatest reductions.