Effectiveness of graduated driver licensing in reducing motor vehicle crashes

Abstract

Objective: To determine whether graduated driver licensing (GDL) systems and nighttime curfews reduce motor vehicle crashes, fatalities, or injuries among young drivers.

Methods: We used Cochrane Collaboration search strategies to locate studies of graduated licensing or night driving restrictions. Studies were selected if they examined the effects of either (1) a comprehensive graduated driver licensing system including well-integrated components, or (2) nighttime driving restrictions/curfews that could affect young persons’ nighttime driving, on a clearly defined crash or injury outcome. Seven studies met inclusion criteria.

Results: Two independent studies of the New Zealand graduated licensing program found a sustained 7%–8% reduction in teen driver crash injuries attributable to the program. No other full graduated licensing system has been evaluated to date. Four studies of either a general curfew or a nighttime driving restriction for teens, a key element of graduated licensing, found substantial crash reductions during restricted hours, with 23%–25% lower crash injury and fatality rates for curfews beginning prior to midnight. One study found no change in late night crashes before and after a 1 a.m.–6 a.m. night driving restriction took effect.

Conclusions: The logic and empirical bases for graduated licensing are sound. Moreover, there is evidence that one central element, a restriction on nighttime driving by novices, reduces young driver crashes. However, a definitive conclusion about the effectiveness of GDL systems for reducing motor vehicle crashes or crash-related injuries must await examination of other GDL systems. This should be possible within the next few years, as several states and Canadian provinces have recently enacted GDL programs.

Introduction

Teen drivers in the United States have a high motor vehicle crash rate. In 1996, young drivers (aged 15–20 years old) were involved in 14.4% of all fatal crashes, even though they comprised only 8.4% of the U.S. population and about 6.7% of licensed drivers.1 Teen drivers (aged 16–19) have the highest crash rates of all drivers in the United States on both a per capita and per licensed driver basis.2 Partly because of these high crash rates, and partly because teens tend to ride mainly with other teens,3 motor vehicle crashes account for 40% of deaths among this age group.4 Approximately half of all teens who die in motor vehicle crashes are drivers. Nearly two thirds of teens who die as passengers are riding with a teenage driver. However, young drivers are also a threat to road users other than themselves and their passengers. Approximately 20% of all motor vehicle passenger fatalities, regardless of victim age, occur in crashes involving a teenage driver.5 In North Carolina, 41% of persons injured in crashes caused by 16-year-old drivers are occupants of other vehicles.6 Nighttime driving is more risky for all drivers, but this is particularly so for young drivers. In North Carolina, for example, between the hours of 10 p.m. and midnight, 16-year-old drivers are 3.2 times more likely than 21–59-year-old drivers to have a crash, after adjusting for the amount of driving during those hours.7

There has not been a great deal of research on young driver behavior that can inform efforts to reduce this substantial problem. For years far too much faith was placed in the value of formal driver education programs for ensuring that new drivers are safe. A careful, extensive evaluation of a driver education program conducted in Dekalb County, Georgia, found few if any safety benefits of this kind of education.8 This result is particularly noteworthy because the program evaluated was much more extensive that the standard driver education curriculum. A recent review of several studies of driver education also concludes that high school– aged drivers who take driver education courses have no fewer crashes or violations than those who do not complete such a course.9 Similarly, testing of driver skills and knowledge has proved to be inadequate for detecting and preventing unsafe drivers from obtaining a license.10

There has been dramatic progress in reducing a prime contributor to crashes among young drivers: alcohol use. The increase in the legal drinking age to 21 in all states in the mid-1980s was associated with a marked decline in alcohol-involved fatal crashes, especially among 16- and 17-year-old drivers.1, 11 However, this did not produce a corresponding decline in young driver fatal crashes, which remained relatively constant from 1982 to 1989, decreasing a mere 4% while alcohol involvement declined by more than 32%.11 Indeed, there has been an alarming increase in fatal crash rates among 16-year-old drivers (that is, among novices) in recent years, even as fatal crashes have declined among other age groups.12 In sum, young beginning drivers have inordinately high crash rates and to date we have been unable to alter this.

Although the research literature on young drivers is not extensive, there is general consensus that teens’ elevated crash rates are due to their lack of practical driving experience and to impulsiveness or poor judgment and decision-making.13, 14 Although not at all clearly understood, the latter appears to be a function both of inexperience and the limited psychological/emotional development that characterizes adolescents at the age when most currently begin driving legally in the United States.

Graduated driver licensing (GDL) is an approach to driver licensing first suggested a quarter century ago15 that has only recently been widely embraced as both desirable and feasible. GDL is designed to help novices learn a complex behavior, where mistakes can be life-threatening, by introducing them to driving in stages. GDL is a promising approach to reducing young driver crashes because it is designed to address both of the prime contributors to young driver crashes: inexperience and impulsiveness.16

Graduated licensing is a concept rather than a specific system. In principle, under a GDL system, beginning drivers progress through a series of levels wherein they obtain substantial driving experience under real world conditions, which is considered essential to becoming a good driver. The levels are characterized by the degree of risk involved. At the initial level, risks to beginning drivers (as well as to others in the vehicle and on the road) are substantially controlled. As drivers gain experience and demonstrate competence, they progress to levels with fewer restrictions, and, therefore, more of the typical risks attendant to driving. Risk is controlled at each level by limitations on when, where, and under what conditions novice drivers are permitted to drive. Ideally, progression from one level to the next is contingent on a demonstration of driving competence rather than being based on age or time spent at a level. Hence, GDL implements a degree of societal responsibility for young persons’ safety by ensuring that they begin driving in the safest possible situations. At the same time it requires responsibility from individuals, who must meet a series of minimum standards of success or competence before being awarded unlimited driving privileges.

Because it is a concept rather than a simple clearly defined system, there has been substantial confusion about what constitutes graduated licensing. In determining whether a licensing system is truly a GDL system, the critical issue is not how many stages exist, nor which limitations are in place. Rather, the question is whether a licensing system is designed in such a way that novice drivers progress from less to more risky driving conditions as they obtain required experience and that they are required to demonstrate appropriately safe driving behavior to progress (i.e., graduate) from one level to the next. Rudimentary versions of the GDL concept have been in effect for years in states that require (rather than merely allow or encourage) beginning drivers to spend some time under a Learner’s permit, which entails supervision of beginning drivers by another licensed driver in the vehicle.

A full GDL system can have any number of stages, but a minimum of three is generally considered necessary to adequately implement the concept. Essential stages include an initial period of several months of supervised driving, followed by a period of unsupervised driving that is still limited to less risky situations (e.g., during daytime hours, or with no teen passengers), leading finally to essentially unrestricted licensure. In principle, GDL can involve a variety of other elements that provide for a safer learning environment and encourage a greater motivation on the part of beginning drivers to drive safely.

In 1996, the National Committee on Uniform Traffic Laws and Ordinances (NCUTLO) convened a panel of experts on young drivers and driver licensing, including representatives of various government agencies and private organizations that endorse GDL, to develop a model Graduated Driver Licensing law. That model has become generally accepted as the standard definition of elements needed to qualify as a genuine graduated driver licensing system. In brief, the NCUTLO model involves the following:¹

• Three stages or levels: Learner, Intermediate, and Full

• Learner level constraints on drivers:

• Supervision when driving by a parent, guardian, or other licensed adult age 21 or older

  • Seat belt use by all vehicle occupants riding with the novice driver

  • Maintenance of a conviction-free driving record for at least 6 continuous months to graduate to the Intermediate level

• Intermediate level constraints on drivers:

• Supervision while driving between the hours of 10 p.m. and 5 a.m.

  • Seat belt use by all vehicle occupants

  • Maintenance of a conviction-free driving record for at least 6 continuous months to graduate to Full License level

• Full License level constraints on drivers:

• None other than adherence to all existing traffic laws (which applies at all levels)

The model law contains a variety of other details pertaining to testing requirements, provisions for penalties for various violations, and other elements that are typically elements of state driver licensing statutes. However, the above represent the principal elements designed to limit risk and promote safe driving practice during the early phases of licensed driving. Supervision by an adult ensures a safer driving environment by greatly controlling young driver impulsiveness; it also makes available the savvy of an experienced driver to the novice. The requirement of belt use ensures protection of all occupants in recognition of the fact that a beginning driver is more likely to crash. It also discourages “antics” within the vehicle that present a serious distraction, and increased crash risk, for inexperienced drivers.17 The prohibition of unsupervised nighttime driving during the intermediate level recognizes that this is a very high risk time for young drivers.² Since persons at the intermediate level are driving on their own for the first time (which increases both their freedom and their risk), risk is controlled by specifying that they may only drive during a lower risk time of day; if they are to drive at a high-risk time, the protective effect of a supervisor should be retained.

The dictate that conviction-free driving be achieved for a specified period of time requires novice drivers to demonstrate at least some evidence of safe driving behavior before protective restrictions of their license are removed. This recognizes that “driving attitude” is a central element in, and more predictive of, safe driving than are the kinds of knowledge assessed by standard testing. Thus, in addition to providing for a safer learning environment, a well-integrated GDL system emphasizes that driving is a privilege to be earned by demonstrating safe driving behaviors—typically over a period of time—rather than a right based merely on reaching a certain age and passing a minimal standard test. This is another way in which GDL addresses young driver impulsiveness. By mandating that a minimum of several months be spent at each level, the system encourages novice drivers to obtain ample practice, rather than merely spending a few hours acquiring rudimentary vehicle handling skills.

This review was undertaken to locate and summarize evaluations either of Graduated Driver Licensing systems or of programs that limit nighttime driving by young, inexperienced drivers, as the latter is a crucial element for the intermediate level of a graduated licensing system. Our objective was to determine whether graduated licensing systems and nighttime curfews reduce motor vehicle crashes, fatalities, or injuries among young drivers.