Motor vehicle crashes are the leading cause of injury and death among US teenagers, and teen drivers have crash rates higher than any other age group [1–3]. Teen driver crashes also cause serious injuries and fatalities to other occupants: approximately 30% of fatal crashes that involve a teen driver lead to death or serious injury to occupants of other vehicles involved in the crash [2]. Compared with adult drivers, a higher percentage of teen fatal crashes involve driver error [4]. Crash rates among novice drivers are highest during the first months of unsupervised driving, and interventions to increase safe teen driving may be most effective if they affect early driving experiences [5, 6].

Existing studies indicate that parents have varying levels of engagement in helping their children mature to independent drivers, and they face challenges in knowing exactly how to best influence safe driving behaviors [7, 8]. Although studies have found that parents and teens believed supervised driving was important, more than a quarter of parents spent less than 25 total hours driving with their teen [9, 10]. Furthermore, parents spent most of their supervised driving time in the daylight, on residential roads, and in light traffic -- the least challenging driving environment -- and did not supervise driving in more challenging environments over time [11].

Studies have found that parents generally exhibit poor monitoring and control of risky driving behaviors. Conversations about driving focus more on basic vehicle operations (e.g. changing a tire) and defined rules (such as when the teen can use the car and when to be home) rather than conversations that set expectations and motivate teens to act safely (e.g. wearing their seat belts or avoiding distractions) [12–14]. Studies have found that when safety was discussed, topics were very general, such as instructing teens to “know the rules of the road.” Yang et al. found that teens who reported that their parents talked about safety had more safety-prone attitudes, but what parents themselves reported talking about was not related to safety attitudes – indicating that it is not so much what the parent says but what the teen actually hears that influences safety attitudes [15]. This limited evidence clearly indicates that the quantity and quality of conversations as well as the topics addressed are all critical in influencing safe driving behavior.

Studies of parenting behavior show that good parenting practice can have profound effects on adolescent development and are strongly tied to reduced risk-taking behaviors [16–18]. A recent study has suggested that parenting skills can be successfully taught to and implemented by parents and caregivers [7]. Based on this growing evidence, the Community Preventive Services Task Force has recommended parent/caregiver interventions that use person-to-person techniques to improve parenting skills as an evidence-based approach [19].

We present results from a randomized controlled trial of an intervention called Steering Teens Safe that taught parents communication strategies to encourage safe driving. The intervention group was compared to a control group to measure teen-reported quantity and quality of safe driving communication and self-reported risky driving behaviors.

Baseline demographic characteristics did not differ significantly by intervention status, indicating that randomization was successful (Table  1). Over 80% of the parents were mothers, while sex of the participating teen was evenly divided between males and females. Father/daughter dyads were the least common dyad combination. The majority of parents were in their 40’s, married, and two-thirds were college graduates. The majority of participating teens were 15, as older teens were only eligible if they had delayed licensure. Over two-thirds began supervised driving at age 14 (which is the youngest age of legal supervised driving in Iowa), although 17.9% of intervention teens and 23.9% of control teens started driving younger than age 14. More than 70% of teens reported driving 6 or more days a week at the beginning of the study.Table 1

Demographic characteristics for parent/teen dyads by intervention status

As the first step in evaluating the intervention, we compared the quantity and quality of conversations about safe driving as reported by intervention and control teens (Table  2). Avoiding distractions when driving was the most frequently addressed topic for both intervention and control teens; driving in bad weather, wearing a seat belt, and maintaining a safe speed were also among the most frequently addressed topics. Driving on rural roads, including 2-lane roads, gravel roads, uncontrolled intersections, and sharing the road with farm equipment were the least frequently addressed topics, although these were more frequently discussed by intervention parents. Although the average Talking Topics Score, which is the sum of the scores for individual topics, was higher for the intervention group, this difference was not statistically significant. The mean overall success score, ranked from one through ten, was significantly higher for intervention (7.97) than for control teens (7.32, p = 0.035).Table 2

Teen-reported talking topics score and talking success score

We next evaluated the intervention by comparing teen-reported risky driving behavior by intervention status. Intervention teens had lower mean Risky Driving Scores than control teens at both one (4.49 for intervention; 5.68 for control) and six months (6.26 for intervention; 7.91 for control) (Table  3). Risky driving scores generally increased from one to six months. Intervention and control teens were first compared without regard to the success of the intervention. The generalized linear model indicated that the intervention was associated with a 21% lower mean Risky Driving Score (Estimated mean ratio = 0.79, 95% CI = 0.55, 1.15). The intent-to-treat mean ratio was significant based on the 85% interval (0.60, 0.99).Table 3

Intervention effects on risky driving mean scores for teens, by treatment group

We next examined the effects of the intervention on teen risky driving considering the Talking Topics Score, assuming that both parent communication success and the intervention could influence risky driving. We hypothesized that parents who participated in the intervention and who had more success in communication would have teens with lower risky driving. Compared with control teens with low Safe Driving Topics Scores, intervention teens who had high Safe Driving Topics Scores had a 42% lower Risky Driving Score (95% CI = 0.36, 0.94). Intervention teens who reported low Talking Topics Scores had a 31% lower Risky Driving Score compared with control teens with low scores, but this difference was not statistically significant at even the 0.15 level. Among the control teens, those whose parents had high Talking Topics Scores had a 24% lower Risky Driving Score than those whose parents had a low Talking Topics Score (not significant). Intervention groups with both low and high Talking Topics Scores had lower risky driving scores compared with the control group with a low Talking Topics Score.

Intervention teens who reported a high Talking Success Score had a 44% lower Risky Driving Score (90% CI 0.32, 0.98) when compared with control teens who reported a low Talking Success Score. Control teens who reported a high Talking Success Score had a similar effect as intervention teens, showing a 46% lower Risky Driving Score than control teens who reported a low Talking Success Score. Intervention teens who reported a low Talking Success Score had a 12% higher Risky Driving Score (90% CI 0.68, 1.88). However, only five intervention teens had a low Talking Success Score.

This research contributes to the small but growing body of evidence that parents can positively influence their teen’s driving behavior, and that this influence can persist even after their teen begins to drive unsupervised. Differences between the overall intervention and control groups were marginally significant. However, intervention teens had lower Risky Driving Scores regardless of whether or not the teen reported parent communication scores as high or low. Intervention teens who reported that their parents had high communication scores had the lowest risky driving scores with a 42% reduction (95% CI 0.36, 0.94). Among control teens, those who reported high communication scores had lower risky driving than control teens who reported their parents had low communication scores. These findings indicate that risky driving behavior was successfully reduced among teens whose parents participated in the intervention or were successful communicators.

Our findings indicate that Steering Teens Safe is not likely to have extremely large effects, but the program does have a high probability of having a positive effect. The approach used in Steering Teens Safe may hold the greatest promise in augmenting other strategies to reduce teen driver crashes, in particular those directly focused on the teen. Graduated Driving Licensure laws have been effective in reducing teen driver crashes by limiting driving in the highest-risk situations (such as late-night driving and driving with other teen passengers) during the early phases of licensure. Strong evidence from more than a decade of research estimates that GDL has reduced teen driving injury and fatal crashes by 20 – 40% [27–30]. Recognizing that the elements of GDL laws vary between states and that effectiveness will be moderated by the level of adherence, programs such as Checkpoints have been developed to assist parents in setting driving rules, restrictions, and expectations [31–33]. In particular, parents participating in the Checkpoints program had implemented more restrictions on late-night driving, teen passengers, and high-speed roadways than control parents [34].

These programs have focused primarily on rules and restrictions so that teens begin driving in low-risk environments. Developing safe driving behaviors is difficult to address solely through driving restrictions, especially when teens begin to drive without supervision. Some risk-taking is a normal part of adolescent development, and once teenagers begin to drive unsupervised, they could choose unsafe driving behaviors, such as not using their seat belts, to rebel against restrictions on driving [7, 35]. Furthermore, restrictions are more likely to be followed by teens if they are communicated to them effectively by parents [15]. Thus, approaches that combine restrictions and self-motivation with effective communication are likely to be the most effective.

Research on parenting and teen risk behavior supports this combination. For example, one study found that parent communication alone was not associated with reduced youth substance use, but communication in combination with parental monitoring was [36]. Studies of healthy eating have found that food rules and restrictions are associated with overeating and eating without hunger, but strong parent–child communication bonds are associated with good eating behaviors [37]. Steering Teens Safe focused exclusively on communication strategies between parents and teens and did not integrate rules and restrictions. Future research will integrate these facets into Steering Teens Safe.

Enrollment goals for this study were not met. Recruitment was challenging because we enrolled only parent/teen dyads who both agreed to consent, and because our Human Subject Protection Office required a passive recruitment strategy. Although our enrollment goals were not met, loss to follow-up was very low (15.6% for intervention and 6.3% for control). Because our target sample was not met, we examined multiple confidence limits for the overall program. All of the confidence intervals showed consistent and high precision with the ratio of the upper to lower confidence limits ranging from 1.7 to 2.1. Additionally, the majority of the confidence limits were within the range of showing program effectiveness at all of the different alpha levels examined. For example, although the main effect estimate (0.79) was not significant at an alpha level of 0.05, the confidence limit of 0.55 to 1.15 shows only a small proportion of the limit above the null value of 1.00.

We want to comment on this approach, as we notice increasing reliance on the arbitrary choice of an alpha level of 0.05 for most epidemiological analyses. Interpreting findings based on multiple confidence levels and the interval level of consistency and precision demonstrates the alpha level at which these data meet the general criteria of statistical significance, and examination of confidence limits provides information about the consistency and precision of the estimates. This approach shows that our findings are significant with a lower level of certainty, yet does not diminish their practical importance. With the dearth of parent tools to encourage safe teen driving and research that shows a clear need for such tools [9], interventions that show success with 90% and 85% confidence intervals that are consistent and precise among relatively small sample sizes show some promise.

This study has several additional limitations. Outcomes were self-reported. Teen reports of communication quality and quantity were used instead of parents so that we could measure the intervention as it was received by teens. However, self-report measures of both communication and risky driving could be biased in either direction. A conservative bias could have occurred if teens in the intervention group were more aware of their risky driving behaviors and thus reported more of them. Alternatively, teens in the intervention group may have been more likely to report better communication and reduced risky driving because they perceived those as the desired responses. Future research will integrate more objective outcome measures.

Based on previously published findings that parents rated this intervention highly and that parents were successful in engaging in the intervention techniques, and with the findings here that suggest a relationship with reduced risky driving behavior, we recommend further development of interventions that increase parent’s quantity and quality of safe driving communication with their teens.