Buckling Up: Technologies to Increase Seat Belt Use -- Special Report 278 (2004)

Ford Motor Company was the first automobile manufacturer to introduce an enhanced belt reminder system in the United States. Selected Model Year (MY) 2000 passenger vehicles were equipped with a light and chime system that embodies more than the 4- to 8-second light and buzzer system required by the National Highway Traffic Safety Administration (NHTSA). In Europe, development of generic specifications for seat belt reminder systems began in 1995, and belt reminder systems are currently available in several vehicles for sale in the European market.

The effectiveness and acceptability of new enhanced belt reminder systems and other in-vehicle technologies to increase belt use currently being introduced on a voluntary basis by the automobile industry are reviewed in this chapter. The information is drawn from briefings to the study committee by key automobile manufacturers, a literature review, and the results of interviews and focus groups conducted by NHTSA specifically for the present study. The chapter ends with a summary of the state of knowledge.

Ford Motor Company introduced the BeltMinder^™, a registered company trademark, on selected MY 2000 vehicles. By MY 2002, all Ford vehicles were equipped with the enhanced belt reminder for the driver, with a phase-in for the right front-seat passenger starting with MY 2003 vehicles. The BeltMinder complies with the NHTSA regulation for a 4- to 8-second reminder; however, after a pause, the enhanced reminder flashes and chimes intermittently—activating for 6 seconds, then pausing for 30 seconds—for up to 5 minutes if the driver (or passenger) fails to buckle up.

After the introduction of the BeltMinder, NHTSA Administrator Dr. Jeffrey Runge urged other automobile manufacturers to follow Ford’s

lead and provide effective belt reminder systems or other appropriate technologies for increasing belt use.¹ Most of the major manufacturers responded that they were either studying or near to deploying enhanced belt reminder systems, some as early as 2003.² Most plan to introduce driver-side systems first, many at the same time as the introduction of advanced air bags. Front-passenger systems will not appear in significant volumes until MYs 2004 and 2005.³ At the time of the present study, the Ford BeltMinder was the only commercially available system in the U.S. market.

All first-generation enhanced belt reminder systems deployed or under development for the U.S. market use a sequence of light and chime reminders⁴ separated by a pause or a light-only interval from the initial 4- to 8-second “federal” light and chime system (see Box 4-1 for examples of systems). The enhanced systems vary in their loudness, urgency, and duration. They all include a speed or distance trigger, reflecting General Motors’ findings that most drivers fasten their seat belts after the engine is started or when the vehicle is in gear or moving slowly. Only about 30 percent of drivers fasten their belts before starting the engine.⁵

The systems are currently offered for drivers and front-seat occupants, reflecting the availability of front-seat sensors that are or will soon be available on all U.S. vehicles to support the introduction of advanced air bags. The incremental cost of installing the enhanced reminder system is modest.⁶ In contrast, no manufacturer is offering reminder systems for rear-seat occupants. The absence of rear-seat sensors to detect the presence of rear-seat occupants, the complexities of integrating reliable reminder systems with rear child seats and remov-

able backseats, and lower rear-seat occupancy rates currently make rear-seat systems appear relatively costly. For now, the manufacturers are offering systems that indicate to the driver whether rear-seat passengers have failed to put on or have unbuckled their belts during a trip.⁷ All the systems, with the exception of General Motors’ belt reminder, provide mechanisms to disconnect the system, either for a single trip or permanently.⁸

In Europe, the introduction of enhanced belt reminder systems began with a Swedish National Road Authority (SNRA) initiative in 1995. A special working group of researchers, insurance companies, and the automobile industry was formed to develop generic specifications for a seat belt reminder system (Fildes et al. 2002, 3). The specifications took into account some of the shortcomings of the early U.S. interlock systems, which were unable to differentiate between driving and low-speed maneuvers, such as parking or going in reverse. Thus, the new systems activate only after a specified minimum speed has been reached, or after a specified time or distance.

The European specifications have been incorporated in the European New Car Assessment Program (EuroNCAP), a consumer safety information program modeled on NHTSA’s NCAP.⁹ As an incentive to industry, EuroNCAP offers manufacturers up to 3 points out of a total of 37—the difference between a four-star and the top five-star rating of European automobiles—for seat belt reminder systems that meet certain minimum performance criteria (see Box 4-2). In 1999, Saab was the first company to develop a prototype seat belt reminder system that was consistent with the SNRA and subsequently the EuroNCAP reminder system specifications. Today, several vehicles for sale in the European market have belt reminder systems that meet EuroNCAP specifications.

The 1970s experience with interlock systems still influences technology decisions by the automobile manufacturers for the sale of vehicles in the U.S. market. For example, no company is developing an interlock system for sale in the U.S. market as original equipment on vehicles intended for the general public because of concern about potential negative customer reaction. Interlock systems, however, are being developed for special fleets and aftermarket applications. For example, D&D Innovations, Inc., a small manufacturer, is currently marketing an aftermarket device that can be installed in vehicles already equipped with gearshift locks (locks that prohibit a vehicle from being put into gear if the vehicle’s brake is not depressed). The interlock system prevents the vehicle from being put into gear if the driver and passenger are not buckled up at the start of the trip. (Chime and light sequences sound if driver or passenger unbuckles during a trip.) D&D Innovations is targeting the seat belt shifter lock to owners of fleet vehicles as well as to parents of teenage drivers—a high-crash-risk group. In the United States, 16-year-olds have almost 10 times the crash risk of drivers aged 30 to 59, and almost 3 times the risk of older teenage drivers (IIHS and Traffic Injury Research Foundation 2003, 1). D&D Innovations is also working with General Motors so that the shifter lock can be made available as a dealer-installed option. According to D&D Innovations, the cost of the device is less than $200 for aftermarket applications. The cost could be as low as $65 if production volumes were large enough.

Another option for seat belt interlocks involves an interlock system that works with a vehicle’s entertainment systems rather than its gearshifts. For example, if a driver does not respond to a light and chime seat belt reminder that commences when the vehicle is started, the radio or CD player could be made inoperative until the driver or front-seat passenger buckles up. Although an entrepreneur has petitioned NHTSA’s Chief Counsel regarding the legality of an entertainment interlock system he had developed, such a system is not currently being manufactured for sale, either as original equipment or for aftermarket applications.

Development of interlock systems for specific aftermarket applications is not without precedent. For example, the experience with alcohol ignition interlocks has been encouraging. The devices can be effective in reducing impaired driving by convicted offenders. However, in the United States, the practical effectiveness of alcohol interlocks has been limited by their cost and by the small number of offenders willing to install them to drive legally (Voas et al. 2002, 449; DeYoung 2002, 473). North Carolina, Pennsylvania, and California, among other states, have begun to mandate the installation of alcohol interlocks as a prerequisite for DUI offenders to apply for restricted licenses. The effectiveness of seat belt interlocks for high-risk drivers will also likely depend on the extent to which the states and the courts are willing to require their use.

At the second committee meeting in Dearborn, Michigan, four automobile manufacturers—General Motors, DaimlerChrysler, Ford, and Toyota—briefed the committee on the development status of seat belt use technologies and on company studies and market research on the effectiveness and acceptability of the new technologies. The committee also heard from D&D Innovations, Inc. Because the briefings were held in closed sessions to safeguard proprietary information, not all details can be disclosed.

The automobile manufacturers indicated that consumer acceptability is key to the success of new technology introduction, and hence they favor systems that provide a balance between effectiveness and acceptability. Their primary focus is on enhanced belt reminder systems that target part-time users—those who forget to buckle up or who find it uncomfortable or inconvenient on short trips—rather than on more aggressive systems targeting the hard-core nonuser.

The functional characteristics of these reminder systems have already been described in an earlier section. The manufacturers, however, recognized that a number of design decisions were made without the benefit of empirical human performance data, which—if available—might increase both effectiveness and acceptability. For example, the optimal loudness of the reminder’s chime has not been determined, nor has its relation to other in-vehicle warning and information systems, which have been proliferating in recent years. It is well known that human attention and information-processing capacities are limited (Wickens 1991; Kahneman 1973), so the effectiveness of any belt reminder system (and its impact on other aspects of driver performance) must be considered within the context of the overall stimulus and task environment. According to the manufacturers, many such issues, which have not been resolved in the first generation of enhanced belt reminder systems, merit careful study as field evidence accumulates.

The companies were unable to provide systematic field information concerning the effectiveness of the new enhanced belt reminders, which reflects the recent entry of the technologies into the market. In fact, one company suggested that NHTSA should take responsibility for collecting data on the effectiveness of different enhanced belt reminder systems in getting motorists to buckle up, particularly those involved in crashes.

The manufacturers who briefed the committee provided some limited company-sponsored market research on consumer acceptability of

enhanced belt reminder systems. At the December committee meeting, General Motors reported the results of clinics of approximately 1,000 consumers conducted in California in 1999 to gather data on belt use habits and the perceived effectiveness and desirability of current and enhanced belt reminder systems. Forty-nine percent of the respondents reported that the current NHTSA-required 4- to 8-second reminder helps them remember to wear their seat belts. Eighty-one percent indicated interest in an enhanced belt reminder system for the driver and front-seat occupants. Seventy-one percent thought that the systems should be extended to rear-seat occupants, particularly drivers of sport utility vehicles (SUVs) and vans who frequently transport children and find it difficult to see whether their children are buckled up. Yet, only 35 percent reported that they wanted a rear-seat belt reminder system in their next vehicle.

After the December meeting, a January 2001 Ford Motor Company telephone survey of approximately 1,200 owners of Ford passenger cars, SUVs, vans, and pickup trucks—with and without the Ford BeltMinder—was made available to the committee. The purpose of the survey was to obtain customer feedback on the new technology. Ninety percent or more of owners of the Taurus/Sable, Lincoln LS, Ranger, Explorer Sport Trac, Excursion, and Econoline reported that they were completely satisfied with the BeltMinder. Approximately three-quarters of Focus/Cougar, Mustang, and Explorer Sport owners reported being completely or somewhat satisfied with the system (Ford Motor Company and Global Consumer Insights 2001, 5).¹⁰ Eight in 10 BeltMinder owners indicated that they would purchase a vehicle with a belt reminder in the future. More than 7 in 10 would recommend the BeltMinder to other drivers, and almost 90 percent of Ford drivers with the BeltMinder want the system for their passengers (Ford Motor Company and Global Consumer Insights 2001). Female and older drivers (i.e., over 50) scored higher than male or younger drivers on satisfaction with the BeltMinder, interest in buying it again, and recommending it to others.

Only two studies that provide an assessment of the effectiveness and acceptability of enhanced belt reminder systems in the U.S. market could be found in the literature. The lack of studies is not surprising in view of the limited commercial availability of these systems. The first study, conducted by the Insurance Institute for Highway Safety (IIHS) in cooperation with Ford Motor Company, provided an initial evaluation of the Ford BeltMinder and found preliminary evidence that the technology is encouraging increased belt use (Williams et al. 2002). Researchers unobtrusively observed belt use among drivers of vehicles brought in for service at 12 Ford dealerships in Tulsa and Oklahoma City, Oklahoma, in August and September 2001. Overall, seat belt use rates were 76 percent for drivers in vehicles equipped with the BeltMinder compared with 71 percent for drivers of late-model Fords without the reminder system—a statistically significant 7 percent gain (Williams et al. 2002, 295).¹¹ No follow-up studies have been conducted at other locations to determine whether these results can be replicated.

The second study, also conducted by IIHS just before completion of this committee’s work, involved in-person interviews with 405 drivers of Ford vehicles with BeltMinder systems at five Ford dealerships in the metropolitan Boston area in March and April 2003 (Williams and Wells 2003). Ford Motor Company facilitated the study, but it was made clear to potential respondents that the research was being conducted independently. Approximately two-thirds of the 405 drivers interviewed reported that they had experienced the reminder system one or more times when they had neglected to buckle up. Seventy-three percent reported that they buckled up the last time this happened, and 46 percent of all respondents said that their belt use had increased since driving a vehicle with the BeltMinder (Williams and Wells 2003, 6, 10). These positive reports provide further evidence in support of the earlier observational study that the BeltMinder is increasing belt use. The system also appears to be acceptable to drivers. Seventy-eight percent of those interviewed said they liked the system. Seventy-nine percent reported that they would like a similar device in their next vehicle (Williams and Wells 2003, 1).

The responses of the 107 part-time belt users¹²—the primary target group for belt reminder systems—were encouraging. More than four-fifths had encountered the system at least once. Seventy percent had fastened their seat belts in response, and 76 percent reported that their seat belt use had increased since purchasing the vehicle (Williams and Wells 2003, 12). Seventy percent like the reminder system and an equivalent percent would want it in their next vehicle. (The findings concerning acceptability for part-time users were slightly lower than for all respondents, but since the latter include full-time users who are presumably favorably disposed to the reminder system, the results for the part-time users are indeed encouraging.)

Not surprisingly, of the 27 respondents who reported never wearing seat belts or wearing them only occasionally, the vast majority (85 percent) encountered the system more than once. However, only 22 percent fastened their seat belts in response, and only 8 percent reported increased use of seat belts (Williams and Wells 2003, 12). Furthermore, 26 percent disabled the system, suggesting that different technologies or strategies will be needed to get this group of hard-core nonusers to buckle up.

No field studies could be found outside the United States on the effectiveness of enhanced belt reminder systems that meet EuroNCAP specifications. A Swedish study (Bylund and Björnstig 2001) evaluated the effectiveness of older, less aggressive belt reminder systems on Swedish seat belt use rates. On the basis of ambulance personnel data on driver belt use from a population of 477 drivers injured in crashes from 1991 to 1999, the researchers ascertained that only 12 percent of drivers were unbelted in cars with a belt reminder light-and-sound signal, compared with 23 percent in cars without a reminder system, a statistically significant difference (Bylund and Björnstig 2001, 3).

The only other relevant study was a prospective evaluation of the benefits of introducing belt reminder systems in Australia (Fildes et al. 2002), which estimated the potential injury reduction of different belt

reminder system designs, assuming various system effectiveness levels. Using the Monash University–developed HARM model—a method for quantifying injury costs from road trauma—the study examined three belt reminder design options: a simple flashing light and warning tone (similar to the Ford BeltMinder), a slightly more complex system where the flashing light and warning tone increase in intensity at higher speeds, and a complex system where the hazard lights flash after a set period of noncompliance (Fildes et al. 2002, vii). The study assumed effectiveness rates (i.e., increases in belt use rates) of 10 percent for the BeltMinder-like system (slightly higher than the 7 percent belt usage increase found by the IIHS study), 20 percent for the somewhat more complex reminder system, and between 30 and 40 percent for the complex design (Fildes et al. 2002, vii). On the basis of several usage scenarios (i.e., driver only, front-seat occupants, and all occupants), discount rates, fleet life periods, and costs, the model estimated that the benefit–cost ratio was highest for the simplest driver-only belt reminder device. However, the model-estimated benefit–cost ratio was still greater than 1 for the most complex system assuming usage by all occupants, and this system showed the greatest estimated benefits (i.e., reduction in the societal costs of injury) (Fildes et al. 2002, viii).

Interviews conducted in Sweden (Dahlstedt 1999) and focus groups in Australia (Harrison et al. 2000) found that the Saab prototype belt reminder system, with an aggressive light-and-chime system that increases in intensity with speed, would generally be acceptable to drivers who describe themselves as part-time users. For example, of the 500 Swedish drivers interviewed after being observed not wearing their seat belts in traffic, 83 percent said they would buckle up if they rented a car with an aggressive audible warning system (Dahlstedt 1999, 9). When asked if they would buy a car with a gear interlock, 70 percent responded “yes,” and approximately 20 percent said they would choose another car (Dahlstedt 1999, 9).

In November 2000, the Automotive Coalition for Traffic Safety commissioned a nationwide telephone survey (Lawrence Research 2000) of 1,000 licensed drivers in conjunction with a 2001 national summit on

seat belt use. The survey oversampled part-time belt users and hard-core nonusers to determine attitudes toward belt reminder and interlock systems as well as state seat belt use laws.¹³

The survey found that 80 percent of full-time users and 78 percent of part-time users and nonusers reported that the current 4- to 8-second belt reminder system had no effect on their seat belt use behavior (ACTS 2000). When asked their reaction to a law that would require a reminder system that gets louder or brighter, an ignition interlock, or a radio interlock, 53 percent of all respondents and 47 percent of part-time users and nonusers strongly or somewhat favored the reminder system. Of the three options, the reminder system received the least opposition. Only 39 percent of all respondents, and the same percentage of part-time users and nonusers, strongly or somewhat opposed this device (ACTS 2000).

Response to the ignition interlock was polarized. Fifty-four percent of all respondents strongly or somewhat favored the ignition interlock,¹⁴ but 43 percent of all respondents, and 55 percent of part-time users and nonusers, either strongly or somewhat opposed the device (ACTS 2000). The radio interlock received the least favorable rating. Forty-nine percent of all respondents, and 57 percent of part-time users and nonusers, either strongly or somewhat opposed the radio interlock.

Because of limited data on both the effectiveness and the acceptability of new seat belt use technologies, NHTSA conducted in-depth interviews for the present study of potential technology beneficiaries—part-time users and hard-core nonusers—to explore consumer reactions to the technologies. In addition, focus groups of full-time users were conducted to understand their views concerning new technologies, particularly any unintended negative consequences for those who already buckle up. A report detailing the results of this work is available from NHTSA (Bentley et al. 2003); only the highlights are summarized here.

After considering the desirability of various options for assessing the acceptability of different reminder systems, NHTSA concluded that indepth interviews and focus groups would be more useful than a large population survey. Demonstration of the devices with follow-up questions would provide more valid data than asking hypothetical questions to respondents who were unfamiliar with the technologies and had no exposure to them. Limited resources and time constraints of the study restricted the number of in-depth interviews and focus groups that could be carried out.

The interviews were conducted in three locations: Phoenix, Arizona; St. Louis, Missouri; and Portsmouth, New Hampshire. These locations reflect a mix of geographic settings (e.g., urban, rural) and seat belt use laws (Arizona and Missouri are both secondary belt use law states; New Hampshire has no belt use law). The interviews, which were conducted individually and in person, were targeted primarily at self-reported part-time users—the largest nonuser group. A small group of self-reported hard-core nonusers was also recruited. Part-time users were defined as those who claimed to wear a seat belt “sometimes” but had forgotten or neglected to buckle up three times or more in the past month. Hard-core nonusers claimed never to wear a seat belt (Bentley et al. 2003, 9). Participants were limited to those who had purchased a vehicle within the previous 12 months or intended to purchase one within the next year, with the expectation that new or prospective car buyers would be more focused on desired new vehicle characteristics.¹⁵ However, this group may not be representative of the general population. The goal was to recruit 40 participants at each of the three sites. Thirty-two to 35 would be part-time users, and 5 to 8 would be hardcore nonusers. A total of 106 in-depth interviews were conducted at the three sites (Bentley et al. 2003, 10).

In addition to the interviews, four focus groups of 8 to 9 each were conducted at one location—St. Louis—over a 2-day period for a total of

35 respondents (Bentley et al. 2003, 10).¹⁶ Participants for both types of activities were recruited by random digit dialing. No specific attempt was made to represent the demographic characteristics of the areas.

The participants in both the in-depth interviews and the focus groups were exposed to four seat belt use technologies—two belt reminder systems and two interlock systems—reflecting technologies of increasing intrusiveness (see Figure 4-1 and Box 4-3 for system descriptions). The belt reminder systems were presented in the form of two short video clips; the interlock systems were described on two storyboards.¹⁷

Initially, the respondents discussed their opinions about seat belts and the reasons and circumstances affecting their use (see Chapter 2 for results). Then they were asked to rate the technologies, using a five-point scale, on both the effectiveness and the acceptability of each of the four devices.¹⁸ (The order of presentation was rotated in a counterbalancing scheme to prevent order effect bias.) After commenting on each technology, the respondents were asked to rank order the four devices from one to four in terms of their relative effectiveness and acceptability.¹⁹ Finally, the respondents were asked whether the technologies should be mandated (Bentley et al. 2003, 12).

The results of the NHTSA report do not provide quantitative results that can be subjected to meaningful statistical analysis for generalization to the entire automobile-buying population (Bentley et al. 2003, 12). Nevertheless, the findings provide useful qualitative information about consumer reactions to new technologies designed to increase belt use. The results that follow were developed by the committee from the original responses to the interview and focus group questions and do not appear in the NHTSA report.

Figure 4-1 Seat belt use technologies arrayed by level of intrusiveness.

Table 4-1 and the tables in Appendix B provide a summary of respondent ratings of the four technologies’ effectiveness and acceptability. The results are first provided for all 141 respondents.²⁰ Then they are examined by user group (35 full-time users, 89 part-time users, and 17 hard-core nonusers), gender, age, and location (see Table B-1).

Overall Ratings A much higher percentage of the respondents rated each of the technologies “effective” than “not effective” (ranging from

61 to 88 percent). A higher percentage of respondents also rated the two reminder systems (Ford and Saab) “acceptable” than “not acceptable” (71 percent and 56 percent, respectively). However, this result did not hold for the interlock systems, which somewhat more respondents found not acceptable than acceptable (see Table 4-1). Anecdotally, several respondents, generally hard-core nonusers, indicated that the devices were acceptable but not effective because they believed they could circumvent them—for example, by drowning out the sound of the chime with the radio—or disable them entirely (Bentley et al. 2003, 4, 14). These responses obfuscate interpretation of the ratings.

Of the two reminder systems, respondents were more likely to rate the Ford BeltMinder as acceptable (71 percent versus 56 percent for the Saab system) but were also somewhat less likely to rate it effective compared with the more insistent Saab system (78 percent versus 83 percent) (Table 4-1). The transmission interlock was most likely of all the devices to be rated effective—88 percent rated it effective. However, only 43 percent of the respondents rated it acceptable. A somewhat lower percentage of respondents (37 percent) rated the entertainment interlock acceptable. However, 40 percent rated that device as either not effective or neutral (Table 4-1). Follow-up questions found that the effectiveness of the entertainment interlock depended largely on the extent to which drivers use their stereo systems (Bentley et al. 2003, 14).

With the exception of the entertainment interlock, the higher the effectiveness rating for a device, the lower the acceptability rating. This was most pronounced for the transmission interlock—88 percent rated the transmission interlock effective but only 43 percent rated it acceptable.

Ratings by User Group The responses of different user groups, especially part-time users, were of particular interest to the committee because they are the primary group to which the technologies are directed. Nearly two-thirds of part-time users rated the belt reminder systems acceptable (64 percent for the Ford BeltMinder and 60 percent for the Saab system). The reminder systems also were likely to be rated effective (74 percent for the Ford BeltMinder and 84 percent for the Saab system). Approximately twice as many part-time users, however, rated the interlocks unacceptable compared with the reminder systems (Table 4-1). Nevertheless, part-time users were more likely to rate the interlocks as acceptable than other user groups.

Of the much smaller group of 17 hard-core nonusers, fewer were likely to rate the more aggressive technologies—the Saab belt reminder and the transmission interlock—as acceptable compared with the other groups. For example, only 36 percent rated the Saab system acceptable (Table 4-1). And the hard-core nonusers were the most likely of any user group to rate the transmission interlock as unacceptable, with 71 percent rating it not acceptable. Not surprisingly, hard-core nonusers were more likely to give the Saab reminder and the transmission interlock high effectiveness ratings compared with the other two technologies, 70 percent and 77 percent, respectively. The particularly negative reaction to the transmission interlock from hard-core nonusers stemmed in part from their belief that this device infringes on an individual’s right to choose whether to buckle up (Bentley et al. 2003, 15). However, a relatively high percentage (55 percent) of full-time users also rated the transmission interlock not acceptable. This group did not like systems that affect the operability of the vehicle, nor were they sympathetic to the idea of having an intrusive device in their vehicle just because others do not buckle up (Bentley et al. 2003, 34).

Ratings by Gender, Age, and Location Mean ratings are provided by gender, age, and location (Table B-3). Because of small sample sizes, no attempt was made to break down the data further by rating category (e.g., acceptable, neutral, not acceptable) as was done in Table 4-1.

The mean effectiveness and acceptability ratings are higher for females than for males and for the oldest age group than for the youngest age group for all technologies except the entertainment interlock. Males and the two youngest age groups rated the entertainment interlock more effective than did females or the oldest age group, which probably reflects greater use of the stereo system by these groups. However, none of the age groups rated the entertainment interlock very highly on acceptability. Mean acceptability ratings for reminder systems were higher than for interlocks for all three locations. This pattern did not hold for mean effectiveness ratings, mainly because the transmission interlock was rated most effective in all locations.

Mandating Seat Belt Use Technologies Respondents were asked whether they agreed that reminder systems and interlocks should be required in vehicles. If they responded positively, they were then asked whether the federal government should mandate this. Quantitative results were not available for these questions, but a summary of the responses provided in the NHTSA report suggests that most participants were supportive of the idea of mandating seat belt reminder systems and interlocks (Bentley et al. 2003, 38). Although many stated that mandates for reminders were acceptable, some thought that requiring interlocks was not. These devices were considered to be excessive in their attempt to control driver behavior and limit freedom of choice (Bentley et al. 2003, 38). Some hard-core nonusers were against mandates altogether. They believed that wearing a seat belt is a matter of personal choice that should not involve government intervention (Bentley et al. 2003, 15).

Nearly 30 years after NHTSA was prohibited from requiring seat belt interlock systems or continuous buzzer reminders longer than 8 seconds in duration, the automobile manufacturers are voluntarily introducing

enhanced seat belt use technologies in passenger vehicles. Ford Motor Company started the move toward a new generation of enhanced belt reminder systems with the introduction of the Ford BeltMinder on selected MY 2000 vehicles. Enhanced belt reminder systems are also being introduced in Europe, where belt use rates are higher, and incentives are being offered to manufacturers through the EuroNCAP program to improve vehicle consumer safety ratings by providing systems that meet certain performance criteria. No automobile manufacturer, either in the United States or abroad, is providing vehicles with interlock systems as original equipment, targeted to the general consumer. However, a seat belt shifter lock is being developed for special fleets and aftermarket applications in the United States.

Because enhanced seat belt use technologies are so new, few studies of their effectiveness have been conducted. Nevertheless, the available evidence suggests that consumers generally find new belt reminder systems somewhat successful in convincing part-time users—the largest nonuser group—to buckle up. For example, the initial IIHS study (Williams et al. 2002), which was limited to two locations in Oklahoma, observed a statistically significant 7 percent increase in seat belt use by drivers in passenger vehicles equipped with the Ford BeltMinder compared with drivers of nonequipped late-model Fords. A subsequent IIHS study corroborated these findings. In interviews in Boston with drivers of BeltMinder-equipped Ford vehicles, overall, two-thirds reported that they had activated the system. Of these, approximately three-fourths buckled up and nearly half of all respondents said their belt use had increased. Results were encouraging for part-time belt users. More than four-fifths of this user group had activated the system at least once, 70 percent fastened their belts in response, and approximately 75 percent said their belt use had increased. No studies of the effectiveness of new European belt reminder systems could be found.

Information on consumer acceptability of seat belt use technologies from the manufacturers, the recent IIHS study, and the NHTSA interviews and focus groups conducted for the present study suggest a generally positive response to enhanced belt reminder systems. For example, nearly two-thirds of self-reported part-time users rated

reminder systems acceptable in the NHTSA interviews. As a general rule, the more intrusive the system, the less acceptable it is. This finding was particularly pronounced for the transmission interlock, which, of the four technologies, was most likely to be rated effective by all user groups who participated in the NHTSA interviews and focus groups, but was less likely to be rated acceptable across the board than reminder systems.

Self-reported hard-core nonusers who participated in the NHTSA interviews were more likely to be opposed to all systems than other user groups, with the exception of the Ford BeltMinder, which two-thirds of hard-core nonusers found acceptable, as was the case for part-time users. However, as the earlier IIHS study noted, acceptance does not necessarily lead to increased belt use, particularly for hard-core nonusers. More intrusive technologies may be required to convince this group to buckle up.

In sum, the data available to date provide strongly converging evidence in support of both the potential effectiveness and consumer acceptance of many new seat belt use technologies, particularly enhanced belt reminder systems. Despite limitations in the individual studies, surveys, and other pieces of evidence that are spelled out in the present report, the fact that findings from such a diverse set of information sources converge on this core conclusion is extremely important. However, much remains to be learned. Fortunately, larger numbers of belt reminder systems will soon be introduced in the marketplace. With characteristics that vary across manufacturers in the loudness, urgency, and duration of their chime and light components, these systems provide a natural laboratory for study.

Key knowledge gaps remain concerning the design, effectiveness, and acceptability of enhanced belt reminders. For example, unresolved design issues include the optimal loudness of the reminder’s chime and its relation to other warning and information systems. Temporary muting of nonessential systems (e.g., radio, CD player) could be considered so that drivers do not drown out the chime. Appropriate design of disconnection systems is also likely to influence both the effectiveness and the acceptability of belt reminder systems. Finally, because of the benefits of rear-seat belt use, resolution of tech-

nical problems hindering the installation of rear-seat belt reminder systems is important, especially as the cost of sensors for the rear seats declines.

More comprehensive studies of the effects of reminder systems on belt use need to be conducted. Comparative studies of the effectiveness of aggressive belt reminder systems would be helpful in determining whether they can provide additional gains in belt use, particularly among the hard-core nonuser groups.

Finally, more data are needed on consumer acceptance. For example, although initial reactions toward interlock systems were negative, several of their undesirable features (e.g., inability to play the radio when the vehicle is not in motion) could be engineered out. As more consumers actually experience the systems, attitudes may differ from those expressed in interviews, where respondents could only be given general explanations or visual presentations of how the systems work.

The converging evidence of the effectiveness and consumer acceptance of enhanced belt reminder systems is favorable. In the next chapter, potential statutory and regulatory impediments to their installation are addressed.

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IIHS Insurance Institute for Highway Safety

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