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Commercial Motor Vehicle Driver Safety Belt Usage (2005)

Chapter: Chapter 2 - Principal Findings from the Literature Review

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Suggested Citation:"Chapter 2 - Principal Findings from the Literature Review." National Academies of Sciences, Engineering, and Medicine. 2005. Commercial Motor Vehicle Driver Safety Belt Usage. Washington, DC: The National Academies Press. doi: 10.17226/13838.
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Suggested Citation:"Chapter 2 - Principal Findings from the Literature Review." National Academies of Sciences, Engineering, and Medicine. 2005. Commercial Motor Vehicle Driver Safety Belt Usage. Washington, DC: The National Academies Press. doi: 10.17226/13838.
×
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Suggested Citation:"Chapter 2 - Principal Findings from the Literature Review." National Academies of Sciences, Engineering, and Medicine. 2005. Commercial Motor Vehicle Driver Safety Belt Usage. Washington, DC: The National Academies Press. doi: 10.17226/13838.
×
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Suggested Citation:"Chapter 2 - Principal Findings from the Literature Review." National Academies of Sciences, Engineering, and Medicine. 2005. Commercial Motor Vehicle Driver Safety Belt Usage. Washington, DC: The National Academies Press. doi: 10.17226/13838.
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6CHAPTER 2 PRINCIPAL FINDINGS FROM THE LITERATURE REVIEW 2.1 OVERVIEW This chapter presents the principal findings of a review of traffic safety literature on motivational factors relating to CMV driver safety belt use. The review included literature from the United States and other countries. Materials were obtained through a series of online searches of the Trans- portation Research Information System (TRIS) and other internet resources. In addition, this section includes several documents obtained directly from FMCSA that, in some cases, have not been publicly distributed. Sections in this chapter include research on safety belt use by CMV drivers, motivational factors for safety belt usage among CMV drivers and the general driving population, behavior-based safety (BBS) research, safety belt comfort and usability, driver demographics, and the effects of legis- lation on driver behavior. 2.2 GENERAL RESEARCH ON SAFETY BELT USE BY CMV DRIVERS This section highlights three U.S. projects that analyzed usage based on field observations, one synthesis of an Aus- tralian study, and one 5-year study based on data from France. 2.2.1 U.S. Studies on Safety Belt Usage Chapter 3 of this synthesis is based on data collected through structured interviews of truck drivers at truck stops. This method relies heavily on the reliability of driver self- reporting. Direct interaction with CMV drivers is not the only method to measure their behavior. In three U.S. studies, the research team found researchers based their findings on observed behavior rather than on direct collection of data through driver interaction. CMV driver safety belt use was based on whether the shoulder harness was visible to the observer (i.e., if it was visible, the driver was wearing the safety belt). A study of Alaskan safety belt use (Hanna 2003) compared rates of safety belt use among automobile drivers and their pas- sengers with truck drivers and their passengers. In this study, observers measured shoulder harness use on highway and sur- face street locations and found that 83% of car drivers wore their safety belts, while 71% of truck drivers wore theirs. This same study determined passenger use at 67% among truck pas- sengers and 79% among car passengers. It should be noted that most commercial vehicles, especially those that are truckload and not making local deliveries, have only one occupant. Knoblauch et al. (2003) used a similar method to deter- mine the rate of safety belt use among CMV drivers. They conducted a study of Class 7 and 8 trucks at 12 sites for 2-day periods using visual observations of shoulder harnesses as an indicator of safety belt use. Site selection was first determined through a ‘probability proportional to size’ method, which led to the selection of 12 states. Step two determined county groups with more than 300 highway miles within each state, and the third step determined observation locations within those counties. The population size observed, 3,909 trucks, resulted in a reported final safety belt usage rate of 48%. Those vehi- cles hauling trailers with HazMat placards were operated by persons wearing safety belts 67% of the time, drawing a pos- sible correlation between the additional training required to be a HazMat vehicle operator and the attention to safety by the operator. In a recent TRB submittal, Kim and Tremblay (2004) dis- cussed observational research of safety belt use and the dilemma posed by vehicles that had only lap belts. The authors noted that it was legal for commercial vehicles manufac- tured before a certain year to have only a lap belt. In the Kim and Tremblay study, and in studies where safety belt use was observed, it was assumed that if a harness was not seen across the driver, then that driver was not wearing a safety belt. It was then assumed that if a harness was not visible (whether on or off the driver), then the vehicle must have had only a lap belt. Of those drivers who were assumed to have only a lap belt, it was assumed they were wearing their safety belts at the same rates as those who had a visible harness. However, there might have been differences the research did not address, such as perceived safety benefit from the use of a lap belt, increased comfort due to the lack of a shoulder harness, and driver demographics for those who operate older vehicles. 2.2.2 Australian Study In a study that looked at reasons for driver behavior and safety belt effectiveness, Preece (2002) synthesized the results

of several Australian studies that examined the rate at which truck drivers and passengers used safety belts, the reasons that decisions were made to use a safety belt, and the actual value of safety belt use for heavy truck drivers and passen- gers. The research concluded that drivers believed that safety belts were dangerous to use and could be made more com- fortable. Note that these same attitudes were present in the driver interviews. Furthermore, understanding that a need for increased safety belt use among CMV drivers was necessary, the study rec- ommended providing information about the safety benefits of safety belt use to the drivers, encouraging truck owners to equip vehicles with proper safety belt systems, informing drivers of the legal reasons for wearing a safety belt, and finally, increasing enforcement of current safety belt-related regulations. 2.2.3 French Study To understand the relationship between level of injury and safety belt use, accident victims were studied in trauma rooms over a 5-year period in the Rhone region of France (Charbotel 2003). It was found that drivers of trucks were more likely to be seriously injured than their car-driving counterparts. The research found a statistical ratio of 1.87 for truck operators receiving severe injuries, compared with automobile drivers, in similar crashes. Researchers placed blame for this higher rate and scope of injury on the lack of safety belt use by truck drivers. The research thus highlights the problem of low use rates of safety belts among truck drivers and the potential harm of not wearing a safety belt when driving a truck. 2.3 DRIVER MOTIVATIONAL FACTORS AND INCENTIVES FOR SAFETY BELT USE The provision of incentives for both private and CMV driv- ers to wear safety belts has been studied extensively, and the research has found that those who chose to wear their safety belts did so for a number of reasons. As documented in Chap- ter 5, safety, laws, and family all played a role in why users chose to wear a safety belt regularly. But when drivers were partial users or strong non-users, the latter reasons did not appear to play a role in increasing safety practices such as safety belt usage. Incentives, however, have been shown to, at the very least, influence drivers in the short term to wear safety belts. Geller, Paterson, and Talbott (1982) described a situation where college staff, students, and faculty were offered con- tingent and non-contingent rewards for safety belt use and found that only those rewards that were contingent on safety belt use significantly impacted behavior, though both rewards had a message regarding the use of safety belts. Thus, it appears to be important that safety belt use relate directly to the incen- tive for the practice to be effective. 7 A similar study by Geller (Dec. 1982) offered employees of a munitions plant an opportunity to win a prize contingent on safety belt use. Geller found that safety belt use more than doubled during the incentive treatment, but fell back to pre- vious levels during a follow-up. These two studies appear to indicate that quick, one-time incentives do not contribute to long-term safety belt use. In a series of case studies and recommendations, Geller (Oct. 1982) described incentive types for use by employers with a goal of influencing safety belt use among employees. An emphasis was placed on incentives, rather than disincen- tives, with discussion of incentive types including direct and immediate rewards, direct and delayed rewards, and indirect rewards. The long-term effects of employer programs designed to increase safety belt use were explored in Geller et al. (1987). They reviewed 28 different programs at nine separate occu- pational settings that targeted safety belt use. Four categories were determined within the nine settings: those that offered direct and immediate rewards, those with direct and delayed rewards, those with indirect and delayed rewards, and those that offered no rewards. Several conclusions were drawn: • Amount of participant involvement elicited by the intervention. Smaller discussion groups elicited more participation per participant. Thus, try to keep discus- sion groups fairly small to elicit more active driver involvement. • Degree of social support promoted by the interven- tion. Social support was usually affected by the degree of active peer, friend, and family involvement. If possible, try to involve family members and coworkers as much as possible; they can be a valuable source of motivation and support. • Amount of specific response information transmit- ted by the intervention. In other words, be specific and explain intervention components and new behavioral knowledge clearly and carefully. • Degree of extrinsic control exerted by the interven- tions (i.e., incentives and disincentives). Try to man- age the use of incentives and disincentives and only use them if other approaches have failed. • Individual’s perception of autonomy or self-control regarding the behavior change procedures. Auton- omy was increased by the perception of intrinsic control and freedom of choice. Thus, allowing employees to choose their own safety-related goals and other inter- vention components will increase feelings of empower- ment and self-control. More recently, the effects of incentives tools as a motiva- tional factor in increasing safety belt use was explored by Hagenzieker, Bijleveld, and Davidse (1997). The study team conducted a meta-analysis of research publications regarding the use of incentives for safety belt use. Two coders

analyzed a total of 139 articles each (this includes duplicate articles) during their research. The final synthesis of these articles resulted in a differentiation between the short- and long-term effects of incentive tools. As might be expected, there were found to be substantial increases in usage of safety belts during the immediate time after an incentive was offered and/or received. Long-term effects, however, did not show the same results. During follow-up surveys of incentive pro- grams, there was still found to be an overall increase in safety belt use from the use rates before the incentive program. Finally, Herbal and Skopatz discuss the literature of and practices for motivating safety belt use. More specifically, their research focused on two areas, the first was an exami- nation of employer influence on employee safety behavior (regardless of regulatory efforts), and the second was a review of programs produced to help employers increase safety among their employees. They concluded that there were many motivating factors that could be used to compel employees to use safety belts, but none stood out as the ‘best practice’ method. 2.4 BEHAVIOR-BASED SAFETY Assuming that safety belt use can help prevent death and reduce the severity of injuries that result during crashes, the lit- erature on safety practices suggests that BBS practices offer a workplace an approach to positively reinforce desired behav- ior. A detailed discussion of BBS in a commercial vehicle safety setting can be found in CTBSSP Synthesis 1 (Knipling, Hickman, and Bergoffen 2003). White and Washington (2001) found that enforcement intensity was positively correlated with safety belt use. When enforcement covered a greater area however (lane miles of enforcement coverage) safety belt use declined. Safety belt use was also higher in urban areas than in rural areas. These findings were consistent with the other research that indicated that safety belt use for strong non-users was reduced when drivers did not think they were being observed or their risk of ‘being caught’ is lower. It should be noted that a desire for greater enforcement was indicated as something that would increase safety belt use by CMV drivers who were inter- viewed by this research team. A study of taxicab drivers, who are often exempt from safety belt laws, found that use rates were typically lower for these drivers than for the general population. When strong laws that did apply to them were put into place, safety belt use increased dramatically among cab drivers. The study suggests that a ‘punishment’/disincentive may be very effective in increasing safety belt use, where fear of losing a license may be the nec- essary incentive to use safety belts (Ferguson et al. 1999). Other studies have found that while any type of program had some effect on increasing safety belt use rates, law and incentive programs produced the highest increase in use (Johnston, Hendricks, and Fike 1994). This again supports 8 the work done by Geller and others indicating that incentives and stronger enforcement techniques are most effective. Research conducted by Boyce and Geller (1999) on what is termed a multiple intervention level (MIL) hierarchy found that there was a modest increase in safety belt use with the promise-card commitment strategy (a driver signs a card com- mitting to future safety belt use) combined with an incentive/ rewards strategy. The study overall indicated that repeated attempts to change behavior using similar interventions (those with the same level of intrusiveness) were not as effective at changing behavior which was unaffected by the first applica- tion of the intervention. It is therefore necessary to progres- sively use more intrusive interventions if the initial attempts are not effective. Some recent research in the United States (Shults et al. 2004) has indicated that states that directly enacted primary laws (in which the driver is penalized for non-use) demon- strated more safety belt use than those that relied on sec- ondary laws (in which the driver can only be penalized for non-use after a moving violation is witnessed). International studies have found that when individuals were personally prompted to wear safety belts they were more likely to do so than when more methods, other than personally focused methods, were used (Gras et al. 2003). Studies con- ducted in Greece indicated that similar issues manifested them- selves when the non-use of safety belts was studied. In particular, the study by Chliaoutakis et al. (2000) found that while legal requirements increased safety belt use, discomfort and miles traveled reduced safety belt use. A study of incentive programs and enforcement on mili- tary bases in the Netherlands found that enforcement was a more accepted countermeasure than rewarding drivers for safety belt use. However, the caveat is that participants who were receiving the incentive treatment had a more positive opinion of this program than those who were exposed to the enforcement treatment (Hagenzieker 1992). A research study in Canada found that safety belt non-use was most common among drivers who (1) were younger and male, (2) had high-risk health habits (e.g., drinking and driv- ing), (3) were speeding, (4) were smoking, (5) were living in rural regions, and (6) had lower education levels (Sahai et al. 1998). 2.5 RESEARCH ON SAFETY BELT COMFORT AND USABILITY The literature indicated that discomfort was one reason some CMV drivers did not wear safety belts. Specific rea- sons included harness belt rubbing (especially when com- plicated by vibrations), tightness or looseness, and lack of mobility. Though many drivers indicated that the effective- ness of the safety belt would be decreased if changes were made, there was still a desire for a system that had greater levels of comfort.

In one study, an attempt was made to improve seat design methods and processes and to capture the effects of seat dyna- mics on ride quality. Hix, Ziemba, and Schoof (2000) sug- gested that since air suspension seats used in trucks isolated a significant amount of the road vibration, it was critical the seats be designed so that the driver experienced a good ride from the seat. Hix et al. evaluated two different seats: (1) a typical North American air-ride seat which had thick-soft foam, a parallelogram vertical suspension, and a pendulum type fore/aft isolator and (2) a typical European seat which had thin-firm foam, a scissor-type vertical suspension, and a spring-type fore/aft isolator. To accomplish a thorough modeling of truck seats, Hix et al. accounted for numerous measurements of several obvious seat components (seat cushions, riser base, air springs, shocks, shock absorbers, fore-aft isolators, nuts, bolts, bearings, etc.) and of a number of seat design features (including vertical per- formance and fore/aft compliance). As part of their project, Hix et al. also chose to evaluate safety belt comfort. They did their physical tests on a 5-degree of freedom seat-shaker table, upon which they measured such characteristics of seats as accelerations, displacements, forces such as force-deflection splines (stiffness), and constant damping coefficients (for vibration attenuation). Hix et al. intended that the forces measured validate com- fort variables of the full occupant restraint systems (safety belts). However, their work in taking measurements of both seats found the forces to be small; and the safety belt retrac- tors they tested never experienced “lock-up.” They con- cluded the safety belts did not have any adverse effects on comfort during any of their normal test ride (shaker table) events. Therefore, Hix et al.’s seat models did not include the entire restraint system, including the retractors (Hix et al. 2000). In 2001, Balci, Vertz, and Shen conducted a questionnaire survey regarding safety belt comfort and usability. Signifi- cant findings in this survey indicated that five problems were persistent among automobile drivers. This research showed first that two of these issues were (1) that the safety belt was difficult to negotiate with clothes and (2) that the belt would get caught in the door. These were not found to be common complaints among those CMV drivers who answered the research team’s questionnaire. Three other complaints, belt twisting, belt lock-up, and difficulty locating the buckle, were 9 as common to this research project as they were to the Balci study. 2.6 DRIVER DEMOGRAPHICS A self-reported data study focusing on potential impacts of driver demographic characteristics (Shinar, Schechtman, and Compton 2001) found through its analysis that observing speed limits, not drinking and driving, and wearing a safety belt were safety behaviors that were entirely independent of one another. Furthermore, the study found—contrary to certain stereotypes—that income, education, and age were not deter- minants of safety behaviors. The only predictor found was that female drivers are more likely to follow all three safety com- ponents of this study. 2.7 EFFECT OF LAWS Cohen and Einar (2001) concluded that safety belt laws applying to all drivers did lead to an increase in safety belt usage, and thus an increase in lives saved. It also drew a com- parison between primary and secondary state safety belt laws. The researchers concluded through their analysis that if all states moved toward a primary enforcement policy, national rates of safety belt use would increase 9% to 77% and 500 lives would be saved annually. 2.8 OVERVIEW OF AUTO SAFETY BELT PROGRAM The research team also considered the significance of the efforts and success of the NHTSA’s earlier initiative to increase safety belt use by automobile drivers. Although fac- tors relating to safety belt use by CMV and passenger car driv- ers are different in some respects, the information about the NHTSA effort can provide a baseline and starting point for future efforts to promote increased CMV driver safety belt use. A detailed report of the NHTSA program is included as Appendix E of this synthesis. It outlines the phases and pro- grams associated with increases in safety belt use from 1978 to 2003. The appendix describes the approaches used to increase safety belt use, including public information, education, incen- tives and rewards, requirements (laws), and enforcement.

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TRB’s Commercial Truck and Bus Safety Synthesis Program (CTBSSP) Synthesis 8: Commercial Motor Vehicle Driver Safety Belt Usage identifies and documents motivating factors that influence commercial motor vehicle (CMV) drivers in deciding whether to wear safety belts and research and practices that address CMV safety belt usage. It also offers a review of ergonomic and human engineering factors in the design and use of safety belts in CMVs as well as approaches to facilitate safety belt use by truck manufacturers.

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