Safety Belts, Airbags, and Child Restraints Special Report 224 (1989) / Chapter Skim
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1989 TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE Chairman Louis J GAMBACCINI, General Manager, Southeastern Pennsylvania Transportation Authority (SEPTA)
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SPECIAL. REPORT 224 SAFETY BELTS AIRBAGS AND CHILD RESTRAINTS Research To Address Emerging.
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Transportation Research Board Special Report 224 mode I highway transportation subject areas 51 transportation safety 52 human factors 53 vehicle characteristics Transportation Research Board publications are available by ordering directly from TRB. They may also be obtained on a regular basis through organizational or individual affiliation with TRB; affiliates or library subscribers are eligible for substantial discounts.
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Study Committee To Identify Research Needs for Occupant Restraints MARY BETH BERKOFF, Chairman, Burson-Marsteller, Chicago, Illinois WAYNE ANDERSEN, Circuit Court, Chicago, Illinois THOMAS E BRYER, Pennsylvania Department of Transportation, Harrisburg THOMAS CARR, Motor Vehicle Manufacturers Association of the United States, Detroit, Michigan FORREST M
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Preface Since the passage of the 1966 federal requirement that lap-shoulder belts be standard equipment for all front outboard seating positions in passenger cars, there has been an ongoing process of study, rule making, and litigation concerning the occupant protection performance standard set in Federal Motor Vehicle Safety Standard (FMVSS)
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evaluation would be timely and to identify pending and emerging policy issues, review current research, and recommend additional research to answer emerging policy questions. Occupant restraints, a subset and fundamental element of occupant protection, are the focus of this project.
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Contents Executive Summary . 1 1 Introduction ..........................................7 2 Mandatory Safety Belt Use Laws .........................
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Executive Summary LTHOUGH MANY POLICY DECISIONS regarding occupant re- Jft straints have been made -- the passive restraint requirements of Federal Motor Vehicle Safety Standard 208 (FMVSS 208) are being phased in, and most states- now have mandatory safety belt use laws -- important policy questions remain.
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SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS ation proves these laws to be effective, they will be repealed. Early evaluations of state mandatory use laws indicate that more than 1,000 lives are being saved annually.
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Executive Summary males with less than a high school education and of a lower SES are the least likely to wear belts, but they are the most likely to be involved in crashes. Research should be conducted to identify high-risk groups of nonusers, determine why they do not use safety belts, and evaluate alternate methods for changing their behavior.
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4 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS performance standard in which the manufacturers would have to certify that a high proportion of a test user group would properly install the child seat in a sample of vehicles. The feasibility of this approach should be evaluated.
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Executive Summary The current test dummies, although substantially improved over earlier versions, do not measure soft tissue damage to the abdomen or brain and cannot measure damage to the spine or spinal cord. These dummies can measure loadings to the neck, but the interpretation of the loading in terms of injury outcomes is uncertain.
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1 Introduction P UBLIC POLICY MAKING on occupant restraints in the United States has reached a crossroads. After decades of tortuous legal and political maneuvering (Graham 1989; Tolchin 1984)
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SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS In the majority of the states that have mandatory use laws, half or more of occupants ignore the law. Two states have repealed mandatory use laws, another canceled its law before it took effect, and others have mandatory sunset pmvisions.
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Introduction 9 tural improvements interact with occupant restraints. These issues, however, are beyond the scope of this pilot effort.
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2 Mandatory Safety Belt Use Laws S INCE 1984, when New York passed the first mandatory safety belt use law, 37 states and the District of Columbia have enacted such legislation. Research estimating the effectiveness of these laws in reducing deaths and injuries is important at both the federal and state levels.
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12 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS STATE LEGISLATION Mandatory safety belt use laws are quite common in most industrialized nations and have been for some time. Czechoslovakia enacted the first national mandatory use law in 1969 and was followed shortly thereafter by the Australian states and New Zealand (Grimm 1988)
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Mandatory Safety Belt Use Laws13 quently switched their position. The law was repealed by a 53 to 47 percent vote.
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TABLE 1 STUDIES OF EFFECTIVENESS OF STATE MANDATORY SEAT BELT USE LAWS Author (year)
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Mandatory Safety Belt Use Laws 15 section. These data, a census of fatalities, are from the Fatal Accident Reporting System (FARS)
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16 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS The effectiveness of mandatory safety belt use laws in the United States, when estimated with time series models, has not matched effectiveness estimates made on the basis of the research that predicts the effectiveness of safety belts in reducing fatalities and injuries in individual crashes (see Chapter 4)
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Mandatory Safety Belt Use LA2ws 17 effect of selective recruitment on overall effectiveness is not large (roughly 4 to 5 percentage points)
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18 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS selective recruitment, and overreporting of belt use in crashes have the most empirical basis (Campbell and Campbell 1988; Hunter et al.
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Mandatory Safety Belt Use Laws 19 has the additional advantage of incorporating estimates of belt usage, as opposed to using a dummy variable to account for the presence or absence of a belt use law (as in the time series models)
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20 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS REFERENCES Adams, J
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Mandatory Safety Belt Use Laws 21 Latimer, E., and L
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1 Methods for Increasing Restraint Use F OR THOSE STATES with mandatory safety belt use laws in effect and for those without use laws, the most pressing policy implementation question is how to increase belt use. After an examination of public opinion data and surveys that identify the users and nonusers of belts, research that evaluates methods for increasing safety belt use is reviewed in this chapter.
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24 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS reason, 13 percent did not believe that belts were effective, and 11 percent said that belts were uncomfortable or inconvenient. A survey in Massa- chusetts reported that voters who switched from supporting to not supporting the state's belt use law gave the invasion of personal freedom and the belief that the laws were ineffective as the main reasons (Hingson et al.
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Methods for Increasing Restraint Use 25 (1986) support the finding that drinking drivers are less likely to wear belts.
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26 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS reductions in the fatality rates in primary enforcement states than in secondary enforcement states (about 2 percentage points)
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Methods for Increasing Restraint Use 27 problem may be due to lack of support by police. It appears that after funding for special enforcement is withdrawn, police attention and priority shift to other concerns.
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28 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS emphasizing the primacy of external rewards, programs with no rewards, which rely on gaining commitment through group process discussion, had the highest initial increases and the longest sustained effects. Whether these experiences with programs in small companies can be applied to large corporations or institutions is not known.
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Methods for Increasing Restraint Use 29 Information has the greatest effect when it is tailored to the specific needs of a specific audience. Audiences seldom change their behavior in response to information that they already have.
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30 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS A substantial proportion of nonwearers are in demographic groups associated with support for restraint use; that is, they have more than a high school education, are 30 years of age or older, and are of higher SES. The group least likely to wear belts consists of young males with less education and lower SES.
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Methods for Increasing Restraint Use 31 Some research indicates that nonusers are sensitive to the level of the fine, but more research is needed to determine whether the perceived level of the fine is as important as the perceived threat of being stopped at all. Fear of a large fine, for example, may diminish as drivers recognize the low probability of being stopped for violating the law and discover the low level of most fines.
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32 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS Geller, E
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Methods for Increasing Restraint Use 33 Wagenaar, A
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IR Alternate Occupant Restraint Designs V IRTUALLY ALL AUTOMOBILES currently in use have man-ual lap-shoulder belts, and a growing number have automatic restraints. The emerging issue to be considered in federal regulatoiy policy is how to optimize passenger protection while simultaneously accounting for both the performance of the alternative systems in the marketplace and the likelihood that motorists will use them.
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36 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS shoulder belt effectiveness in reducing fatalities is closer to 40-50 percent (Evans 1986a, Partyka 1988a)
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Alternate Occupant Restraint Designs37 While the debate raged over the effectiveness of airbags, product development continued, and several thousand vehicles were outfitted with airbags during the 1970s. The experience with these vehicles and with models outfitted with airbags in recent years has been promising and has proved that popular misconceptions about airbags are untrue.
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38 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS sponsored crash tests that used anesthetized animals to simulate the risk to out-of-position children demonstrated that occupants seated immediately adjacent to an airbag that deploys in a crash can receive serious and lifethreatening injuries (Mertz et al.
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UPPER ANC HO RAG NTERLOC K ••• _; BOLSTER :: EE EMERGENCY RELEASE SHOULDER BELT LAP BELT RETRACTOR ENERGY ABSORBING BUCKLE -' END WITH IGNITION INTERLOCK AUTOUATC 2 POINT RESTRAINT CIRCUIT BREAKER GUIDE RAiL EMERGENCY LOCK IT ITCH DR LOCK SWITCH TOR ERGENCY-LOCKING rRAcT0R ASSEMBLY THIN COVER) MOTORIZED AUTOMATIC 2 POINT RESTRAINT DOOR UPPER FRAME SHOULDER BELT ANCHOR BUCKLE EMERGENCY - RaEASE WITH SWITCH INBOARD TUNNEL MOUNTED RETRACTOR WITH TENSION RELIEVER AUTOUAT1C 3 POINT RESTRAINT FIGURE 1 Automatic belt designs (from Johannessen 1987)
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40 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS denying these estimates, however, are limited. Nash, for example, derives his estimate of the performance of automatic versus manual belts from only two vehicle models.
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Alternate Occupant Restraint Designs 41 release, NHTSA announced that it would approve its proposed rule requiring lap-shoulder belts in all outboard seating positions for new vehicles (53 ER.
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42 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS provision of adjustable mountings might overcome the tendency of drivers to increase the slack in the shoulder belt to reduce rubbing against the neck or chest. NTSB and others have noted that excessive slack reduces the benefits of shoulder belts (NTSB 1988; Ciccone and Wells 1987)
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Alternate Occupant Restraint Designs 43 problems for occupant restraints. Research is needed to determine the optimum restraint design for smaller vehicles.
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44 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS Even though misuse of child restraints is decreasing, it continues to undercut the performance of these systems. Design improvements offer one approach to overcoming misuse.
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Alternate Occupant Restraint Designs 45 for evaluating the effectiveness of restraint systems. Although the benefits of such devices would not be realized for some time, more reliable information about restraint use must be developed.
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46 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS Evans, L 1988 (September)
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Alternate Occupant Restraint Designs 47 Shoulder Belts in Passenger Vehicles Under 10,001 GVWR. Docket 87-08-No1-001.
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AV i .-~ 4lat, dill
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Medical and Biomechanical Aspects A INCREASING NUMBERS OF OCCUPANTS become pro- tected by the current generation of restraints, policy issues will shift from providing restraints to optimizing their crash performance. Federal research policy should place greater emphasis on funding the basic research that will be needed to produce the next generation of design for protection against injury.
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50 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS et al. 1988, Gennarelli 1987, Dreghorn 1985, Dooley 1987)
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Medical and Biomechanical Aspects 51 Abdominal Injury Fatalities caused by ruptures of the spleen and liver are decreased by proper lap-shoulder use by vehicle occupants (Rutherford 1985)
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52 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS injuries than do studies based on police reports. Clinical studies can indicate issues and potential problems, such as the apparent tendency of lapshoulder belts to cause minor neck injuries.
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Medical and Biomechanical Aspects 53 enormously in their tolerance to brain injury, fracture, and damage to major organs. The numbers of the most vulnerable sector of the population, the elderly, are increasing the most rapidly, and this group is the least protected by current standards.
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54 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS uniform data-reporting forms (perhaps an improved Centers for Disease Control trauma registry) , more training in their use, and greater cooperation among the different agencies that are collecting information is needed.
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Medical and Biomechanical Aspects 55 Harms, P., et al. 1988 (November)
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Economic Considerations J N ADDITION TO DISCUSSIONS about the effectiveness of various occupant restraint policies, a considerable amount of debate has taken place about the benefits and costs of these policies. This topic continues to be relevant as the U.S.
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58 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS willingness-to-pay approach as a basis, Mannering and Winston estimate that motorists are willing to pay $5,250 for the safety benefit of belts. From this, they conclude that costs exceed benefits by 7 cents ($0.07)
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Economic Considerations 59 troversial, even if they are based on the latest techniques (such as the willingness-to-pay approach)
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60 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS estimate some economic value of the labor of those not directly in the labor market (thus housewives, at least, can be included)
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Economic Considerations 61 sumers favor vehicles that they perceive as safer over less safe vehicles. The availability of automatic restraint systems in models was found to enhance the likelihood of purchasing a given model, but McCarthy tempered this finding because of the paucity of data.
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62 SAFETY BELTS, AIRBAGS, AND CHILD RESTRAINTS REFERENCES Blomquist, G
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APPENDIX A Reviewers of the Draft Report PHYLLIS AGRAN, Department of Pediatrics, University of California, 101 City Drive South, Orange, Calif. 92668 EDWARD BERNSTEIN, Emergency Medicine, University of New Mexico, 620CaminodeSalud, N.E., Albuquerque, N.Mex.
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APPENDIX B Calculation of Expected Benefits of. Mandatory Use Laws The equation developed by Evans (1987)
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66 If the same assumptions are used, it can be suggested that belt use laws would result in a 17.9 percent reduction in fatalities. REFERENCES Evans, L
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Study Committee Biographicth Information MARY BETH BERKOFF, Chairman, is an account executive with BursonMarsteller. A graduate of the University of Michigan, Berkoff has also held executive positions with Daniel J
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68 University. Bryer served PennDOT in various highway design and safety capacities for 14 years before assuming his current position, in which he supervises divisions that deal with accident information management, program services, and motor carrier safety.
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69 ELIZABETH M ORSAY is a physician with the Division of Emergency Medicine, Lutheran General Hospital, Park Ridge, Illinois, and also Assistant Professor of Clinical Emergency Medicine at the College of Medicine, University of Illinois.
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The Transportation Research Board is a unit of the Nation'al Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board's purpose is to stimulate research concerning the nature and performance of transportation systems, to disseminate the information produced by the research, and to encourage the application of appropriate research findings.
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C fi cD 00 - 00 tg o od 4 3 000 C 3 0 0 S S 0 3 a 0 0 1' 4 a a: S a 0 0 S C C 0 0 a, 0 C S 3 ol 0 0 z 0 LI ILl Oa 0 - z ISBN 0-309-04755-2
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