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Table 1. Characteristics of Intervention and Control Neighborhoods in 2000*
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Table 2. Characteristics of Children Eligible for a Booster Seat and of Drivers of Vehicles in Which These Children Were Riding*
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Table 3. Observed Booster Seat Use in Intervention and Control Neighborhoods*
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1.
Centers for Disease Control and Prevention.  Working to Prevent and Control Injury in the United States: Fact Book for the Year 2000. Atlanta, Ga: US Dept of Health and Human Services, Centers for Disease Control and Prevention; 2000.
2.
Winston FK, Durbin DR, Kallan MJ, Moll EK. The danger of premature graduation to seat belts for young children.  Pediatrics.2000;105:1179-1183.
3.
Centers for Disease Control and Prevention, National Center for Injury Prevention and Control.  National child passenger safety week: February 10-16, 2002. Available at: http://www.cdc.gov/ncipc/duip/spotlite/chldseat.htm. Accessed August 21, 2002.
4.
Ebel BE, Koepsell TD, Bennett EE, Rivara FP. Too small for a seat belt: an observational survey of booster seat use by child passengers.  Pediatrics.In press.
5.
Cody B, Mickalide A, Paul H, Colella J. Child Passengers at Risk in America: A National Study of Restraint Use. Washington, DC: National SAFE KIDS Campaign; 2002.
6.
US Census Bureau: American FactFinder.  Profile of Selected Social Characteristics: 2000. Available at: http://factfinder.census.gov/servlet/QTTable?ds_name=ACS_C2SS_EST_G00_&geo_id=01000US&qr_name=ACS_C2SS_EST_G00_QT02. Accessed September 24, 2001.
7.
National Association of Realtors.  The salary calculator. Available at: http://www.homefair.com/homefair/calc/salcalc.html. Accessed November 1, 2002.
8.
Green LW, Kreuter MW. Health Promotion Planning: An Educational and Ecological Approach. 3rd ed. Mountain View, Calif: Mayfield Publishing Co; 1999.
9.
Glanz K, Marcus Lewis F, Rimer B. Health Behavior and Health Education: Theory Research and Practice. 2nd ed. San Francisco, Calif: Jossey Bass Inc; 1997.
10.
Bandura A. Social Foundations of Thought and ActionEnglewood Cliffs, NJ: Prentice-Hall; 1986.
11.
Rivara FP, Bennett E, Crispin B.  et al.  Booster seats for child passengers: lessons for increasing their use.  Inj Prev.2001;7:210-213.
12.
Washington State Booster Seat Coalition.  Available at: http://www.boosterseat.orgAccessed May 10, 2002.
13.
American Academy of Pediatrics.  Car safety seats: a guide for families, 2002. Available at: http://www.aap.org/family/carseatguide.htm. Accessed May 10, 2002.
14.
National Highway Traffic Safety Administration.  A parent's guide to buying and using booster seats. Available at: http://www.nhtsa.gov/people/injury/childps/booster_seat/newboosterseats/finalcor2.pdf. Accessed January 9, 2003.
15.
Klinich KD, Pritz HB, Beebe MS.  et al.  Study of Older Child Restraint/Booster Seat Fit and NASS Injury Analysis. Springfield, Va: National Highway Traffic Safety Administration, US Dept of Transportation; 1994.
16.
Murray DM. Design and Analysis of Group-Randomized Trials. Vol 27. Oxford, England: Oxford University Press; 1998.
17.
Rabe-Hesketh S, Pickles A, Skrondal A. GLLAMM Manual Technical Report 2001/01. London, England: Dept of Biostatistics and Computing, Institute of Psychiatry, King's College, University of London; 2001.
18.
Greenland S. Estimating standardized parameters from generalized linear models.  Stat Med.1991;10:1069-1074.
19.
Bidez MW, Syson SR. Kinematics, Injury Mechanisms, and Design Considerations for Older Children in Adult Torso Belts. Detroit, Mich: SAE Technical Paper Series; 2001. Reprinted from Biomechanics Research and Development (SP-1577).
20.
National Center for Health Statistics, Centers for Disease Control and Prevention.  2000 CDC growth charts: United States. Available at: http://www.cdc.gov/growthcharts/. Accessed June 17, 2002.
21.
Korner J. Booster seat data from Volvo Presonvagnar AB, accident base. Paper presented at: Association for the Advancement of Automotive Medicine Conference on Booster Seats; April 23, 2001; Washington, DC.
22.
Ramsey A, Simpson E, Rivara FP. Booster seat use and reasons for nonuse.  Pediatrics.2000;106:E20.
23.
McLeroy K, Bibeau D, Steckler A, Glanz K. An ecological perspective on health promotion programs.  Health Educ Q.1988;15:351-377.
24.
Bergman AB, Rivara FP, Richards DD, Rogers LW. The Seattle children's bicycle helmet campaign.  AJDC.1990;144:727-731.
25.
Rivara FP, Thompson DC, Thompson RS.  et al.  The Seattle children's bicycle helmet campaign: changes in helmet use and head injury admissions.  Pediatrics.1994;93:567-569.
Original Contribution
February 19, 2003

Use of Child Booster Seats in Motor Vehicles Following a Community CampaignA Controlled Trial

Author Affiliations

Author Affiliations: Departments of Pediatrics (Drs Ebel and Rivara) and Epidemiology (Drs Koepsell and Rivara), and Harborview Injury Prevention and Research Center (Drs Ebel, Koepsell, and Rivara), University of Washington, Seattle; and Children's Hospital and Regional Medical Center, Seattle, Wash (Ms Bennett).

JAMA. 2003;289(7):879-884. doi:10.1001/jama.289.7.879
Context

Context Once children have outgrown car seats, booster seats protect from injury better than lap and shoulder belts alone. However, the majority of children aged 4 to 8 years use only an adult seat belt.

Objective To evaluate the effectiveness of a multifaceted community booster seat campaign in increasing observed booster seat use among child passengers in motor vehicles.

Design Prospective, nonrandomized, controlled community intervention trial.

Setting and Participants The campaign was initiated in 4 communities in the greater Seattle, Wash, area between January 2000 and March 2001. Eight communities in Portland, Ore, and Spokane, Wash, served as control sites. We observed 3609 booster-eligible children (those aged 4-8 years and weighing 18-36 kg [40-80 lb]).

Main Outcome Measure Observed booster seat use 15 months after the start of the campaign.

Results Before the campaign began, 13.3% of eligible children in the intervention communities and 17.3% in the control communities were using booster seats, adjusting for child age, driver seat belt use, and sex of driver. Fifteen months after the start of the campaign, adjusted booster seat use had increased to 26.1% in the intervention communities and 20.2% in the control communities (P = .008 for the difference in time trends between intervention and control communities).

Conclusion These data suggest that a multifaceted community education campaign can significantly increase the use of child booster seats.

Motor vehicle collisions remain the leading cause of death for children aged 4 to 8 years.1 Booster seats are more effective than seat belts at reducing the risk of injury for these older children.2 Nonetheless, only an estimated 6% to 19% of 4- to 8-year-old children currently ride in booster seats, while the majority use only an adult seat belt.35 To date, there are no published trials of community interventions to increase booster seat use. In 1999, we began a 2-year community campaign to increase booster seat use in King County, Washington. This report describes the effectiveness of the campaign in increasing observed booster seat use.

METHODS
Study Design

We conducted a prospective, nonrandomized, controlled trial to evaluate the community intervention. Booster seat use in each community was observed at baseline just before beginning the intervention, and then observations were repeated 15 months later. Four communities in the greater Seattle, Wash, area served as intervention sites, comprising about 240 000 people. Eight communities in Portland, Ore, and Spokane, Wash, served as control sites. These communities were approximately matched on household per capita income and population size (Table 1),6,7 and were chosen because they represented distinct neighborhoods with clear geographic boundaries.

Booster Seat Campaign

The campaign targeted both parents and children. It sought to increase parental awareness of the need for booster seats, reduce the motivational and financial barriers to purchasing a seat, and reinforce booster seat use through public health messages delivered from many different sources. Campaign messages were developed based on the Precede-Proceed model of behavioral change, identifying predisposing, enabling, and reinforcing factors affecting behavior.8 Parents perceived that seat belts provided adequate protection, increasing awareness with the campaign slogan, "Is Your Child Ready for Seat Belt? Think Again!" To address parental confusion and lack of knowledge, all secondary messages provided specific guidelines for booster seat use. Enabling factors included a focus on health care providers as disseminators of information and the use of discount coupons. A new booster seat law served as an important reinforcing factor.

Social marketing provided the structure for campaign development.9 Audience focus was narrowed to particularly target parents with younger children aged 3 to 5 years. The booster seat message was clear and specific. A variety of tactics were used, including media, publicity, education outreach, policy change, and provider education, all of which used a consistent message and approach. Messages emphasized the benefits of booster seat use and the consequences of not using one. Social learning theory constructs were considered in specific program elements and approach.10 Contents of materials were designed to build parent confidence in choosing and using a booster seat, and to provide the knowledge parents needed to make informed decisions.

Before the campaign launch, we conducted 3 focus groups with parents to investigate reasons for booster seat use and nonuse and test the efficacy of our public health messages.11 Participants were recruited from child care centers in Seattle area neighborhoods. They all had at least 1 child aged 3 to 5 years, had mixed incomes, and may or may not have been using a car seat or booster seat. Participants responded to a range of questions about their booster seat knowledge, attitudes, beliefs, and behaviors. A professional focus group facilitator conducted each session and summarized key themes and messages. Information from the focus groups guided message development and priorities.

We developed the King County Booster Seat Coalition to bring together parents, public health professionals, community outreach workers, childcare providers, law enforcement officers, physicians, emergency medical technicians, and educators. Coalition members helped set priorities for the campaign and spearheaded outreach efforts with child care providers, schools, and parents. They developed classes and health fair events for families and disseminated booster seats, materials, and discount coupons.

Based on the findings of our focus groups and in consultation with the coalition and a parent feedback committee, we designed a multifaceted public education campaign (Box). All educational materials provided information on why seat belts are not adequate and how a booster seat can help position a child in the car and make him/her more comfortable. Materials included images of different types of booster seats, because many parents indicated that they were confused by the varying styles. Brochures provided parenting suggestions to address parental perceptions of peer pressure by other children to not use a booster seat. We created public service announcements for television, radio, and print media, targeting community newspapers and parent magazines. An easy-to-read pamphlet was designed and translated into 7 different languages. Specific intervention materials and programs were designed for health professionals, child care facilities, schools, and community fairs. A booster seat telephone hotline was set up through the Washington Safety Restraint Coalition. Callers could request materials and coupons and could ask car-specific questions from car-safety experts. We established a Web site (http://www.boosterseat.org), on which parents could find information about booster seats, a fit test, request materials or a coupon, answer commonly asked questions, find locations for car-seat checks, and find links to the growing body of helpful Web sites with booster seat information. The Web site has received steadily increasing traffic with 81 000 hits per month by August 2002.12

With support from a booster seat manufacturer and a retail outlet, we negotiated a coupon that provided $10 off the price of a low-back booster seat, lowering the price of this seat to less than $20. These coupons were available through child care centers, physicians' offices, community organizations, a toll-free telephone hotline, or via our booster seat campaign Web site. The study was approved by the institutional review boards at the University of Washington Human Subjects Division.

Box. Booster Seat Campaign Elements

Community coalition of agencies and organizations to promote the use of booster seats

Citizen advisory group of parents and caregivers to provide feedback on campaign messages and materials and to develop strategies to ensure community involvement

Broad-based community education program to increase knowledge and awareness of the importance of booster seat use, which included:
Newspaper articles
Organization and group newsletter articles
Booster seat Web site
Tip sheet, brochures, and flyers in multiple languages
Telephone information line where parents can call for materials and with questions about booster seats and car seats
Resource kits for preschools and health care providers
Radio public service announcements
Television public service announcements
Local news reports
Educational programs to address barriers to booster seat use, including defining types of booster seats, identifying where devices are available, and providing alternatives for automobiles with lap-only belts

Discount booster seat coupons

Car seat training programs and in-services for health care providers, child care providers and educators, law enforcement, emergency medical service personnel, and child passenger safety advocates

Data Collection

We measured baseline booster seat use in each of the 12 communities beginning in January 2000. Follow-up observations were conducted 15 months later beginning in March 2001. We conducted observations at 83 child care centers and after-school programs, as has been previously described.4 Because the booster seat promotion campaign was neighborhood-based, these sites were chosen to measure booster seat use in the local 4- to 8-year-old population, rather than the wider population of children one might expect to find at a toy store or larger shopping center. Fast-food sites were pilot-tested but were not used as observation sites because very few booster eligible-children per hour were observed, making observations too inefficient, and because several communities had only 1 or 2 fast-food restaurants within their borders. Random intersection sites were not used because the study required that vehicles be stopped and approached, so that drivers could be directly questioned about child age and weight.

We obtained consent from the center directors and obtained oral consent from all participating drivers. Centers were asked to withhold information to the parents about the scheduling of the survey, so as not to alter routine behavior. A pilot study was conducted to determine the feasibility of the observational study and brief survey. Observers were recruited from local colleges and communities and underwent a standard training program to explain the aims of the study and the methodology. Practice observations were conducted under supervision before data collection. Teams of 2 or more observers visited each site. Cars were approached in the parking lot at pickup times only after the driver had an opportunity to secure any children in the vehicle, and to fasten his/her own seat belt. Cars leaving with only a nonambulatory child were excluded from the survey. Drivers reported child's age, weight and height, and distance from home. Trained observers looked into the car to assess actual restraint use by the driver and all occupants.

Data Analysis

Advocates recommend booster seats for children who have outgrown child harness seats (usually at 18 kg [40 lb] or around age 4 years) until they fit properly in the vehicle seat belt.13,14 Children do not fit into the adult seat belt well until they are 143 cm tall, generally at around 36 kg (80 lb), and at least 8 years.15 The American Academy of Pediatrics states that a child should stay in a booster seat until the belt fits, usually when the child reaches about 143 cm in height and is between 8 to 12 years of age.13 Because the majority of drivers in our survey were unable to report a child height, raising concerns that those who did may have reported inaccurate heights, we chose to use only age and weight criteria to define recommended booster seat use. We defined a child who should use a booster seat as any child between 18 and 36 kg (40-80 lb) and aged between 4 to 8 years, or a child aged between 4 to 8 years when weight data were not available. Three-year-old children weighing 18 kg (40 lb) were also characterized as being booster seat eligible, because the majority of child harness seats have a maximum weight limit of 18 kg (40 lb). Ten children were 2 years of age and were reported to weigh 18 kg (40 lb) or more. These children were considered to be too young for booster seat use and were classified as child harness seat users. Children who were more than 36 kg (80 lb) or older than 8 years were considered to be big enough for the adult lap and shoulder belt. There were no 3-year-old children who weighed more than 36 kg (80 lb), and no 8-year-old children weighing less than 18 kg (40 lb).

The overall effectiveness of the intervention was estimated using a generalized linear mixed model, adjusted for child level variables (age, sex), car level variables (driver sex, driver seat belt use), and incorporated the effects of clustering at the levels of car, site, and community.16,17 The adjusted prevalence of booster seat use in each community was obtained using model-based direct adjustment,18 using the combined population of all studied children as the standard population. Data were analyzed with STATA version 7.0 (Stata Corp, College Station, Tex) and P≤.05 was considered statistically significant.

RESULTS

We observed 5656 children traveling in cars during baseline and follow-up observations, 3609 of whom were eligible for booster seat use based on age and weight criteria. Eighty-five percent of drivers approached agreed to our survey; there was no significant difference in response rate by community. Among children eligible for a booster seat, mean age was 5 years and mean weight was approximately 23 kg (50 lb). Half of all drivers were surveyed within 11 minutes by car from home. Eighty-three percent of drivers were wearing a seat belt themselves. Nearly 70% of drivers were female (Table 2).

The overall effectiveness of the intervention was estimated using a generalized linear mixed model, allowing for adjustment by child level variables (child age) and car level variables (driver sex and seat belt use), while incorporating the effects of nested clustering by car, site, and community.16,17Table 3 shows the adjusted prevalence of booster seat use by study group and observation time. Adjustment was performed using model-based direct adjustment,18 using the combined population of all studied children as the standard population. Therefore, each adjusted prevalence may be interpreted as the prevalence of booster seat use that would have been observed in a certain study group at a certain time if such children had had the same distribution of covariates (age, driver sex, driver seat belt use) as did the study population as a whole. The adjusted prevalence of booster seat use in intervention communities was 13.3% at baseline and rose to 26.1% at follow-up. In the control communities, the adjusted prevalence of baseline booster seat use was 17.3% and increased to 20.2% at follow-up (P = .008 for the difference in time trends between intervention and control communities), albeit with considerable variation among neighborhoods. Child sex and distance from home were not significant predictors or confounders of booster seat use in the final multivariate model.

Booster seat use decreased with increasing child age. At follow-up, booster seat use was greatest for 4- to 6-year-old children (26%) and was uncommon for children aged 7 to 8 years (9%). For each additional year of age, the odds ratio (OR) of using a booster seat was 0.71 (95% confidence interval [CI], 0.65-0.76), indicating that an older child was significantly less likely to be properly restrained in a booster seat. Driver use of seat belts was also strongly associated with correct booster seat use, with an OR of 5.51 (95% CI, 2.86-10.65). Female drivers were more likely to be driving child passengers correctly restrained in booster seats than were male drivers (OR, 1.56; 95% CI, 1.04-2.33).

COMMENT

To our knowledge, this is the first controlled evaluation of a community intervention designed to increase booster seat use. We found that our campaign significantly increased booster seat use among booster-eligible children in intervention communities relative to control communities.

Most children who are aged between 4 to 8 years, weigh between 18 and 36 kg (40-80 lb), or with height less than 143 cm do not fit well into an adult seat belt.14,15,19 Recent anthropometric data suggest that a child who is at least 143 cm tall and weighs at least 36 kg (80 lb) has a median age of 11 years20; therefore, the recommendation that booster seats be used by children who are younger than 8 years recognizes that most 8-year-old children will meet the height and weight criterion for booster seat use. Data from mechanical sled tests,15,19 computer crash simulations, and the limited epidemiological data available2,21 all suggest that booster seats are protective for children who do not yet fit into seat belts. Therefore, safety experts recommend that children who have outgrown child harness seats and do not yet fit adult seat belts should use a booster seat, generally children younger than 8 years and 36 kg (80 lb).13,14 However, this study shows that most booster-eligible children are not using booster seats and may be inadequately protected in a crash.

Focus group studies we conducted before beginning the booster seat campaign found that many parents did not know about booster seats or had an inaccurate understanding of when it is safe to move a child to a lap shoulder belt.11,22 Parents reported that they had not received consistent information about when a child should be in a booster seat. Other barriers to booster seat use included child resistance, peer pressure, and difficulty finding affordable booster seats.

To encourage booster seat use, we designed a coordinated, community education campaign using multiple avenues for getting parents information about booster seats. Health promotion theory suggests that multicomponent interventions are likely to be more effective at changing behavior.8,23 A similar community-based campaign was successful at promoting the use of bicycle helmets and reducing bicycle-related head injury.11,24,25 The development of a coalition of community members, educators, public health officials, and health care and child care providers continues to provide input and guidance to the intervention. There has been continued demand for informational brochures, as well as steadily increasing local and national traffic on the booster seat Web site and telephone hotline.

The increasing national emphasis on booster seat use by the National Highway Traffic Safety Administration, Safe Kids Coalitions, and others contributed additional positive messages to parents, although presumably the control communities in our study were exposed to these same messages. In addition, the legislatures of Washington and Oregon both passed booster legislation during the time course of the study, although in both instances the legislation did not go into effect until after the intervention period, and the proposed legislation would have affected both control and intervention sites.

Our study design allowed control for the effects of other state and national booster seat initiatives to see the effect of a more focused community-based campaign. Demonstrated effectiveness at increasing booster seat use may also provide impetus for other states to invest in community campaigns and to consider legislative changes in support of booster seat use.

Our results also demonstrated variability in neighborhood booster seat usage patterns. We cannot say exactly why this variation occurred, but there are multiple exogenous factors that contribute to the prevalence of prevention behaviors in the community. We were interested in knowing the effects of the special campaign over and above changes that might have occurred to other information in the community, region, or nation. We are not aware of any particular reason for the variations in booster seat prevalence. In 1 comparison community, the prevalence of booster seat use increased quite dramatically from 21% to 54%. This was an affluent community, with high prevalence of booster seat use during baseline observations. Data were analyzed, including this site as a control site, and therefore the increase in booster seat use in this community was fully accounted for in the data analysis.

This study had a number of limitations. It was conducted in 3 northwest cities and therefore may not be generalizable to other parts of the country. It was not a randomized study, so there is always the possibility of unmeasured confounders. We attempted to reduce the effects of confounding by comparing booster use in each community to baseline booster use in the same community. The design of this study did not permit us disaggregate intervention components to determine which were most effective. Finally, our study relied on a brief and noninvasive survey. We were therefore not able to physically measure children but relied instead on parental report of age, weight, and height.

In conclusion, this multifaceted community campaign was able to significantly increase booster seat use among booster-eligible children. It shared elements with other successful community-based injury strategies in that it had a strong theoretical basis, involved coalition-building, relied on a focused public health message, used focus groups to guide campaign messages and development, and included an evaluation of campaign effectiveness. This program might serve as a useful model for other communities working on injury-prevention strategies.

References
1.
Centers for Disease Control and Prevention.  Working to Prevent and Control Injury in the United States: Fact Book for the Year 2000. Atlanta, Ga: US Dept of Health and Human Services, Centers for Disease Control and Prevention; 2000.
2.
Winston FK, Durbin DR, Kallan MJ, Moll EK. The danger of premature graduation to seat belts for young children.  Pediatrics.2000;105:1179-1183.
3.
Centers for Disease Control and Prevention, National Center for Injury Prevention and Control.  National child passenger safety week: February 10-16, 2002. Available at: http://www.cdc.gov/ncipc/duip/spotlite/chldseat.htm. Accessed August 21, 2002.
4.
Ebel BE, Koepsell TD, Bennett EE, Rivara FP. Too small for a seat belt: an observational survey of booster seat use by child passengers.  Pediatrics.In press.
5.
Cody B, Mickalide A, Paul H, Colella J. Child Passengers at Risk in America: A National Study of Restraint Use. Washington, DC: National SAFE KIDS Campaign; 2002.
6.
US Census Bureau: American FactFinder.  Profile of Selected Social Characteristics: 2000. Available at: http://factfinder.census.gov/servlet/QTTable?ds_name=ACS_C2SS_EST_G00_&geo_id=01000US&qr_name=ACS_C2SS_EST_G00_QT02. Accessed September 24, 2001.
7.
National Association of Realtors.  The salary calculator. Available at: http://www.homefair.com/homefair/calc/salcalc.html. Accessed November 1, 2002.
8.
Green LW, Kreuter MW. Health Promotion Planning: An Educational and Ecological Approach. 3rd ed. Mountain View, Calif: Mayfield Publishing Co; 1999.
9.
Glanz K, Marcus Lewis F, Rimer B. Health Behavior and Health Education: Theory Research and Practice. 2nd ed. San Francisco, Calif: Jossey Bass Inc; 1997.
10.
Bandura A. Social Foundations of Thought and ActionEnglewood Cliffs, NJ: Prentice-Hall; 1986.
11.
Rivara FP, Bennett E, Crispin B.  et al.  Booster seats for child passengers: lessons for increasing their use.  Inj Prev.2001;7:210-213.
12.
Washington State Booster Seat Coalition.  Available at: http://www.boosterseat.orgAccessed May 10, 2002.
13.
American Academy of Pediatrics.  Car safety seats: a guide for families, 2002. Available at: http://www.aap.org/family/carseatguide.htm. Accessed May 10, 2002.
14.
National Highway Traffic Safety Administration.  A parent's guide to buying and using booster seats. Available at: http://www.nhtsa.gov/people/injury/childps/booster_seat/newboosterseats/finalcor2.pdf. Accessed January 9, 2003.
15.
Klinich KD, Pritz HB, Beebe MS.  et al.  Study of Older Child Restraint/Booster Seat Fit and NASS Injury Analysis. Springfield, Va: National Highway Traffic Safety Administration, US Dept of Transportation; 1994.
16.
Murray DM. Design and Analysis of Group-Randomized Trials. Vol 27. Oxford, England: Oxford University Press; 1998.
17.
Rabe-Hesketh S, Pickles A, Skrondal A. GLLAMM Manual Technical Report 2001/01. London, England: Dept of Biostatistics and Computing, Institute of Psychiatry, King's College, University of London; 2001.
18.
Greenland S. Estimating standardized parameters from generalized linear models.  Stat Med.1991;10:1069-1074.
19.
Bidez MW, Syson SR. Kinematics, Injury Mechanisms, and Design Considerations for Older Children in Adult Torso Belts. Detroit, Mich: SAE Technical Paper Series; 2001. Reprinted from Biomechanics Research and Development (SP-1577).
20.
National Center for Health Statistics, Centers for Disease Control and Prevention.  2000 CDC growth charts: United States. Available at: http://www.cdc.gov/growthcharts/. Accessed June 17, 2002.
21.
Korner J. Booster seat data from Volvo Presonvagnar AB, accident base. Paper presented at: Association for the Advancement of Automotive Medicine Conference on Booster Seats; April 23, 2001; Washington, DC.
22.
Ramsey A, Simpson E, Rivara FP. Booster seat use and reasons for nonuse.  Pediatrics.2000;106:E20.
23.
McLeroy K, Bibeau D, Steckler A, Glanz K. An ecological perspective on health promotion programs.  Health Educ Q.1988;15:351-377.
24.
Bergman AB, Rivara FP, Richards DD, Rogers LW. The Seattle children's bicycle helmet campaign.  AJDC.1990;144:727-731.
25.
Rivara FP, Thompson DC, Thompson RS.  et al.  The Seattle children's bicycle helmet campaign: changes in helmet use and head injury admissions.  Pediatrics.1994;93:567-569.
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