Chapter 22. Young Children and “Tweens”
Kelli England Will
Eastern Virginia Medical School, Norfolk, VA, USA
Children are especially susceptible to road traffic injury, and morbidity and mortality rates throughout the world reflect this vulnerability. Often, transport projects are not designed with the unique safety needs of children in mind. The unfortunate interplay between the roadway environment and children's developmental limitations has resulted in a global pandemic of road traffic injuries among children. This chapter reviews the burden of road traffic injury on children, highlighting global economic disparities and regional differences in priority issues and standard practices for protecting children. Following a brief review of key strategies for preventing road traffic injuries among children as vulnerable road users (e.g., pedestrians and cyclists), detailed recommendations are provided for protecting child occupants in motor vehicles. Occupant crash dynamics, restraint use recommendations by developmental stage, rear seating benefits, and additional challenges and barriers are discussed. Finally, recommended and empirically supported interventions for child passenger safety are summarized.
If a disease were killing our children in the proportions that injuries are, people would be outraged and demand that this killer be stopped.
—C. Everett Koop, U.S. Surgeon General, 1982–1989

1. Introduction

Road traffic injury is the leading cause of global injury death and the ninth leading cause of disease burden (World Health Organization, 2009). There are more than 1.2 million deaths and as many as 50 million traffic-related injuries in the world per year (World Health Organization, 2009). The global cost of traffic injuries is estimated to be $518 billion, costing governments between 1 and 3% of their gross national product (World Health Organization, 2009). If the current trends continue, road traffic injuries are predicted to be the fifth leading cause of disease burden for all ages by the year 2030 (World Health Organization, 2009).
Children are especially susceptible to road traffic injury, and morbidity and mortality rates throughout the world reflect this vulnerability. Children interact with roadways in a number of ways. In most low- and middle-income countries, the majority of road users are not vehicle occupants but, rather, vulnerable road users without a protective shell around them. These include pedestrians, cyclists, motorcycle passengers, and passengers loading and unloading from public transport (Peden et al., 2008 and World Health Organization, 2009). Often, transport projects are not designed with the unique safety needs of children and other vulnerable road users in mind (Toroyan and Peden, 2007 and World Health Organization, 2009). Children may be required to walk alongside or weave in and out of traffic during their daily routines as they walk to school, complete their chores, and seek open areas to play.
This, coupled with children's limitations in development, is a recipe for disaster. In addition to the risk stemming from the manner in which children interact with the roadway environment, children possess a number of unique developmental characteristics that play into their susceptibility to roadway injuries (Toroyan & Peden, 2007). Children's bodies are small and still developing and thus are less able to withstand crash forces. Small body mass also means they are not easily seen by motorists, nor can they view surrounding traffic. Furthermore, children's disproportionally large head size leads to a greater number of head injuries given their higher center of gravity. Judgments of speed and distance are difficult for children due to underdeveloped visual depth perception, hearing, and kinesthetic senses. Children are also prone to limitations in attention, engage in more risk taking, are more susceptible to social influence, and are generally inexperienced in accurately perceiving hazards in their environment (Toroyan & Peden, 2007).
The unfortunate result of the interplay between the roadway environment and these developmental limitations is the global pandemic of road traffic injuries the world's children are currently experiencing. One-fifth of all road traffic deaths are among children (Peden et al., 2008). Every year, approximately 262,000 of the world's children are killed and an estimated 10 million are injured in roadway crashes (Peden et al., 2008). Globally, traffic injuries are among the top three causes of death for children older than age 5 years. For children aged 1–4 years, traffic injuries are among the top 10 causes of death (Toroyan and Peden, 2007 and World Health Organization, 2009). By 2015, roadway injuries are predicted to be the number one cause of death and disability for all children older than age 4 years (Mathers & Loncar, 2005).
Traffic-related injuries to children are most commonly head and limb injuries, often resulting in death or long-term disability (Peden et al., 2004 and Toroyan and Peden, 2007). Traumatic brain injuries are the most frequent cause of traffic-related deaths and injuries in countries of all income levels (Peden et al., 2004, Peden et al., 2008 and Toroyan and Peden, 2007). Chest and abdominal injuries are less common by comparison but still frequent and very serious given the complexity of managing damage to internal organs (Peden et al., 2008). Following crashes, children and their families experience a myriad of issues, including coping with loss of a loved one; disabilities and impairments; financial hardships; costly and often substandard medical care; and high levels of psychosocial distress, including anxiety and post-traumatic stress disorder (Peden et al., 2008).

2. Global Economic Disparities in Road Traffic Injuries

Unfortunately, the road traffic injury burden falls disproportionately on children from poorer economic settings. Despite the fact that the majority of the world's vehicles are in high-income countries, more than 90% of motor vehicle-related deaths occur in low- and middle-income countries (Peden et al., 2004, Peden et al., 2008 and World Health Organization, 2009). For instance, two-thirds of the world's annual crash deaths occur in the low- and middle-income countries of the Southeast Asia, African, and Western Pacific regions (Peden et al., 2008). Furthermore, the worst road death rate is in Africa, which has very few vehicles relative to the rest of the world. Consider that Africa has a road traffic injury mortality rate of 19.9 per 100,000 children, whereas the corresponding rate in the high-income countries of the European region is 5.2 per 100,000 children (Peden et al., 2008).
Road traffic injuries remain a leading cause of death and disproportionately affect the poor even in wealthy countries. However, in wealthy countries, fatality rates are decreasing despite increases in motorization (Safe Kids Worldwide, 2004). In most high-income countries, slow increases in motorization have allowed safety practices to develop in concert with increased traffic volume. In Finland, for instance, 30 years of road safety campaigns have led to a 50% decrease in fatalities, despite tripling of the country's traffic volume (United Nations, 2003).
Conversely, in low- and middle-income countries, fatality rates are increasing. For instance, child traffic deaths increased by one-third in China and sub-Saharan Africa during the 1990s (Safe Kids Worldwide, 2004). Unlike the development of traffic safety practices in high-income countries, developing nations are becoming motorized at such a rapid pace that appropriate safety measures and regulations are lagging (World Health Organization, 2009). Many low- and middle-income countries contend with poor roads, lax enforcement of driving rules, multi-use roadways, and too few controlled intersections and safe pedestrian crossings (World Health Organization, 2009).
Economic disparities in road traffic injuries are expected to worsen. By 2020, road traffic injuries are predicted to increase by 83% in low- and middle-income countries and decrease by 27% in high-income countries. The resulting global increase in traffic-related injuries is expected to be 67% (Peden et al., 2004). Road traffic deaths in India and China alone are expected to increase approximately 147 and 97%, respectively, by 2020 (Kopits & Cropper, 2005). Despite the growing magnitude of the problem in developing countries, road traffic injuries are often neglected in these countries' research and policy initiatives (World Health Organization, 2009).

3. Regional Differences in Priority Issues and Standard Practices for Protecting Children

The purpose of this discussion is to underscore the variability and dissention throughout the world in road safety practices and regulations regarding children. Developing countries struggle with a number of unique road traffic risks. For instance, a primary problem in many countries is that pedestrians, cyclists, and motor vehicles share the road. Like pedestrians, small vehicles such as motorbikes are also considered vulnerable road users because many developing nations have multi-use roadways and lack load-limit or oversized vehicle standards. Comparatively speaking, tiny two-wheeled motorbikes ride alongside towering trucks overloaded with cargo. It is common for children to ride as passengers on motorbikes, and often helmets are not required or are not the norm. Roadway crowding can be a problem in some areas, and the density is further complicated by unclear or absent lane markings. Roadways may be unpaved or in otherwise poor condition in many areas. Other localities struggle with vehicle scarcity. Vehicle scarcity presents a problem when getting to a destination overrides the need for safe travel. It is not uncommon in Mali, Africa, for instance, to witness vehicles overloaded with occupants to the point that passengers catch rides by hanging onto the back of vehicles at speeds as high as 45 mph. Crucial risk factors for children in developing countries include poor implementation of road safety measures and underutilization of safety devices such as seat belts, child restraints, and helmets.
In low-income countries, most fatalities are among vulnerable road users (e.g., pedestrians and cyclists), whereas in high-income countries most are among vehicle occupants (World Health Organization, 2009). Consider that 70% of traffic deaths in the low- and middle-income countries of the Western Pacific are among vulnerable road users, whereas almost the opposite is true in the high-income countries of the Americas, with 65% of traffic deaths occurring among vehicle occupants (World Health Organization, 2009). Despite decreases in road traffic fatality rates in high-income countries, road traffic injury remains a leading cause of death for children in developed nations. Thus, a primary concern in the United States and Sweden is better protection of children riding in vehicles. By contrast, priorities in localities such as Bangladesh and China include creation of safe pedestrian facilities and improving helmet use rates given the high death rates among vulnerable road users (World Health Organization, 2009).
Clearly, road injury risks need to be viewed in their local context because each nation has its own unique needs for intervention. Also, traffic-related risks in developing countries may be occurring alongside epidemics of potentially deadly diseases such as tuberculosis, malaria, and HIV/AIDS. Residents may be struggling with the uncertainty that comes with war, poverty, or food and shelter insecurity. Because of unique needs, risks are likely prioritized differently from nation to nation. Familiarity with a hazard also reduces perception of risk (Sandman, 1991 and Slovic, 1991); therefore, what seems highly risky to a high-income country may be viewed with relative complacency in a developing country (and vice versa).
In addition to having varying risk priorities, countries are at differing levels of need regarding child safety interventions. In many high-income countries, restraint usage is more than 90% (Peden et al., 2008). Therefore, these countries' main concern regarding restraints is misuse because research indicates that at least three out of four safety restraints are unintentionally misused, potentially reducing their effectiveness by half (Carlsson et al., 1991, Decina and Lococo, 2005, Dukehart et al., 2007 and Durbin et al., 2005). In contrast, the more immediate goals of intervention in many low-income countries would be increased use of age-appropriate child restraints, regardless of proper installation. Once use is increased, intervention agents can begin to focus on installation issues. Although related, the methods for increasing use versus correct use are quite different. Countries also differ regarding their most needed modes of intervention. Educational efforts may be warranted in some localities, whereas others may focus on engineering improvements. Some countries need to pass legislation, whereas others are only lacking in enforcement of existing legislation.

4. Key Strategies for Preventing Road Traffic Injuries Among Children

Keeping the differing priorities and needs throughout the world in mind, global leaders have collectively proposed a number of recommended measures that countries can work toward for improved roadway safety. The reader is referred to the comprehensive review of recommendations and evidence for their effectiveness contained in the World Report on Road Traffic Injury Prevention (Peden et al., 2004). Most road traffic injuries can be prevented with proper education, protective safety equipment, and safe systems approaches to roadway development (Peden et al., 2008 and World Health Organization, 2009). Unlike other public health problems (e.g., obesity and mental illness), many proven methods for reducing road traffic injury to children are well understood and agreed upon in the field (Peden et al., 2004). For instance, substantial proportions of injured children could be protected with safe pedestrian passageways, protective helmets, and optimal restraints and seating during travel. However, as any safety advocate knows, injury prevention mechanisms are only useful when they are prioritized by governments and utilized by the public.
Although all improvements in road safety measures will undoubtedly benefit children, interventions included in the World Report on Road Traffic Injury Prevention (Peden et al., 2004) that are specifically targeted to children and young road users include implementing engineering measures, improving vehicle design standards, increased use of safety equipment, enacting legislation and standards, developing education and skills, and improving emergency and trauma care (Peden et al., 2008). Such measures are detailed with regard to their impact on youth safety in the World Report on Child Injury Prevention (Peden et al., 2008). Thus, Peden and colleagues' (2008) conclusions are only summarized here.
The first recommended strategy, engineering measures, entails modifying the built environment to enhance child safety. Recommended engineering measures include techniques to reduce speed (e.g., speed humps and roundabouts), create safe play areas, provide safe routes to school, and physically separate two-wheelers from other traffic. Recommendations for improving vehicle design standards include requirements for energy-absorbing crumple zones and side-impact bars, redesign of car fronts for improved pedestrian-collision outcomes, improved fittings for child restraints, rear-visibility aids, and alcohol-interlock systems. The use of safety equipment should be enhanced with mandatory use laws, heightened enforcement, public awareness campaigns, and improved accessibility and affordability. Key safety equipment needs for children include developmentally appropriate child restraint systems; seat belts; bicycle helmets; motorcycle helmets; and improved conspicuity with retroreflective strips, bright colors, and daytime running lights. Stricter standards and legislation should be enacted and enforced regarding minimum age for motorized vehicle licensing, drink-driving prohibitions, mandatory seat belt and child restraint use, and mandatory helmet use. Efforts to further develop effective educational approaches are recommended, especially those that incorporate modern ecological models and are consistent with the state of the science in educational and behavior change theories. Finally, improving emergency, trauma, and rehabilitative care is important because maximum recovery from road traffic injuries is dependent on the availability, accessibility, and quality of such services (Peden et al., 2008).

5. Recommendations for Protecting Child Occupants in Motor Vehicles

5.1. Occupant Crash Dynamics and Safety Restraints

Sir Isaac Newton's first law of motion states that an object in motion keeps moving in the direction and speed it was traveling in unless it is stopped by something. In the case of a vehicle, the stopping mechanism could be the brakes, another vehicle, or a tree, pole, or other stationary object. In the case of the occupants in that vehicle, the stopping mechanism could be the windshield, seat belt, or anything else inside or outside the vehicle in the path of motion (National Highway Traffic Safety Administration (NHTSA), 2007). If the vehicle is traveling at 35 mph, occupants will continue traveling at 35 mph once the vehicle crashes, unless they are restrained and stop with the vehicle. There are three collisions during a vehicle crash: (1) the vehicle collision, as the vehicle begins to stop when it collides with another vehicle or object; (2) the human collision, as the occupants in the vehicle continue to move forward at the same speed until they collide with something inside or outside the vehicle; and (3) the internal collision, as the occupant's internal organs continue to move forward at the same speed until they collide with other organs and bones (NHTSA, 2007). Crash forces are quite powerful given the abrupt changes in momentum and velocity that occur in mere fractions of a second. To illustrate, one can consider the pounds of force needed to keep an occupant in position during a collision. This can be estimated fairly simply (albeit roughly) by multiplying a person's weight times the speed of the vehicle (NHTSA, 2007). For example, if a 90-pound child is properly restrained with a seat belt in a vehicle that crashes when going 30 mph, the restraining force provided by the seat belt in the crash is 2700 pounds. This roughly equals the weight of a small car. Thus, without a seat belt, the child will propel forward with the force of the weight of a small car.
Using a safety restraint dramatically reduces injury in a collision. Failing to wear a safety restraint increases one's odds of injury or death in a crash by 45–74%, depending on the type of restraint and seating position (Arbogast et al., 2009 and Durbin et al., 2005; NHTSA, 2010; Rice & Anderson, 2009). Properly fitted safety restraints prevent injury by (1) keeping occupants in the vehicle, (2) contacting the strongest parts of the body, (3) spreading forces over a wide area of the body, (4) helping the body slow down, and (5) protecting the brain and spinal cord (NHTSA, 2007). Chief among these is the prevention of ejection from the vehicle because an occupant is four times more likely to be killed if thrown from the vehicle during a crash (NHTSA, 2007).
Proper fit of a safety restraint is essential for maximum protection. Because safety belts are designed to fit the bodies of adults, safety belts alone are not sufficient for preventing injuries to small children (Arbogast et al., 2009 and Durbin et al., 2005; NHTSA, 2007). Indeed, the primary reasons for injuries to children who are restrained at the time of motor vehicle crashes relate to premature graduation from child safety seats to booster seats, premature graduation from booster seats to adult safety belts, prematurely turning a child forward, misuse of safety restraints, and children seated in the front seat of the vehicle (Arbogast et al., 2009, Berg et al., 2000, Braver et al., 1998, Durbin et al., 2005, Henary et al., 2007, Lennon et al., 2008, Rice and Anderson, 2009 and Winston and Durbin, 1999).
Young vehicle passengers are the most vulnerable in collisions because their bodies have not fully developed. In addition to their short stature and small body mass, children have pelvises that have not developed the iliac crest, a part of the hip bone that aids in keeping an adult safety belt correctly positioned low on the hips (NHTSA, 2007). The shoulder strap often falls across a child's face or neck, and the lap belt is incorrectly positioned over soft parts of the abdomen. To improve both comfort and safety, infants or toddlers should always ride in a child safety seat and small children in a belt-positioning booster (NHTSA, 2007). (Note that safety seats and booster seats are referred to in this chapter collectively as child restraints.) A child restraint is designed to either bear the majority of the crash forces (for a rear-facing child) or distribute the crash forces over the strongest parts of a child's body (NHTSA, 2007).
When correctly installed and used, child safety seats reduce the risk of fatal injury by as much as 74% for infants and 59% for toddlers (Rice & Anderson, 2009). Lap/shoulder safety belts reduce the risk of fatal injury to front seat occupants older than age 5 years by 45–60% and moderate-to-critical injury by 50–65% (NHTSA, 2010). However, children aged 4–8-years are 45% less likely to sustain injury when positioned in a belt-positioning booster seat versus a vehicle seat belt alone (Arbogast et al., 2009). Compared to appropriately restrained children (aged 0–15 years), unrestrained children are greater than three times more likely to sustain injury in a crash, and children traveling in inappropriate restraints for their size are at two times the risk of injury (Durbin et al., 2005). Furthermore, mistakes in restraint installation and use can hamper the restraint's ability to maximally protect from injury in a crash; many studies have shown that at least three out of four safety restraints are unintentionally misused (Decina and Lococo, 2005, Decina and Lococo, 2007, Dukehart et al., 2007 and O'Neil et al., 2009).

5.2. Restraint Use Recommendations by Developmental Stage

In many countries, best practice recommendations for occupant protection are organized by stages of development. Best practice recommendations represent the current knowledge of safety experts regarding the best methods for protecting children of various sizes in crashes. Because legislation usually lags behind knowledge given the slow process of policy change, best practice recommendations are used to guide advocates and caregivers in the interim.
Specific recommendations and timing of transitions vary by different regions of the world. In fact, child occupant recommendations and standards can be described as existing on a continuum, where some nations' recommendations maximally protect children, others do not protect children at all, and the majority of countries fall somewhere in between. For example, in Sweden, best practice recommendations place children in rear-facing seats until 4 years of age, after which they transfer directly to booster seats (Watson & Monteiro, 2009). Compare this with Afghanistan, where children are not required to be buckled at all (World Health Organization, 2009). Examples of countries that fall somewhere in between these two extremes include Argentina and the United States. Children in Argentina are not required to use child restraints but are required to use safety belts (World Health Organization, 2009). In the United States, all 50 states have a child restraint law, but requirements vary substantially by state and seldom reflect best practice. That is, many states' regulations fail to adequately protect booster-age children (Partners for Child Passenger Safety, 2007 and Ross et al., 2004). Child restraint crash performance standards also show great variation: Canada, Australia, and many European nations have stricter minimum performance standards for crash tests than does the United States (Llewellyn, 2000). Perhaps as a result, the United States does not require side-impact padding in child restraints as do many European nations. Although the United States is far advanced compared to many lower income countries, its crash-worthiness regulations and standard crash test procedures are lagging in comparison to some other high-income countries. Not surprisingly, regional variations in morbidity and mortality are inversely related to advances in safety practices and recommendations.
In the United States (and some other countries), parent education follows the “4 Steps for Kids” concept, emphasizing that there are four stages for proper restraint of a child in a vehicle. Each stage dictates a recommended restraint configuration and guidelines for minimum/maximum ages, weights, and heights. Because safety restraint weight and height ranges vary greatly, parents must read labels and instructions to determine if the seat is correct for a child's age, weight, and height.

5.2.1. Stage 1: Rear-Facing Seats

A baby's head is relatively large and heavy (comprising 25% of total body weight), and the neck and back are weak (NHTSA, 2007; Watson & Monteiro, 2009). With poor head and neck control, a young infant's head can fall forward and occlude the airway if seated upright. Furthermore, very young children's immature skeletal and organ development make them especially susceptible to injury and death from crash forces (NHTSA, 2007; Watson & Monteiro, 2009). In particular, frontal crash forces on a forward-facing child can lead to excessive stretching and even transection of the spinal cord due to the underdeveloped anatomy of the cervical spine (Watson & Monteiro, 2009). The odds of severe injury for forward-facing infants (<1 year) are 1.79 times higher than for rear-facing infants. Moreover, children 12–23 months old are 5.32 times more likely to sustain severe injuries when traveling in forward-facing versus rear-facing seats (Henary et al., 2007).
For these reasons, safety experts advise that infants and very young children ride semi-reclined at a 45-degree angle in a rear-facing seat that will cocoon around a baby's body and bear the majority of crash forces (Bull and Durbin, 2008 and Watson and Monteiro, 2009). Because most crashes are frontal collisions, simply facing a seat rearward dramatically changes the dynamics of the child's movement in the crash and places the majority of harmful forces on the seat versus the child (Henary et al., 2007; NHTSA, 2007). A child's head, neck, and spine are kept aligned, and the crash forces that are not absorbed by the safety seat are distributed over all these body areas (Watson & Monteiro, 2009).
Children should remain rear facing as long as possible to the maximum weight limit for the seat, provided the head is below the top of the seat; in the United States, it is currently recommended that children face rearward until 2 years of age and at least 20 pounds. However, safety advocates in many countries are increasingly advising rear facing until age 4 years due to the profound protective benefits for children (Henary et al., 2007 and Watson and Monteiro, 2009).
Infants and young toddlers should generally ride in an infant seat (often with a detachable base) or convertible seat that faces rearward at first, then converts to forward facing once the child reaches a certain weight (35 pounds in the United States). In Europe, seat choices include group 0+ (birth to 13 kg) and rear-facing group 1 (9–18 kg) seats (Watson & Monteiro, 2009). Infants and toddlers should always ride in the back seat. A rear-facing child should never be restrained in front of an active air bag because this is likely to be fatal in the event of a crash (Williams & Croce, 2009). In some localities, it is illegal to place a rear-facing seat in the front seat of a vehicle with an active air bag. The safety seat should be installed with the safety belt or child restraint anchors locked tight in position so that the seat will not move more than an inch when pulled from side to side or from the front (NHTSA, 2007). The harness straps must be routed according to instructions and positioned snugly (i.e., do not allow any slack but do not press too hard into the child's body), with the retainer (chest) clip positioned at armpit level. Harness straps should be routed at or below shoulders when rear facing to keep the child down and in the protective shell of the seat in the event of a crash.
In the United States, seats are not routinely tethered when in the rear-facing position (NHTSA, 2007). However, throughout Europe, Australia, and Canada, seats are tethered in the rear-facing position (NHTSA, 2007). Top tethers provide a third point of attachment to the vehicle and decrease forward head movement in a crash by 4–6 in. (NHTSA, 2007). Among countries that do tether rearward-facing seats, there is some dissention regarding the best method of tethering.

5.2.2. Stage 2: Forward-Facing Seats with Harness Systems

Toddlers and preschoolers should ride forward facing from approximately age 2 years and at least 20 pounds to approximately age 4 and 40 pounds in a seat equipped with a harness system (NHTSA, 2007). Again, children should remain rear facing as long as possible to the maximum rear-facing weight limit for the seat. Similarly, it is important that children remain in safety seats with harness straps until at least 40 pounds or to the maximum weight limit for harness straps. Parents are dissuaded from graduating children to a booster seat until at least 40 pounds (or later, if possible, given higher harness weight and height limits). Harnesses are important for keeping a child's small body properly positioned in the seat and distributing crash forces over the strongest parts of the child's body (NHTSA, 2007).
Toddlers and preschoolers have a variety of seat options with a multitude of height/weight specifications, including convertible seats that face rearward or forward, standard forward-facing seats, and combination toddler/booster seats that convert from a harnessed seat to a booster seat. The rear-facing weight range is generally 5–35 pounds for convertible seats in the United States. Upper harness weight limits for forward-facing configurations vary greatly by type of seat and range from 40 to 80 pounds in the United States.
The safety restraint should be installed with the safety belt or child restraint anchors locked tight in position so that the seat will not move more than an inch when pulled from side to side or from the front (NHTSA, 2007). The use of a top tether, positioned snugly, is highly recommended (and required in many countries) due to the resulting decrease in forward movement and head excursion during a crash (NHTSA, 2007). The harness straps must be routed according to instructions and positioned snugly (i.e., do not allow any slack but do not press too hard into the child's body), with the retainer (chest) clip positioned at armpit level. To keep the child positioned snugly in the seat during a crash, harness straps should be routed at or below shoulders when rear facing and at or above shoulders when forward facing.

5.2.3. Stage 3: Booster Seats

Once children outgrow traditional safety seats, belt-positioning booster seats are recommended prior to transitioning to safety belts alone. Booster seats are used in combination with the vehicle's lap/shoulder safety belt system. The odds of motor vehicle crash injury to children aged 4–8 years are 45% lower when riding in belt-positioning booster seats than when riding in seat belts alone (Arbogast et al., 2009). The booster seat's primary function is to raise the child higher so the vehicle belt system fits correctly over strong bony parts of the body, with the lap portion low on the hips and the shoulder belt snug across the chest and shoulder (NHTSA, 2007). Without a booster seat, a safety belt's positioning over soft and vulnerable parts of the body increases the risk of abdominal, neck, and spinal cord injuries (collectively known as “seat belt syndrome”) in a crash (Arbogast et al., 2009; NHTSA, 2007). Furthermore, the risk for brain injury is increased when a child places a poorly fitting shoulder belt behind his or her back for comfort because the child's head is likely to strike his or her knees or the vehicle interior during a crash (Arbogast et al., 2009 and Winston and Durbin, 1999). Despite the risks to children prematurely graduated to safety belts, studies have found that many parents of booster-age children do not own a booster seat, and most are misinformed about recommendations for booster seat use (Eby et al., 2005, Greenspan et al., 2010, Lee et al., 2008, Simpson et al., 2002 and Winston et al., 2004). Lags in policy further complicate the confusion for parents (Partners for Child Passenger Safety, 2007 and Ross et al., 2004).
Booster seats are recommended for use until a child grows to approximately 4 feet 9 inches tall and 80 pounds, and graduation to a belt is best determined by proper fit of the safety belt on the seated child (NHTSA, 2007). Specifically, children are not ready for an adult safety belt until they can (1) sit all the way back in the vehicle seat; (2) with knees bent comfortably at the edge of the seat; (3) the shoulder belt crossing the middle of the chest and resting at the shoulder (not the neck); (4) the lap belt fitting low and snug on the hip bones, touching the upper thighs (not the stomach); and (5) stay seated like this for the entire trip. Most children require a booster seat until at least 8 years of age, and many small-frame youngsters will require a booster long past the age of 8 years. For this reason, some countries commonly recommend the use of booster seats up to age 10 or even 12 years, unless the child surpasses height recommendations.
As with all children younger than age 13 years, children in this age group should always ride in the back seat. Both high-back and no-back boosters are available. High-back boosters are useful in vehicles that do not have headrests or have low seat backs. Backless boosters are usually less expensive and are easier to move from vehicle to vehicle. Backless boosters can be safely used in vehicles with headrests and high seat backs (Arbogast et al., 2009). Many high-back boosters are actually combination seats that come with harnesses that can be used for smaller children and can then be removed for older children. Lap and shoulder belts are required with booster seats because the shoulder belt is necessary to minimize forward movement of the torso and keep the child in position (NHTSA, 2007). There are some alternatives for vehicles with only lap belts, including having shoulder belts installed in the vehicle, using a safety seat with a harness system that goes up to high weights (e.g., 80 pounds), or using a travel vest.

5.2.4. Stage 4: Lap/Shoulder Safety Belts

Older children should travel in a lap and shoulder safety belt system once they outgrow a booster seat, which is usually after they reach approximately 80 pounds or grow to 4 feet 9 inches tall. Again, proper fit of the belt system is the best determining factor for the timing of transition. The back seat is recommended for children younger than age 13 years.
“Tweens” (8- to 12-year-olds) and young teens (13- to 15-year-olds) are at high risk for crash injury given a propensity toward inconsistent restraint use and increased front seat positioning compared to their younger peers. Studies of tween and young teen belt use have reported that the rate of belt use is frequently well below rates observed for adults and younger children (Agran et al., 1998 and Greenspan et al., 2010; Will, Dunaway, Lorek, Kokorelis, & Sabo, 2010). Many tweens only sit in the back if told to do so by their parents, and most tweens in the United States (73%) sit in the front passenger seat when they are the sole passenger (Durbin, Chen, Elliott, & Winston, 2004). In the United States, twice as many 12- to 14-year-old children are unrestrained compared to 0- to 4-year-old children (Berg et al., 2000). Tweens and young teens are also at greater risk when traveling with teen drivers because they are less likely to wear their safety belt or sit in the back seat (Winston, Kallan, Senserrick, & Elliott, 2008).
Tweens and young teens are at an ideal age for intervention because they are highly impressionable and very susceptible to both peer and parent influences (Jennings, Merzer, & Mitchell, 2006). Furthermore, they are in a time of transition and are just starting to make their own decisions and develop safety habits. Unfortunately, the traffic safety field has few programs specifically targeting this age group, and as such, a significant gap exists in traffic safety programming.

5.2.5. Children with Special Health Care Needs

When considering developmentally appropriate restraints, it should be noted that some children may require special seats or positioning for a variety of medical conditions (O'Neil, Yonkman, Talty, & Bull, 2009). These sometimes include, but are not limited to, prematurity, low birth weight, orthopedic conditions, casts (including hip spica casts), cerebral palsy and other neuromuscular disorders, autism and related disorders, and Down's syndrome. Whenever possible, a caregiver should use a standard child restraint system to transport children with special health care needs. Lateral support and positioning can be achieved with rolled towels or blankets positioned around the child (O'Neil, Yonkman, et al., 2009). In some cases, the use of specialized medical seats may be necessary. Medical equipment should be secured to the floor or under the seat in front of the child. Caregivers should seek recommendations for safe transportation from physicians, nurses, and physical, occupational, or rehabilitation therapists (O'Neil, Yonkman, et al., 2009).

5.3. Rear Seating

Because frontal collisions are the most common type of crash, rear seating offers protective effects for children because they are farthest from the most common point of impact. Although age-appropriate restraints offer relatively more safety benefit than does rear seating, rear seating offers independent and additive safety protections in a crash (Berg et al., 2000, Braver et al., 1998, Durbin et al., 2005 and Lennon et al., 2008). Children (age 0–12 years) in the front seat are at 40% greater risk of injury compared to those seated in the back (Durbin et al., 2005). For 0- to 4-year-olds, death risk is two times greater in the front seat versus the back, and risk for serious injury is 60% greater (Lennon et al., 2008). For children younger than 1 year of age, the death risk is four times greater in front versus back seats (Lennon et al., 2008). Both restrained and unrestrained children are at a lower risk of dying in rear seats (Braver et al., 1998, Durbin et al., 2005 and Lennon et al., 2008).
In the United States, one-third of children younger than age 13 years sit in the front seat (Durbin et al., 2004). Incidence of riding in the front seat increases with age, with most children older than age 8 years being seated in the front seat (Durbin et al., 2004 and Greenspan et al., 2010).

5.3.1. Dangers of Supplemental Restraint Systems

Supplemental restraint systems (air bags) have increasingly been incorporated in passenger vehicles in many areas of the world since the 1990s. Supplemental restraint systems operate by crash-detection sensors and inflate instantly to provide a barrier between the occupant and objects in the direction of the collision. Air bag systems are intended to supplement the use of safety belts and restraints, which are necessary to keep the occupants in position as the air bags inflate and provide protection. For adults, air bags are associated with a reduced risk of mortality and decrease in injury severity (Williams & Croce, 2009).
Despite their protective benefits for adults, frontal air bags pose great risk to children seated directly in front of them due to the speed and force with which they deploy (Williams & Croce, 2009). Rear-facing children, especially, can endure fatal head, neck, and spinal cord injuries from frontal air bags (NHTSA, 2007; Williams & Croce, 2009).
In response to the dangers to children, small adults, and unrestrained occupants, frontal air bag designs were depowered in 1998 to deploy at slower speeds. Although the redesign successfully reduced air bag-related mortality risk to children, frontal air bags remain unsafe for children (Arbogast et al., 2005 and Williams and Croce, 2009). Thus, children younger than age 13 years should never be seated in front of an active air bag. To further mitigate risk to children, advanced air bags have been introduced on some vehicle models that automatically turn off when a child or small adult is detected in the seat.
Side-impact, curtain, and rollover air bags pose less risk than frontal air bags to children due to the manner in which they deploy. Additional research is needed to determine the relative risks and benefits of side-impact and overhead air bags to children. Tentatively, it appears they do not pose great risk and may provide extra protection, provided the child is not leaning against them or otherwise out of position when they inflate (NHTSA, 2007).

5.4. Additional Challenges and Barriers to Occupant Protection

5.4.1. Factors Associated with Children's Restraint Use

A number of factors have been found to correlate with non-use of appropriate restraints for children. Appropriate restraint use for children is decreased (1) among older children; (2) with increasing number of occupants; (3) in older vehicles, pickup trucks, and large vans; (4) in rural areas; (5) with unbelted drivers; (6) with young drivers; (7) with drivers older than age 60 years; and (8) with alcohol use (Agran et al., 1998, Eby et al., 2005, Greenspan et al., 2010, Lee et al., 2008 and Winston et al., 2008). U.S. researchers have also noted differential use by other demographic subgroupings, including race and ethnicity (Lee et al., 2008). Driver restraint use is the strongest predictor of children's use of appropriate restraints (Agran et al., 1998 and Eby et al., 2005).

5.4.2. Misuse

Studies in the United States have shown that approximately three out of four safety restraints are unintentionally misused, and critical misuse of a restraint can reduce its effectiveness against severe injuries (Arbogast and Jermakian, 2007, Decina and Lococo, 2005, Decina and Lococo, 2007 and Dukehart et al., 2007; O'Neil, Daniels, et al., 2009). Misuse is caused by a number of factors. As evidenced previously, the age and weight stipulations, variety of seat options, and vehicle placement stipulations vary widely. Also, at any given time, there are more than 100 different models of child safety seats, approximately 300 models of passenger vehicles, and at least 27 different seat belt systems. Therefore, it is not surprising that fitting a safety seat in a vehicle is often confusing to parents.
Certain installation problems may seem like minor adjustments to parents, but they are vital for preventing ejection and for distributing crash forces across the strongest points of children's bodies. The three most common errors parents make when installing their children's seats are failure to (1) attach the seat tightly to the vehicle, (2) fasten the harness tightly, and (3) position the harnesses correctly (Decina and Lococo, 2005 and Dukehart et al., 2007). Failure to secure a child seat tightly and properly to the vehicle permits excessive movement of the restraint in a crash and often results in head injuries as the child contacts parts of the vehicle's interior (NHTSA, 2007).
To combat misuse, three-point universal safety seat attachment mechanisms (e.g., Lower Anchors and Tethers for Children or universal anchorage systems) are increasingly incorporated on new vehicles and safety seats manufactured in many areas of the world (NHTSA, 2007). Allowing parents to simply “click” the safety seat in place, the safety seat anchor systems are meant to combat one of the most common and serious installation errors—failing to attach the safety restraint tightly to the vehicle. However, only those caregivers with both a new vehicle and a new safety seat benefit from the mechanism, and the system does not address the many other errors that can occur when positioning a child in a safety seat. Furthermore, evidence is mounting that universal attachment systems are still prone to misuse (Arbogast and Jermakian, 2007 and Decina and Lococo, 2007).
Misuse of restraints is not limited to traditional safety seats. The misuse rate for belt-positioning booster seats is between 40 and 65%, and is related primarily to misrouting of the safety belt (Decina & Lococo, 2005; O'Neil, Daniels, et al., 2009). Furthermore, a study in the United States found that one-fifth of 8- to 12-year-old children did not use shoulder belts, placing them at a 1.8% higher risk of injury compared to those using both lap and shoulder belts (Garcia-Espana & Durbin, 2008). Common misuses of booster seats and safety belts alike include the shoulder belts being positioned behind the child's back, under the child's arm, over the booster seat armrest, not at mid-shoulder position, and too loosely (Decina & Lococo, 2005; O'Neil, Daniels, et al., 2009).

5.4.3. Caregiver Naïvveté and Complacency

Misuse and non-use of safety restraints involves a complex interplay of determinants, including, but not limited to, perception of risk, parenting style, and personal beliefs (Bingham et al., 2006, Simpson et al., 2002, Will, 2005, Will and Geller, 2004 and Winston et al., 2007). Safety advocates are presented with both challenges and opportunities for promoting proper restraint use. On the one hand, recommending the use of a safety restraint is a relatively straightforward recommendation (compared to, for example, losing weight or quitting smoking), which results in dramatic improvements in safety. On the other hand, caregivers often struggle with low perceptions of risk, poor recognition of restraint system effectiveness, flawed understanding of crash forces, and a number of other competing factors such as child protest and legal loopholes.
Motor vehicle travel is familiar, occurs in a well-understood system, permits one to feel in control while behind the wheel, has the added perk of convenience, and disperses injuries and deaths over time and space. Research has shown that all of these characteristics of motor vehicle travel lead to reduced perception of risk (Sandman, 1991, Slovic, 1991 and Will and Geller, 2004). Consequently, caregivers struggle with an immunity fallacy, or a reduced perception of personal or familial risk for injury in a crash (Will, 2005). This is unfortunate because risk communication research and other health behavior theories demonstrate that recognition of personal vulnerability to a hazard is a necessary prerequisite to behavior change (Bandura, 1986, Sandman, 1991, Slovic, 1991 and Weinstein, 1988).
Stage models such as the precaution adoption process model (PAPM; Weinstein, 1988) and transtheoretical model (Prochaska, 1979 and Prochaska et al., 1998) remind us that it is important to examine whether or not a health message is appropriate for the audience. Stage models provide a framework for understanding how individuals progress toward, adopt, and maintain behavior change. For instance, the PAPM includes both an “unaware” stage, in which individuals are not informed of the problem, and an “unengaged” stage, in which individuals can be fully informed of the problem but not motivated to do anything about it (Weinstein, 1988). This is often due to low recognition of personal vulnerability. The combination of many factors leaves many caregivers in the unengaged stage of the PAPM.
A key assumption of stage models is that interventions should be matched to the audience's stage (or readiness for change) to achieve maximum results (Prochaska, 1979, Prochaska et al., 1998 and Weinstein, 1988). Education-only messages common in child passenger safety are only appropriate for caregivers in the unaware stage of the PAPM. Unengaged caregivers are unlikely to read a brochure (even one handed to them), watch a video on their own, or attend a safety event for the issue. Information and education is absolutely necessary and beneficial, especially considering so many caregivers are uninformed regarding safety recommendations—but information is only effective if parents attend to it and find it personally applicable. If much of the audience is in the unengaged stage, then our task as public health professionals is to design better interventions to stir attention and motivate action (not just educate). This will not only mean enhancing the message in accordance with theories of behavior change and risk communication but also changing the intervention approach from passive (where caregivers must seek out the intervention) to more progressive (where caregivers are intervened upon) (Trifiletti et al., 2005 and Will et al., in press).

5.5. Recommended and Empirically Supported Interventions for Child Passenger Safety

Recommended and empirically supported interventions for child passenger safety include laws, enforcement, and educational campaigns that are enhanced with an intervention modality to improve motivation (Dellinger et al., 2007, Dinh-Zarr et al., 2001, Turner et al., 2005 and Zaza et al., 2001). A fairly comprehensive review of interventions for occupant protection by level of evidence was completed for the Handbook of Injury and Violence Prevention (Dellinger et al., 2007). Although Dellinger and colleagues' main conclusions are summarized here, the reader is referred to their chapter for additional details on specific intervention strategies and studies included in their review.
Laws regulating child passenger safety are among the most effective mechanisms for decreasing childhood crash injuries among the masses (Bingham et al., 2006, Dellinger et al., 2007, Dinh-Zarr et al., 2001, Partners for Child Passenger Safety, 2007, Winston et al., 2007 and Zaza et al., 2001). However, laws must be well publicized, comprehensive, and understood (Sleet, Schieber, & Gilchrist, 2003). Combining results from a variety of intervention studies, child safety seat laws are associated with a median 13% increase in child safety seat use and a median 17% decrease in fatal and nonfatal injuries (Dellinger et al., 2007). Safety belt laws are also associated with increased use (median of 33%) and decreased fatalities and injuries (median decreases of 9 and 2%, respectively) (Dellinger et al., 2007).
Primary enforcement laws (allowing an officer to stop a vehicle solely for a restraint use violation) have stronger evidence of support than do secondary enforcement laws (Dellinger et al., 2007 and Dinh-Zarr et al., 2001). Enhanced enforcement programs combine enforcement of restraint use violations at specific locations and times with pre-publicity about the enforcement effort (Dellinger et al., 2007). Such programs, including the U.S.-based Click It or Ticket, are associated with reductions in injury rates and a median 16% increase in observed safety belt use (Dellinger et al., 2007).
Enhanced education campaigns combine education with an intervention modality to improve motivation. Recommendations with strong or sufficient evidence for effectiveness include education plus enforcement, education plus incentives, and education plus distribution programs (Dellinger et al., 2007).
Communitywide information plus enforcement campaigns use mass media mailings and public information displays to promote use, combined with special enforcement strategies such as checkpoints to enforce child seat use laws (Dellinger et al., 2007). Education plus enforcement strategies are associated with a median increase in child safety seat use of 12% (Dellinger et al., 2007).
Education plus incentive programs provide rewards to children and parents for purchasing and using child safety seats, coupled with education regarding child passenger safety (Dellinger et al., 2007 and Ehiri et al., 2006). Education plus incentive programs are frequently implemented in day care centers and communitywide, and they are associated with a median 10% increase in child safety seat use (Dellinger et al., 2007).
Education plus distribution programs provide education and safety seats to parents through loans, low-cost rentals, or giveaways. Education and distribution programs are associated with a median 23% increase in possession of and proper use of safety seats (Dellinger et al., 2007). Successful education and distribution programs have been implemented by a variety of agencies, including hospitals and clinics, as part of postnatal home visits, and by auto insurance companies (Dellinger et al., 2007, Ehiri et al., 2006, Johnston et al., 2000, Kedikoglou et al., 2005 and King et al., 2005).
Although there is currently not a sufficient body of evidence to draw definitive conclusions, empirically supported education plus risk communication programs are also emerging as a fourth type of enhanced education campaign. The emerging education plus risk communication programs are solidly grounded in theory and incorporate targeted components for key health behavior concepts such as risk perception, vulnerabilities, fear, self-efficacy, and readiness for change (Erkoboni et al., 2010 and Will et al., 2009; Winston, Erkoboni, et al., 2007).
There is insufficient evidence concerning the effectiveness of education-only programs, but these programs may increase knowledge and thus be a predisposing factor for other interventions (Dellinger et al., 2007 and Zaza et al., 2001). Hands-on education at child passenger safety checkup events has been shown to increase correct use of safety restraints (Dukehart et al., 2007).
Finnegan and Viswanath (1997) recommend using multiple strategies to aim for synergy among interventions because each strategy has weaknesses. For instance, group-intensive interventions plus mass media can help to overcome knowledge gaps, particularly when media coverage is designed to increase perception of risk. A number of multicomponent community-based interventions have been employed, and these often combine multiple empirically supported strategies (e.g., legislation with targeted or mass media education) (Ekman et al., 2001 and Turner et al., 2005). Other interventions have found success with school-based multicomponent programming (Floerchinger-Franks, Machala, Goodale, & Gerberding, 2000; Will et al., 2010; Williams, Wells, & Ferguson, 1997). However, few comprehensive community-based studies have employed sound designs and rigorous evaluation methods (Klassen et al., 2000 and Turner et al., 2005).

6. Conclusions

Children are especially susceptible to road traffic injury, and morbidity and mortality rates throughout the world reflect this vulnerability. The interplay of a dangerous roadway environment and children's developmental limitations has led to road traffic injury being one of children's greatest threats to health and well-being. In the push toward global intervention on behalf of road traffic injury among children, ample logistical questions are yet to be answered. The United Nations and World Health Organization note a number of pertinent research and policy needs that are important for the advancement of global efforts (Peden et al., 2008, Peden et al., 2004, World Health Organization, 2009 and World Health Organization, 2010). Chief among these is a prioritization of children's needs when planning transport projects. Also important are implementing engineering measures, improving vehicle design standards, increased use of safety equipment, enacting legislation and standards, developing education and skills, and improving emergency and trauma care (Peden et al., 2008). More frequent and sophisticated applications of behavioral and social science theory, more rigorous evaluation methodologies, and increased funding for these scientific investigations are needed in the field of injury control. Focused global coordination and intervention is urgent and paramount to reverse the trend toward road traffic injury becoming the number one cause of death and disability for children.
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