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Rearward-facing child seats—The safest car restraint for children?
Accid.
And. & Rev. Vol. 23. Nos. 213. pp. 175-182.
1991
o@x-4575/91 $3.00+ .olJ 0 1991 Pergamon Press plc
Printed in Great Britain.
REARWARD-FACING CHILD SEATS-THE SAFEST CAR RESTRAINT FOR CHILDREN? GERD
CARLSSONand HANSNORIN
Volvo Car Corporation,
Goteborg,
Sweden
LARS YSANDER Varberg Hospital, Varberg, Sweden (Received 27 July 1989) Abstract-During recent years the use of child restraints in cars in Sweden has rapidly increased. The fact that the different restraint systems prevent injuries has been substantiated; as is shown in this paper. The major emphasis is put on the benefits of using rearward-facing child seats for children 0 to 4 years of age. Attitudes concerning child safety in cars and the misuse problem are also discussed. Based on Votvo’s accident material it is shown that the inju~-reducing effect of the rearward-facing child seat is superior to all present types of child restraints in cars. This paper is mainly based upon Volvo’s own traffic accident material. This paper is based upon accidents that occurred between the years 1976 and 1988 and comprises some 13,000 accidents involving approximately 22,OCflpeople. In 1,500 of these accidents at least one child (0 to 14 years) was present in the vehicle. In addition to the collection of accident data, separate attitude studies have been carried out, concerning child safety in cars.
HISTORY
OF CHILD
RESTRAINTS
IN SWEDEN
Using the principles involved in space research to protect the astronauts against injuries from the high level of acceleration during takeoff, Aldman designed a rearward-facing child seat in 1964. The purpose of this seat was to distribute the forces of a frontal collision over a large part of the child’s body, i.e. the entire back, neck, and head, and also to provide support to the spine during the course of an accident. This is especially important for small children, since a conventional forward-facing restraint system can not provide sufficient support to the child’s disproportionally large head and weak neck during a forward collision (Aldman 1966). The first rearward-facing child seat was intended for children between 9 months and 4 years old and was on sale in Sweden at the end of the 1960s. A few years later the first rearward-facing infant seat was introduced on the United States market, the General Motors Infant Love Seats. Today the rearward-facing infant seat is accepted as the safest way for infants to travel and is used in many parts of the world. However, rearward-facing child seats for children above infancy, i.e. in the group 1 to 4 years, are mostly found in Scandinavia. As soon as the rearward-facing child seats were introduced onto the Swedish market, they were recommended by the Swedish Traffic Safety Authority. A few years later, in 1973, regulations were introduced for the approval of child restraint systems in Sweden. These requirements were so strict that only rearward-facing child seats were approved. There are two types of rea~ard-facing child seats in Sweden: (i) infant seafs for children from 0 to approximately 6 months-these seats can be located in the car’s front or back seat and are fitted in the car with the ordinary adult seat belt of the car; (ii) toddler seats for children from 6 months to approximately 4 years-these are used mainly in the front seat and supported also by the dashboard, which is a part of the restraint system. The toddler seats are most often fitted in the car with the adult seat belt and an extra strap that provides firm positioning.
175
G. CARLSSON et al.
176
MODE
OF TRAVEL
Rearward-facing child seats began to make an impact at the end of the 1970s. In 1988, 40% of all children aged between 0 and 4 years travelled in rearward-facing child seats (see Fig. 1, showing the use of various child restraints, 1976-1988). A large proportion (70%) of the youngest children travelled unrestrained in cars up to the end of the 1970s. At the beginning of the 1980s we noticed a significant increase in the use of different restraint systems. This increase has continued successively and has meant that today almost all children aged 0 to 4 years who travel in Volvo cars in Sweden are restrained. The reasons for the rapid increase during the last few years are many. During the first part of the 1980s an intensive effort was made to make people aware of the importance of being restrained in cars-this applied to adult occupants as well as children. A few examples of these efforts are various types of campaigns, the loaning of infant seats to parents with newborn babies, and in 1987, a restraint use law for children. The use of carrycots was common when travelling with infants in a car up until 1980 and was also recommended by the authorities in Sweden. At the beginning of the 1980s rearward-facing infant seats were introduced in Sweden and to a large extent replaced the carrycot. The booster cushion was introduced in Sweden in 1978 and a few years later the booster seat (with backrest). The booster cushion/seat and the child are together restrained by the adult seat belt. It is recommended for children between 4 and 10 years. Almost 50% of the younger children use booster cushions/seats. The ordinary three-point or two-point adult seat belt was a relatively common protection system also for younger children in the beginning of 1980, but has become more uncommon because the restraint use law for children states that up to the age of 6 years children must travel in a separate child restraint system. Misuse
Misuse can be referred to as partial misuse or gross misuse. Partial misuse means incorrect use of a child restraint,-e.g. the child is not properly restrained or has the
90 80 70 60 50 40
Rearward - facing child seat
30
Booster seat/cushion 20
!
Seat belt
I
Cartycot
I ,
10
r .
Unrestrained
I , I
0
1
82838485868789 Fig. 1. Mode of travel for children in the age group 0 to 4 years divided into accident years, Sweden. (Volvo’s accident material).
Rearward-facing
child seats
117
size or age for the seat used. Gross misuse means incorrect mounting or no mounting of the child seat, or the child not restrained in the seat. According to data from the United States, between 50% and 75% of all child seats are used incorrectly. A correctly used child seat helps reduce the risk of fatal injuries by approximately 70%) whilst the corresponding figure for a partially misused child seat is approximately 40% (Petrucelli 1986). Since rearward facing child seats are used in a limited market-mainly in Scandinavia-there are few investigations that deal with misuse of rearward-facing child seats, i.e. for children above infancy. Special questions were put to people who had children in the car at the time of the accident. Typical questions were: Was the child seat installed according to instructions? Did it become loose during the accident? Was the child restrained in the seat? Was the child injured? Of the 142 rearward-facing child seats, 9 (6’3’ o) were used incorrectly. The most common type of misuse was that the seat was not fitted according to the instructions. In two cases the child seat was fitted facing forwards. In one of these cases the child sustained fatal head injuries when the roof intruded into the compartment where the child was sitting. It is not clear, however, whether the child was restrained in the seat or not. In the other eight cases misuse did not lead to injuries to the child, not did the seat become loose during the accident. The misuse figure from the above study is probably somewhat conservative, since parents do not always know whether they have installed the seat correctly. Studies of road traffic in Sweden have been carried out in order to detect the magnitude and type of misuse of child restraints. These studies, however, include a limited number of rearward facing child seats-a total of 22. Of the 22 seats, 10 were used incorrectly. The author concludes that the seat was not always anchored to the car correctly, but mostly facing the wrong direction, i.e. the child was facing forward, and the seat was not properly anchored to the car (Tingvall 1987). From the studies above, it is not possible to draw any reliable conclusions regarding the number of misused rearward-facing child seats, but it is probably much less than the corresponding number for forward-facing seats. Furthermore, misuse of rearward-facing child seats may not always result in serious injury, and this is substantiated by the obvious reduction in the number and degree of injuries with rearward-facing seats fitted.
wrong
INJURIES
In this section, the injury rate and injury type for restrained and unrestrained children in the age group 0 to 4 years are highlighted. The severity of injuries is described according to the internationally accepted Abbreviated Injury Scale (AIS). According to AIS the degree of severity of an injury varies from the value of 1 (minor injury) to the value 6 (fatal injury). Injury rate
The children have been divided into three groups (Table 1). Group 1, “rearward facing child seat ,” includes children in both infant and toddler seats. Group 2, “booster cushion/seat,” includes children who used a booster cushion in combination with an adult seat belt, mainly three-point. The third group, “unrestrained children,” comprises all other modes of travel, e.g. unrestrained on normal seating
Table I. Children grouped according to restraint used Tvoe of restraint used
Number of children
1. Rearward-facing child seat 2. Booster cushion/seat 3. Unrestrained
142 130 228
178
G. CARLSSON et al.
positions, sitting on an adult’s lap, or lying or standing in the car. Children using a seat belt only are excluded from further analysis, since they make up a limited number-39 cases. Figure 2 shows the injury rate for different modes of travel for children 0 to 4 years. As can be seen in Fig. 2, children who travel in rearward-facing child seats have the lowest injury risk of slight as well as more serious injuries, whereas unprotected children have a considerably higher risk of injury than those in the protected groups. Children using booster cushions/seats have a higher injury rate than children in rearwardfacing child seats. Since there is no statistically significant difference in crash severity or in the distribution of accident types between the three groups of children, it is possible to estimate the effectiveness of the different child restraint systems in reducing Maximum Abbreviated Injury Scale (MAIS) l-6 and MAIS 2-6 injuries. The effectiveness (e) can be defined as e = injury rate, unrestrained
- injury rate, restrained.
As we can see, the effectiveness of the rearward-facing child seat of reducing injuries is very high (Table 2). Types of injury. In Table 3 the injury rate (MAIS 1-6, MAIS 2-6) for different body regions are presented for restrained and unrestrained children. Most noticeable is the difference in head injury rate between unrestrained and restrained children. The use of restraint significantly reduces both slight and severe head injuries, especially in the case of children in rearward-facing child seats. Children using booster cushions/seats have a higher rate of neck and chest injuries than unrestrained children. However, only one of these injuries was more severe than AIS 1, this being an AIS 2 injury to the throat. Unrestrained children have a higher rate of limb injury, and also more severe injury, than restrained children. ATTITUDES-CHILDREN
IN CARS
Studies dealing with experience and attitude regarding the use of child seats show adult attitudes. The question is, how well do the adult answers reflect the actual experiences of the children? Volvo has carried out two attitude surveys concerning children in cars. One survey was carried out in 1978 amongst 700 company car owners at Volvo Goteborg, who had children under 15 years of age. The other survey was carried out in 1988 amongst 300 people who use Volvo’s child seat.
[7 MAIS 2-6
q MAlS1-6 Reatwardfacing child seat Fig. 2. Injury rate for restrained
Booster cushion/seat + seat belt
Unrestrained
and unrestrained children material).
0 to 4 years old. (Volvo’s accident
Rearward-facing
child seats
179
Table 2. Effectiveness of child restraints Injury reducing effect
Rearward-facing child seat Booster cushion/seat
MAIS 1-6
MAIS 2-6
76% 34%
92% 60%
These surveys indicated, among other things, the following problems for children in rearward-facing seats; (one child can, of course, have more than one problem): difficult to sit still, 30%; difficult to sleep in the seat, 8%; cannot see out, 5%; problems with the seat’s belt, (e.g. child opens the lock, the belt becomes tangled), 3%; feel sick, 2%. These results indicate that the greatest problem in connection with the use of the child seat is that the child does not want to sit still in the seat, especially during long trips. This problem is also found, with the same magnitude, in the above-mentioned study of forward-facing child seats. Other problems, such as difficulty of sleeping in the seat, not being able to see through the window, and problems with the seat’s belt are relatively small and also occur in forward-facing systems. In a study by Arnberg (1978) regarding problems in connection with the use of child seats, similar results were presented. The list of problems also shows that car sickness related to children in rearward-facing seats is a small problem. This has also been shown by Arnberg (1978) and Aldman (1966). In a study carried out on the Washington Metro Rail System (Trinkoff 1985), observations were made regarding how adults and children travelled. It showed that 66% of all children, but only 25% of adults preferred to travel facing backwards whilst travelling on the Metro. A conclusion from this study is that children seemed to choose to travel facing backwards, whilst the adults preferred to travel facing forward. Adults seem to have a resistance to travelling facing backwards, which can be one of the reasons why they have a misconception regarding the experience of children. An important reason why rearward-facing child seats are not used outside Scandinavia seems to be that it is considered awkward to install due to the fact that an extra fitting point is often required to provide a firm positioning. Arnberg (1978) investigated Table 3. Injury rate (%) (MAIS 1-6, MAIS 2-6) for different body regions for restrained and unrestrained 0- 4-year-old children. (Volvo’s accident material)
restrained
MAIS
2-6
G. CARLSON
180
et al
the attitude of parents in Sweden towards the installation of rearward-facing child seats. Nearly all of the parents who did got have a child seat thought that it was important that it should be easy to install, whereas those who did have a child seat rarely encountered problems with installation. ILLUSTRATIVE
ACCIDENTS
Since frontal collisions make up about half of all collisions resulting in serious or fatal injuries, a rearward-facing child seat will produce a large injury-reducing effect. The reason for this is that the forces developed in a frontal collision are distributed over the child’s back, neck, and head. In Volvo’s accident material there are a lot of frontimpact accident cases that clearly illustrate this effect. One typical example among these cases is described below. Accident case I The car in case 1 crashed head-on with another car. There was extensive deformation of the front of the vehicles (Fig. 3). The velocity change (delta v) is estimated to be 70-80 km/h. Travelling in the car were a belted driver who sustained serious injuries (AIS 3), two outboard rear seat passengers using three-point seat belts who sustained slight injuries (AIS 1). one middle rear seat passenger using a lap belt who sustained serious injuries (AIS 3) and one child in a rearward-facing child seat, right-hand front. The child in the child seat was the only uninjured person in the car in spite of the extensive deformations to the front of the vehicle. It is, of course, also of great importance that the child restraint functions well not only in frontal impacts but also in other types of accidents. Especially in the case of a rollover. there is a significant risk that an unrestrained child will be ejected from the car. Accident case 2 In accident case 2 the driver lost control of the vehicle, which ran off the road. The car continued down an embankment, rolled over several turns, and stopped at an un-
Fig. 3. Accident
case
I. Head-on
collision. Estimated velocity change 70-80 facing child seat located right-hand front.
km/h.
Child m a rearward-
Rearward-facing
Fig. 4. Accident
case 2. Rollover
accident.
child seats
Child in a rearward-facing
181
seat located
right-hand
front.
derpass, where it came to rest on its roof (Fig. 4). Travelling in the car were a belted driver who was uninjured, an unbelted rear seat occupant who sustained moderate injuries to the face, and a one-year-old child in a rearward-facing child seat in the right front seat. The child sustained no injuries.
CONCLUSIONS
AND
DISCUSSIONS
In this study the injury-reducing effectiveness of the rearward-facing child seat was estimated at 80%-90%, while the effectiveness of the forward-facing booster cushion/ seat was found to be 30%-60%. Nearly half the children in Volvo cars in Sweden aged between 0 and 4 years travel in rearward-facing child seats. The remaining restrained children travel facing forward, mainly on a booster cushion/seat. This is unfortunate since a forward-facing restraint system will not provide the same level of protection for children in this age group. During the 20 years in which rearward-facing child seats have been used in Sweden, only three children sitting in a rearward-facing child seat have died in a traffic accident. These fatalities occurred in accidents with extremely high crash severity. Today we can, for the most part, discard the myths, which have been compiled as motives against rearward-facing child seats. We believe that these myths. in certain cases, can be explained by adults’ misconceptions regarding the child’s experiences. The largest problem in connection with the use of both rearwardand forwardfacing child seats is that the child cannot sit still-especially during long trips. To make the child remain in the seat, it is therefore important that it can see and communicate with the other occupants in the car. If the driver is alone in the car. this can be achieved with a rearward facing child seat located in the front passenger seat. In order to achieve the most effective reduction of injuries to small children in car accidents, the safety design work should be aimed at developing rearward-facing child safety equipment. To make this possible, legislation and requirements should facilitate a development towards rearward-facing systems.
182
G. C~Rtssoi-4 et al.
REFERENCES Aldman, B. A protective seat for children. Experiments with a safety seat for children between one and six. Proceedings of the 8th Stapp Car Crash and Field Demonstration Conference. 320-328; 1966. Amberg, P. The design and effect of child restraint systems in vehicles. Ergonomics 21: 681-690; 1978. Petrucelli, E. The USA’s experience with child passenger safety. Proceedings of the Volvo/TN0 European Workshop on Child Safety in Passenger Cars, Kerkrade, The Netherlands; 1986. Tingvall, C. Children in cars. Acta Paediatr. Stand. Supplement 339: V:l-V:17; 1987. Trinkoff, A. M. Seating patterns on the Washington DC Metro rail system. Am. J. Public Health; 75(6): 657658; 1985.
And. & Rev. Vol. 23. Nos. 213. pp. 175-182.
1991
o@x-4575/91 $3.00+ .olJ 0 1991 Pergamon Press plc
Printed in Great Britain.
REARWARD-FACING CHILD SEATS-THE SAFEST CAR RESTRAINT FOR CHILDREN? GERD
CARLSSONand HANSNORIN
Volvo Car Corporation,
Goteborg,
Sweden
LARS YSANDER Varberg Hospital, Varberg, Sweden (Received 27 July 1989) Abstract-During recent years the use of child restraints in cars in Sweden has rapidly increased. The fact that the different restraint systems prevent injuries has been substantiated; as is shown in this paper. The major emphasis is put on the benefits of using rearward-facing child seats for children 0 to 4 years of age. Attitudes concerning child safety in cars and the misuse problem are also discussed. Based on Votvo’s accident material it is shown that the inju~-reducing effect of the rearward-facing child seat is superior to all present types of child restraints in cars. This paper is mainly based upon Volvo’s own traffic accident material. This paper is based upon accidents that occurred between the years 1976 and 1988 and comprises some 13,000 accidents involving approximately 22,OCflpeople. In 1,500 of these accidents at least one child (0 to 14 years) was present in the vehicle. In addition to the collection of accident data, separate attitude studies have been carried out, concerning child safety in cars.
HISTORY
OF CHILD
RESTRAINTS
IN SWEDEN
Using the principles involved in space research to protect the astronauts against injuries from the high level of acceleration during takeoff, Aldman designed a rearward-facing child seat in 1964. The purpose of this seat was to distribute the forces of a frontal collision over a large part of the child’s body, i.e. the entire back, neck, and head, and also to provide support to the spine during the course of an accident. This is especially important for small children, since a conventional forward-facing restraint system can not provide sufficient support to the child’s disproportionally large head and weak neck during a forward collision (Aldman 1966). The first rearward-facing child seat was intended for children between 9 months and 4 years old and was on sale in Sweden at the end of the 1960s. A few years later the first rearward-facing infant seat was introduced on the United States market, the General Motors Infant Love Seats. Today the rearward-facing infant seat is accepted as the safest way for infants to travel and is used in many parts of the world. However, rearward-facing child seats for children above infancy, i.e. in the group 1 to 4 years, are mostly found in Scandinavia. As soon as the rearward-facing child seats were introduced onto the Swedish market, they were recommended by the Swedish Traffic Safety Authority. A few years later, in 1973, regulations were introduced for the approval of child restraint systems in Sweden. These requirements were so strict that only rearward-facing child seats were approved. There are two types of rea~ard-facing child seats in Sweden: (i) infant seafs for children from 0 to approximately 6 months-these seats can be located in the car’s front or back seat and are fitted in the car with the ordinary adult seat belt of the car; (ii) toddler seats for children from 6 months to approximately 4 years-these are used mainly in the front seat and supported also by the dashboard, which is a part of the restraint system. The toddler seats are most often fitted in the car with the adult seat belt and an extra strap that provides firm positioning.
175
G. CARLSSON et al.
176
MODE
OF TRAVEL
Rearward-facing child seats began to make an impact at the end of the 1970s. In 1988, 40% of all children aged between 0 and 4 years travelled in rearward-facing child seats (see Fig. 1, showing the use of various child restraints, 1976-1988). A large proportion (70%) of the youngest children travelled unrestrained in cars up to the end of the 1970s. At the beginning of the 1980s we noticed a significant increase in the use of different restraint systems. This increase has continued successively and has meant that today almost all children aged 0 to 4 years who travel in Volvo cars in Sweden are restrained. The reasons for the rapid increase during the last few years are many. During the first part of the 1980s an intensive effort was made to make people aware of the importance of being restrained in cars-this applied to adult occupants as well as children. A few examples of these efforts are various types of campaigns, the loaning of infant seats to parents with newborn babies, and in 1987, a restraint use law for children. The use of carrycots was common when travelling with infants in a car up until 1980 and was also recommended by the authorities in Sweden. At the beginning of the 1980s rearward-facing infant seats were introduced in Sweden and to a large extent replaced the carrycot. The booster cushion was introduced in Sweden in 1978 and a few years later the booster seat (with backrest). The booster cushion/seat and the child are together restrained by the adult seat belt. It is recommended for children between 4 and 10 years. Almost 50% of the younger children use booster cushions/seats. The ordinary three-point or two-point adult seat belt was a relatively common protection system also for younger children in the beginning of 1980, but has become more uncommon because the restraint use law for children states that up to the age of 6 years children must travel in a separate child restraint system. Misuse
Misuse can be referred to as partial misuse or gross misuse. Partial misuse means incorrect use of a child restraint,-e.g. the child is not properly restrained or has the
90 80 70 60 50 40
Rearward - facing child seat
30
Booster seat/cushion 20
!
Seat belt
I
Cartycot
I ,
10
r .
Unrestrained
I , I
0
1
82838485868789 Fig. 1. Mode of travel for children in the age group 0 to 4 years divided into accident years, Sweden. (Volvo’s accident material).
Rearward-facing
child seats
117
size or age for the seat used. Gross misuse means incorrect mounting or no mounting of the child seat, or the child not restrained in the seat. According to data from the United States, between 50% and 75% of all child seats are used incorrectly. A correctly used child seat helps reduce the risk of fatal injuries by approximately 70%) whilst the corresponding figure for a partially misused child seat is approximately 40% (Petrucelli 1986). Since rearward facing child seats are used in a limited market-mainly in Scandinavia-there are few investigations that deal with misuse of rearward-facing child seats, i.e. for children above infancy. Special questions were put to people who had children in the car at the time of the accident. Typical questions were: Was the child seat installed according to instructions? Did it become loose during the accident? Was the child restrained in the seat? Was the child injured? Of the 142 rearward-facing child seats, 9 (6’3’ o) were used incorrectly. The most common type of misuse was that the seat was not fitted according to the instructions. In two cases the child seat was fitted facing forwards. In one of these cases the child sustained fatal head injuries when the roof intruded into the compartment where the child was sitting. It is not clear, however, whether the child was restrained in the seat or not. In the other eight cases misuse did not lead to injuries to the child, not did the seat become loose during the accident. The misuse figure from the above study is probably somewhat conservative, since parents do not always know whether they have installed the seat correctly. Studies of road traffic in Sweden have been carried out in order to detect the magnitude and type of misuse of child restraints. These studies, however, include a limited number of rearward facing child seats-a total of 22. Of the 22 seats, 10 were used incorrectly. The author concludes that the seat was not always anchored to the car correctly, but mostly facing the wrong direction, i.e. the child was facing forward, and the seat was not properly anchored to the car (Tingvall 1987). From the studies above, it is not possible to draw any reliable conclusions regarding the number of misused rearward-facing child seats, but it is probably much less than the corresponding number for forward-facing seats. Furthermore, misuse of rearward-facing child seats may not always result in serious injury, and this is substantiated by the obvious reduction in the number and degree of injuries with rearward-facing seats fitted.
wrong
INJURIES
In this section, the injury rate and injury type for restrained and unrestrained children in the age group 0 to 4 years are highlighted. The severity of injuries is described according to the internationally accepted Abbreviated Injury Scale (AIS). According to AIS the degree of severity of an injury varies from the value of 1 (minor injury) to the value 6 (fatal injury). Injury rate
The children have been divided into three groups (Table 1). Group 1, “rearward facing child seat ,” includes children in both infant and toddler seats. Group 2, “booster cushion/seat,” includes children who used a booster cushion in combination with an adult seat belt, mainly three-point. The third group, “unrestrained children,” comprises all other modes of travel, e.g. unrestrained on normal seating
Table I. Children grouped according to restraint used Tvoe of restraint used
Number of children
1. Rearward-facing child seat 2. Booster cushion/seat 3. Unrestrained
142 130 228
178
G. CARLSSON et al.
positions, sitting on an adult’s lap, or lying or standing in the car. Children using a seat belt only are excluded from further analysis, since they make up a limited number-39 cases. Figure 2 shows the injury rate for different modes of travel for children 0 to 4 years. As can be seen in Fig. 2, children who travel in rearward-facing child seats have the lowest injury risk of slight as well as more serious injuries, whereas unprotected children have a considerably higher risk of injury than those in the protected groups. Children using booster cushions/seats have a higher injury rate than children in rearwardfacing child seats. Since there is no statistically significant difference in crash severity or in the distribution of accident types between the three groups of children, it is possible to estimate the effectiveness of the different child restraint systems in reducing Maximum Abbreviated Injury Scale (MAIS) l-6 and MAIS 2-6 injuries. The effectiveness (e) can be defined as e = injury rate, unrestrained
- injury rate, restrained.
As we can see, the effectiveness of the rearward-facing child seat of reducing injuries is very high (Table 2). Types of injury. In Table 3 the injury rate (MAIS 1-6, MAIS 2-6) for different body regions are presented for restrained and unrestrained children. Most noticeable is the difference in head injury rate between unrestrained and restrained children. The use of restraint significantly reduces both slight and severe head injuries, especially in the case of children in rearward-facing child seats. Children using booster cushions/seats have a higher rate of neck and chest injuries than unrestrained children. However, only one of these injuries was more severe than AIS 1, this being an AIS 2 injury to the throat. Unrestrained children have a higher rate of limb injury, and also more severe injury, than restrained children. ATTITUDES-CHILDREN
IN CARS
Studies dealing with experience and attitude regarding the use of child seats show adult attitudes. The question is, how well do the adult answers reflect the actual experiences of the children? Volvo has carried out two attitude surveys concerning children in cars. One survey was carried out in 1978 amongst 700 company car owners at Volvo Goteborg, who had children under 15 years of age. The other survey was carried out in 1988 amongst 300 people who use Volvo’s child seat.
[7 MAIS 2-6
q MAlS1-6 Reatwardfacing child seat Fig. 2. Injury rate for restrained
Booster cushion/seat + seat belt
Unrestrained
and unrestrained children material).
0 to 4 years old. (Volvo’s accident
Rearward-facing
child seats
179
Table 2. Effectiveness of child restraints Injury reducing effect
Rearward-facing child seat Booster cushion/seat
MAIS 1-6
MAIS 2-6
76% 34%
92% 60%
These surveys indicated, among other things, the following problems for children in rearward-facing seats; (one child can, of course, have more than one problem): difficult to sit still, 30%; difficult to sleep in the seat, 8%; cannot see out, 5%; problems with the seat’s belt, (e.g. child opens the lock, the belt becomes tangled), 3%; feel sick, 2%. These results indicate that the greatest problem in connection with the use of the child seat is that the child does not want to sit still in the seat, especially during long trips. This problem is also found, with the same magnitude, in the above-mentioned study of forward-facing child seats. Other problems, such as difficulty of sleeping in the seat, not being able to see through the window, and problems with the seat’s belt are relatively small and also occur in forward-facing systems. In a study by Arnberg (1978) regarding problems in connection with the use of child seats, similar results were presented. The list of problems also shows that car sickness related to children in rearward-facing seats is a small problem. This has also been shown by Arnberg (1978) and Aldman (1966). In a study carried out on the Washington Metro Rail System (Trinkoff 1985), observations were made regarding how adults and children travelled. It showed that 66% of all children, but only 25% of adults preferred to travel facing backwards whilst travelling on the Metro. A conclusion from this study is that children seemed to choose to travel facing backwards, whilst the adults preferred to travel facing forward. Adults seem to have a resistance to travelling facing backwards, which can be one of the reasons why they have a misconception regarding the experience of children. An important reason why rearward-facing child seats are not used outside Scandinavia seems to be that it is considered awkward to install due to the fact that an extra fitting point is often required to provide a firm positioning. Arnberg (1978) investigated Table 3. Injury rate (%) (MAIS 1-6, MAIS 2-6) for different body regions for restrained and unrestrained 0- 4-year-old children. (Volvo’s accident material)
restrained
MAIS
2-6
G. CARLSON
180
et al
the attitude of parents in Sweden towards the installation of rearward-facing child seats. Nearly all of the parents who did got have a child seat thought that it was important that it should be easy to install, whereas those who did have a child seat rarely encountered problems with installation. ILLUSTRATIVE
ACCIDENTS
Since frontal collisions make up about half of all collisions resulting in serious or fatal injuries, a rearward-facing child seat will produce a large injury-reducing effect. The reason for this is that the forces developed in a frontal collision are distributed over the child’s back, neck, and head. In Volvo’s accident material there are a lot of frontimpact accident cases that clearly illustrate this effect. One typical example among these cases is described below. Accident case I The car in case 1 crashed head-on with another car. There was extensive deformation of the front of the vehicles (Fig. 3). The velocity change (delta v) is estimated to be 70-80 km/h. Travelling in the car were a belted driver who sustained serious injuries (AIS 3), two outboard rear seat passengers using three-point seat belts who sustained slight injuries (AIS 1). one middle rear seat passenger using a lap belt who sustained serious injuries (AIS 3) and one child in a rearward-facing child seat, right-hand front. The child in the child seat was the only uninjured person in the car in spite of the extensive deformations to the front of the vehicle. It is, of course, also of great importance that the child restraint functions well not only in frontal impacts but also in other types of accidents. Especially in the case of a rollover. there is a significant risk that an unrestrained child will be ejected from the car. Accident case 2 In accident case 2 the driver lost control of the vehicle, which ran off the road. The car continued down an embankment, rolled over several turns, and stopped at an un-
Fig. 3. Accident
case
I. Head-on
collision. Estimated velocity change 70-80 facing child seat located right-hand front.
km/h.
Child m a rearward-
Rearward-facing
Fig. 4. Accident
case 2. Rollover
accident.
child seats
Child in a rearward-facing
181
seat located
right-hand
front.
derpass, where it came to rest on its roof (Fig. 4). Travelling in the car were a belted driver who was uninjured, an unbelted rear seat occupant who sustained moderate injuries to the face, and a one-year-old child in a rearward-facing child seat in the right front seat. The child sustained no injuries.
CONCLUSIONS
AND
DISCUSSIONS
In this study the injury-reducing effectiveness of the rearward-facing child seat was estimated at 80%-90%, while the effectiveness of the forward-facing booster cushion/ seat was found to be 30%-60%. Nearly half the children in Volvo cars in Sweden aged between 0 and 4 years travel in rearward-facing child seats. The remaining restrained children travel facing forward, mainly on a booster cushion/seat. This is unfortunate since a forward-facing restraint system will not provide the same level of protection for children in this age group. During the 20 years in which rearward-facing child seats have been used in Sweden, only three children sitting in a rearward-facing child seat have died in a traffic accident. These fatalities occurred in accidents with extremely high crash severity. Today we can, for the most part, discard the myths, which have been compiled as motives against rearward-facing child seats. We believe that these myths. in certain cases, can be explained by adults’ misconceptions regarding the child’s experiences. The largest problem in connection with the use of both rearwardand forwardfacing child seats is that the child cannot sit still-especially during long trips. To make the child remain in the seat, it is therefore important that it can see and communicate with the other occupants in the car. If the driver is alone in the car. this can be achieved with a rearward facing child seat located in the front passenger seat. In order to achieve the most effective reduction of injuries to small children in car accidents, the safety design work should be aimed at developing rearward-facing child safety equipment. To make this possible, legislation and requirements should facilitate a development towards rearward-facing systems.
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G. C~Rtssoi-4 et al.
REFERENCES Aldman, B. A protective seat for children. Experiments with a safety seat for children between one and six. Proceedings of the 8th Stapp Car Crash and Field Demonstration Conference. 320-328; 1966. Amberg, P. The design and effect of child restraint systems in vehicles. Ergonomics 21: 681-690; 1978. Petrucelli, E. The USA’s experience with child passenger safety. Proceedings of the Volvo/TN0 European Workshop on Child Safety in Passenger Cars, Kerkrade, The Netherlands; 1986. Tingvall, C. Children in cars. Acta Paediatr. Stand. Supplement 339: V:l-V:17; 1987. Trinkoff, A. M. Seating patterns on the Washington DC Metro rail system. Am. J. Public Health; 75(6): 657658; 1985.