As noted in the viewpoint article by Kool et al in this issue of the NZMJ,1 injury remains the leading cause of death and disability for children beyond the perinatal period, with motor vehicle trauma accounting for a large proportion of the burden of disease.While there is broad consensus internationally that the risk of serious injury to children in car crashes can be substantially reduced by the correct use of a size-appropriate child restraint, many children continue to travel in the wrong restraint for their size, and many restraints are used incorrectly, greatly reducing their effectiveness.2 The key to helping parents and carers to correctly use the right restraint for their child on every trip is making it as simple as possible to follow best practice and changing the societal norms to be ‘best practice'.While raising the age for mandatory child restraint use is a step in the right direction, and will likely improve child restraint practices as it has done in Australia,3 choosing the 7th birthday as the upper age limit sends the message to parents that as soon as the child reaches their 7thbirthday, their child can stop using their booster seat even though they are not big enough to get good belt fit in an adult seatbelt 4,5 and are thus at higher risk of injury in a crash when using a seatbelt.As noted by Kool et al, since 2009 European law has required use of boosters up to the age of 12 years—demonstrating that more stringent legislation is practical. It also redefines best practice as the expected ‘norm'. Situations in which this is difficult to achieve in practice can be managed as exceptions to the general rule, in much the same way as children who are taller than 135–145 cm (depending on the country) are allowed to use seatbelts in Europe before 12 years of age. Similar approaches are used in Australia to allow for exemptions to the rear seating law for families with more young children than rear seating positions.Having the law require booster use up to age 12 also removes the general public perception that seatbelt use for children aged 7–12 is as safe as using a booster seat "because the law allows it" – a sentiment that is widely held by parents. Both New Zealand and Australia could learn from Europe's example.Another particular challenge in New Zealand is that it is difficult for parents to know when to transition their child from one restraint to the next, because these transitions are not defined clearly in the new law, and can be inconsistent between different restraints. This is difficult in any country due to the variation in the size of children at a given age, but this problem is greatly exacerbated in New Zealand because restraints certified to both US and European standards are accepted in addition to the joint Australian/New Zealand Standard, AS/NZS 1754.6 In contrast, only the joint Australian/New Zealand standard is accepted in Australia, and the child restraint law specifies a minimum age for use of each restraint type (e.g. 6 months for a forward-facing restraint, 4 years for a booster seat).While acceptance of restraints from all over the world certified to multiple standards appears to offer more choice to New Zealand families, these potential benefits are more than outweighed by the complexity of choosing the ‘best' restraint for a child, because different standards use different selection criteria (weight, age, height, shoulder height).Particularly confusing is that a child who fits one type of restraint under one system may not fit a similar type of restraint designed to another standard. For example, a three year old child may be in the weight range for a US certified booster seat but not be tall enough to fit in an AZ/NZS 1754 certified one. This encourages premature graduation to a booster seat via choice of the US restraint, while evidence shows the child is much safer staying in their forward-facing restraint than in a booster seat at this age.A good example of how to make restraint selection easy for parents is the new shoulder height marker system used on restraints certified under the Australian/New Zealand standard since 2010. These labels are placed on the restraint indicating the minimum and maximum shoulder heights for a child to fit properly in that restraint.These labels make it clear at a glance when a child fits into a particular restraint, because their shoulders must be between the two labels on the restraint. It discourages premature graduation because if a child is too small for the next restraint category, their shoulders will be below the minimum height label. This is a much simpler and more reliable way of choosing a restraint 7 than relying on the parent knowing the child's weight or height (many parents either do not know or their estimates are wildly inaccurate), and gives better fit of the child in a restraint, and therefore better protection in a crash.Another major safety concern is the continuing approval of child safety harnesses (or "H-harnesses") for use by children under 7 in New Zealand (www.nzta.govt.nz/traffic/students-parents/child-restraints.html), as research has shown that they can be particularly dangerous in crashes, and that they offer no benefit over lap-sash seatbelts.8Indeed the latest Australian/New Zealand Standard restricts their use to lap only seatbelts together with a booster seat that can stop the harness pulling up in a crash, allowing a child to slide under it. Children under 7 should not use harnesses without a booster seat. The recently published Australian National Guidelines for Child Restraint Use,9 which were approved by Australia's National Health and Medical Council in 2013, recommend against their use.The other critical aspect of child passenger safety is using restraints correctly. Incorrect use of restraints also substantially increases injury risk, by up to 7 times.10 Child restraint checking and fitting schemes have been shown to significantly reduce misuse,11 and the recommendation that parents make use of these schemes by the New Zealand Paediatric Society is valuable.Newer restraint installation systems, such as LATCH and ISOFIX can also reduce incorrect use. However, this is another area where the acceptance of multiple restraint standards in New Zealand makes parents lives much more difficult and potentially increases the risk of injury for New Zealand children, because different standards have different ways of installing restraints and different requirements for securing the child in the restraint. For example, top tether straps that connect the top of a child restraint to the car are highly effective in reducing injury, but their use on US and European restraints varies with the type of restraint and the type of installation system, while the joint Australian/New Zealand standard requires them for all infant and forward facing restraints, and many booster seats.Parents therefore know that all restraints require top tethers, rather than having to remember which restraint needs one. This is reflected in the substantially lower rates of top tether misuse seen in Australia than in the USA (~20% vs ~60%12,13).The bottom line is that we need to have a simple, consistent system for child restraint selection and use so parents can easily know what is ‘best practice' and how to achieve it. This requires design of legislation that sets the societal norms for restraint use to be equal to best practice, while allowing for exceptions as required to make it practical. These laws need to be supported by targeted education and child restraint fitting advice services.

As noted in the viewpoint article by Kool et al in this issue of the NZMJ,1 injury remains the leading cause of death and disability for children beyond the perinatal period, with motor vehicle trauma accounting for a large proportion of the burden of disease.While there is broad consensus internationally that the risk of serious injury to children in car crashes can be substantially reduced by the correct use of a size-appropriate child restraint, many children continue to travel in the wrong restraint for their size, and many restraints are used incorrectly, greatly reducing their effectiveness.2 The key to helping parents and carers to correctly use the right restraint for their child on every trip is making it as simple as possible to follow best practice and changing the societal norms to be ‘best practice'.While raising the age for mandatory child restraint use is a step in the right direction, and will likely improve child restraint practices as it has done in Australia,3 choosing the 7th birthday as the upper age limit sends the message to parents that as soon as the child reaches their 7thbirthday, their child can stop using their booster seat even though they are not big enough to get good belt fit in an adult seatbelt 4,5 and are thus at higher risk of injury in a crash when using a seatbelt.As noted by Kool et al, since 2009 European law has required use of boosters up to the age of 12 years—demonstrating that more stringent legislation is practical. It also redefines best practice as the expected ‘norm'. Situations in which this is difficult to achieve in practice can be managed as exceptions to the general rule, in much the same way as children who are taller than 135–145 cm (depending on the country) are allowed to use seatbelts in Europe before 12 years of age. Similar approaches are used in Australia to allow for exemptions to the rear seating law for families with more young children than rear seating positions.Having the law require booster use up to age 12 also removes the general public perception that seatbelt use for children aged 7–12 is as safe as using a booster seat "because the law allows it" – a sentiment that is widely held by parents. Both New Zealand and Australia could learn from Europe's example.Another particular challenge in New Zealand is that it is difficult for parents to know when to transition their child from one restraint to the next, because these transitions are not defined clearly in the new law, and can be inconsistent between different restraints. This is difficult in any country due to the variation in the size of children at a given age, but this problem is greatly exacerbated in New Zealand because restraints certified to both US and European standards are accepted in addition to the joint Australian/New Zealand Standard, AS/NZS 1754.6 In contrast, only the joint Australian/New Zealand standard is accepted in Australia, and the child restraint law specifies a minimum age for use of each restraint type (e.g. 6 months for a forward-facing restraint, 4 years for a booster seat).While acceptance of restraints from all over the world certified to multiple standards appears to offer more choice to New Zealand families, these potential benefits are more than outweighed by the complexity of choosing the ‘best' restraint for a child, because different standards use different selection criteria (weight, age, height, shoulder height).Particularly confusing is that a child who fits one type of restraint under one system may not fit a similar type of restraint designed to another standard. For example, a three year old child may be in the weight range for a US certified booster seat but not be tall enough to fit in an AZ/NZS 1754 certified one. This encourages premature graduation to a booster seat via choice of the US restraint, while evidence shows the child is much safer staying in their forward-facing restraint than in a booster seat at this age.A good example of how to make restraint selection easy for parents is the new shoulder height marker system used on restraints certified under the Australian/New Zealand standard since 2010. These labels are placed on the restraint indicating the minimum and maximum shoulder heights for a child to fit properly in that restraint.These labels make it clear at a glance when a child fits into a particular restraint, because their shoulders must be between the two labels on the restraint. It discourages premature graduation because if a child is too small for the next restraint category, their shoulders will be below the minimum height label. This is a much simpler and more reliable way of choosing a restraint 7 than relying on the parent knowing the child's weight or height (many parents either do not know or their estimates are wildly inaccurate), and gives better fit of the child in a restraint, and therefore better protection in a crash.Another major safety concern is the continuing approval of child safety harnesses (or "H-harnesses") for use by children under 7 in New Zealand (www.nzta.govt.nz/traffic/students-parents/child-restraints.html), as research has shown that they can be particularly dangerous in crashes, and that they offer no benefit over lap-sash seatbelts.8Indeed the latest Australian/New Zealand Standard restricts their use to lap only seatbelts together with a booster seat that can stop the harness pulling up in a crash, allowing a child to slide under it. Children under 7 should not use harnesses without a booster seat. The recently published Australian National Guidelines for Child Restraint Use,9 which were approved by Australia's National Health and Medical Council in 2013, recommend against their use.The other critical aspect of child passenger safety is using restraints correctly. Incorrect use of restraints also substantially increases injury risk, by up to 7 times.10 Child restraint checking and fitting schemes have been shown to significantly reduce misuse,11 and the recommendation that parents make use of these schemes by the New Zealand Paediatric Society is valuable.Newer restraint installation systems, such as LATCH and ISOFIX can also reduce incorrect use. However, this is another area where the acceptance of multiple restraint standards in New Zealand makes parents lives much more difficult and potentially increases the risk of injury for New Zealand children, because different standards have different ways of installing restraints and different requirements for securing the child in the restraint. For example, top tether straps that connect the top of a child restraint to the car are highly effective in reducing injury, but their use on US and European restraints varies with the type of restraint and the type of installation system, while the joint Australian/New Zealand standard requires them for all infant and forward facing restraints, and many booster seats.Parents therefore know that all restraints require top tethers, rather than having to remember which restraint needs one. This is reflected in the substantially lower rates of top tether misuse seen in Australia than in the USA (~20% vs ~60%12,13).The bottom line is that we need to have a simple, consistent system for child restraint selection and use so parents can easily know what is ‘best practice' and how to achieve it. This requires design of legislation that sets the societal norms for restraint use to be equal to best practice, while allowing for exceptions as required to make it practical. These laws need to be supported by targeted education and child restraint fitting advice services.