This study examined the influence of the comprehensibility of installation instructions for children's car seats on whether they were correctly installed. It also worked with parents to design new, more comprehensive installation instructions and evaluated the impact of these modified instructions. Nearly half of Australian parents using restraints are using them incorrectly which increases the risk of serious injury to children by up to three times. The study found that although 90 per cent of participating parents reported that they had read the instructions supplied with the restraints, high rates of incorrect use continued. There was a critical relationship between comprehension of instructional materials and errors in use, suggesting that the current instructional materials may not be effective in communicating how to use restraints correctly. The study found that working with parents to improve child restraint instructional materials resulted in 27 per cent more people attaining correct use, and comprehension of the instructions was 42 per cent higher.