Background Premature graduation to an adult seatbelt is common and detrimental to optimal crash protection. While there is an existing tool (the 5-step test) to support a parent’s decision to graduate their child, its effectiveness is unknown. The aim of this study was to evaluate the 5-step test.

Method A randomised controlled design was used. Participants were parents of children aged 7–12 years. After exposure to information about the 5-step test or control material, participants assessed belt fit in three seating conditions and ‘thought aloud’ while making their assessment. Seating conditions provided a good, poor and partially good seatbelt fit based on the child’s anthropometry. Participants were also assessed on their knowledge of good seatbelt fit criteria.

Results Participants exposed to the 5-step test (n=18) had significantly improved their knowledge of the criteria required to achieve good seatbelt with, on average, 1.0 higher score in the 6-point assessment (95% CI 0.23 to 1.7, p=0.012) than those in the control group. There was also a greater percentage of participants in this group (44.4% intervention vs 27.8% control) who made accurate decisions about seatbelt fit, but this difference did not reach significance (OR 2.08, 95% CI 0.52 to 8.34).

Conclusion The results demonstrate that the 5-step test is effective in improving knowledge but are inconclusive about its effectiveness in promoting accurate decision-making. However, the proportion of participants making accurate decisions in the intervention group remained low. This suggests that parents may require greater assistance than what is currently provided.