Samenvatting
A 56 week census of inspection records was conducted in a New Zealand borough where the Ministry of Transport had a monopoly on vehicle testing. By matching inspection records on registration numbers, it was possible to compute time and distance between consecutive inspections. Two variables, vehicle age and distance driven between inspections, were seen to have a strong bearing on failure rates. The exposure- adjusted defect rate was seen to be remarkably linear, increasing from newest to oldest.