Age, gender and the effectiveness of high-threat letters: An analysis of Oregon's driver improvement advisory letters

The Oregon Driver Improvement Program monitors driver records and takes corrective action at each of four levels. The advisory letter is the first level. An automated quality control system randomly withholds actions from five percent of drivers, producing a control group. Records of 27,026 advisory letter recipients and 1453 control subjects were analyzed. Of the 27,026 letter recipients, 13,623 received a randomly assigned, experimental soft-sell letter and the rest a standard letter. Records were monitored for 24 subsequent months. Overall, those receiving either advisory letter had fewer traffic accidents than the control group, and the standard letter is significantly more effective than the soft-sell letter. However, there are several apparent differences in effectiveness by age and by gender. The standard letter is clearly more effective for younger drivers but the soft-sell letter appears to be most effective for drivers over age 45. Considering gender, both letters reduce collisions but the standard letter is more effective for men. For women, the standard letter is more effective than the soft-sell letter, but not more effective than no letter. In fact, accident-free survival for women receiving no letter was nominally but not significantly higher than for women receiving either letter. There are no significant differences in moving violations. However, with regard to major traffic violations, those receiving letters had significantly higher violation free survival, although there were also notable differences in effectiveness, by age.