This study examines the effectiveness of Iowa's Driver Improvement Program (DIP) by gender and age, measured as the reduction in the number of driver convictions and crashes subsequent to the DIP. The analysis involved a random sample of 9,055 drivers who had been directed to attend DIP and corresponding data on driver convictions, crashes, and driver education training history that were provided by the Iowa Motor Vehicle Division. The sample was divided into two groups based on gender (female and male), and three groups based on age (30 years old or younger, 31 to 40 years old, and older than 40 years old). In each specific group, the sample was then divided into two groups based on the DIP outcome, satisfactory or unsatisfactory completion. The evaluation period considered was one year after the DIP date (probation period) for each driver in the random sample.

The evaluation of Iowa's DIP showed that there is evidence of effectiveness in terms of reducing driver convictions subsequent to attending the DIP. Among the 6,790 (75%) drivers who completed the course satisfactorily, 73% of drivers had no actions and 93% were not involved in a crash during the probation period. Turning to the differences by age and gender, male drivers and young drivers (30 years old or younger) incurred more convictions, while older drivers (40 years old or older) had fewer crashes in both the satisfactory and unsatisfactory groups. Drivers in the satisfactory groups had lower conviction rates but more crashes than those in the unsatisfactory group. Econometric modeling estimation results showed that, regardless of the DIP outcome, the likelihood of a conviction and frequency of subsequent convictions depends on other factors such as age, driver history, and DIP location, and interaction effects among these factors. The association rules show that DIP is not associated with a reduction in the likelihood of the occurrence of one crash after DIP. This is consistent with previous studies in which the effectiveness of DIP in reducing subsequent crashes could not be established.

Low-cost, early intervention measures are suggested to enhance the effectiveness of Iowa's DIP. These measures include advisory and warning letters (customized based on the driver's age) sent within the first year after the DIP date and soon after the end of the probation period, as well as a closer examination of DIP instruction across the 17 community colleges that host the program. Given the large number of suspended drivers who continued to drive, consideration should also be given to measures to reduce driving while suspended offenses. Other states also can benefit from this study and results.