Do restricted driver's licenses lower crash risk among older drivers? A survival analysis of insurance data from British Columbia.

PURPOSE Faced with an aging driving population, interest is increasing in the use of restricted licenses or "graduated delicensing" for older drivers to allow them to safely retain a driver's license. The primary purpose of this study was to determine whether restricted licenses are successful at mitigating number of crashes per year and whether they can extend the period of crash-free driving for aging adults. DESIGN AND METHODS Using a cohort study design, licensing and insurance claims crash records of all drivers aged 66 years and older in British Columbia were examined for the years 1999-2006. Nonparametric and Cox proportional hazards survival analyses were used to compare restricted vs. unrestricted drivers and to estimate crash risks. RESULTS The risk of causing a crash for restricted drivers was 89% (or 11% lower risk) compared with unrestricted drivers after controlling forage and gender.[corrected]. The most common restriction was a combination of daylight driving only plus a speed maximum of 80 km/hr. Restricted drivers retained a driver's license for a longer period of time than unrestricted drivers and continued to drive crash free longer than unrestricted drivers. There was no difference in severity of collisions, and results suggest a high level of compliance with daylight-only restrictions. IMPLICATIONS These findings suggest that driving restrictions may be effective for prolonging the crash-free driving of some aging drivers, thus supporting their continued independence and delaying institutionalization. Further studies are needed to determine which drivers are most likely to benefit from restricted licenses.