Age 70 as a threshold for vulnerable road user case fatality: A population-based study of older drivers in Taiwan

Age-based licensing renewal policies are implemented in aging societies to protect vulnerable road users (VRUs), yet the rationale for selecting age thresholds remains uncertain. This study examined whether age 70 represents a threshold for VRU case fatality among crash-involved older drivers and whether license status modifies this association. This population-based cross-sectional study analyzed Taiwanese police-reported crash data from 2011 to 2024 involving nonprofessional car drivers aged ≥ 50 years and VRUs. Driver age was modeled categorically and continuously using restricted cubic splines (RCSs). License status was examined as an exploratory effect modifier. A prespecified primary linear-spline analysis directly tested for a change in slope at age 70, while supporting RCS analyses evaluated overall nonlinearity. Multivariable logistic regression with cluster-robust standard errors estimated adjusted odds ratios (AORs) and 95% confidence intervals (CIs). Among 602,782 crash-involved VRUs, 2,789 sustained fatal injuries (0.46%). The prespecified analysis did not detect a change in slope at age 70 (change-in-slope AOR per year, 1.001; 95% CI, 0.977-1.025; P = 0.95), and the selected 3-knot RCS specification provided no evidence of overall nonlinearity (P = 0.24). Compared with drivers aged 50-64 years, odds of VRU case fatality were higher among drivers aged 65-69 years (AOR 1.15; 95% CI, 1.03-1.28) and ≥ 70 years (AOR 1.14; 95% CI, 1.01-1.29). However, among drivers aged 65-99 years, age ≥ 70 years was not independently associated with VRU case fatality (AOR 1.08; 95% CI, 0.93-1.25; P = 0.32). Unlicensed driving was associated with higher odds of VRU case fatality (AOR, 1.92; 95% CI, 1.62-2.28). Overall, the prespecified analysis did not detect a change in slope at age 70, while the association with unlicensed driving highlights a potentially important correlate of VRU case fatality among crash-involved older drivers.