Driving behavior shapes PHEV brake energy and brake wear particle emissions

• Braking behavior compared for ACC, aggressive, normal and 9 driving cycles. • Energy regen efficiency: normal > ACC > aggressive, traffic impact negligible. • RBS power-related constraints cause >90 % friction energy in aggressive driving. • Braking energy: behavioral impact significant on level terrain. • Driving behavior and pad material can double brake-wear PM 10 emission factors. Driving behavior strongly influences both energy efficiency and non-exhaust emissions of plug-in hybrid electric vehicles (PHEVs), yet quantitative evidence comparing adaptive cruise control (ACC) and human braking is scarce. We instrumented a PHEV on mountainous Chongqing roads and extracted >3000 braking events classified as normal, aggressive, or ACC across peak/off-peak traffic and benchmarked against nine standard cycles. Regenerative efficiency ranked normal 64 % > ACC 58 % > aggressive 53 %. Over 90 % of aggressive-mode friction energy occurred beyond the power limit of regenerative braking system (RBS); increasing RBS deceleration/power limits could regenerate 12–18 % additional braking energy. Estimated brake-wear PM 10 under aggressive driving was 2–4 times normal and often exceeded MOVES3/COPERT emission factors, indicating that inventory models underpredict where hard braking dominates. Behavior-energy-emission profiling suggests three levers: behavior-aware ACC tuning, higher-performance RBS hardware, and emission factors calibrated to local traffic and driving heterogeneity.