This study explores the effects of truck type and driver age on mental workload and driving performance among professional truck drivers in Indonesia. Thirty drivers—operating wing box trucks, tanker trucks, and dump trucks—participated in a simulated motorcycle detection task while their heart rate variability (HRV) was continuously monitored. Performance metrics included response time, misses, and errors, while mental workload was assessed using HRV parameters such as LF power, HF power, and RMSSD. MANOVA results revealed significant differences across truck types, with dump truck drivers showing slower response times, more errors, and lower HRV, indicating higher cognitive and physiological workload. Age also played a role: drivers aged 40 and above exhibited greater performance decline and reduced HRV indices, suggesting diminished cognitive flexibility and stress resilience. Correlation analysis confirmed that longer response times and increased errors were associated with lower RMSSD, reinforcing the relationship between elevated workload and impaired performance. These findings highlight the importance of truck-type-specific and age-adaptive safety interventions, including targeted training, ergonomic design improvements, and physiological monitoring systems. The study contributes to the development of human-centered strategies for enhancing driver well-being and improving road safety in freight transport.