In conditionally automated vehicles (CAVs), takeover requests (ToRs) must re-engage drivers quickly and effectively. This study examines how the type of ToR explanation (action-only, precursor-only, hazard-only, precursor+hazard) and hazard type (behavioral vs. environmental) jointly affect driver’s situation awareness, situational trust, and cognitive workload. In a driving simulator experiment using a 4×2 within-subjects design, 12 participants experienced all conditions while engaged in non-driving tasks. The findings suggest that while more informative explanations significantly improved situational awareness, trust, and satisfaction, they also imposed a greater cognitive workload. Behavioral hazards consistently led to better outcomes, whereas environmental hazards were more sensitive to explanation quality. Significant interaction effects emerged across most measures. This study underscores the importance of adaptive, context-aware ToR interfaces that adjust information to both the driving environment and cognitive demands. Balancing informativeness with mental workload is key to enhancing safety and trust in automated driving systems.