Driving with only one headlamp working can reduce the visibility of reflective signs and devices at night, especially if the headlamp is misaligned. A computer model was used to analyze how different headlamp configurations and misaimed headlamps affect the detection distances of reflective targets on highways. The results suggest that it is crucial for headlamp systems to be reliable and long-lasting, for drivers to promptly replace malfunctioning headlamps, and for reflective materials on signs to be brighter to compensate for reduced visibility when driving with only one headlamp.