To improve the safety of traffic in road tunnels, the effects of adaptation on peripheral visual performance were studied by measuring subjects’ reaction times and missed target rates. The process of driving through an illuminated road tunnel was simulated in the laboratory by gradually decreasing the luminance of the visual environment. The tests showed that the gradual luminance changes resulted in transient blindness and decreased visual performance. The subjects’ acuity and alertness were better for bluish targets than for reddish targets and better for whitish targets than for greenish targets in the tunnel transition and interior zones. The S/P ratio and mesopic luminance in the transition and interior zones, respectively, should be considered when selecting road tunnel luminaires.