The objective of this paper is to summarize the recent research on effects of carbon monoxide on driving performance conducted by the Driving Research Laboratories at The Ohio State University. The major research question was to determine the effects of carboxyhemoglobin levels on nighttime driving performance of young drivers and in comparison with the performance of aged drivers. Experiments in the real highway environment were conducted to seek answers to the above research question. The driving test battery consisted of freeway driving, reading highway signs, car following, driving with voluntary occlusion (this task designed to measure the spare visual capacity of drivers), curve negotiation and estimation of time and velocity while driving. The test subjects drove an instrumented vehicle capable of recording, on a video tape, the road scene, the point of driver's eye fixation, elapsed time, and distance traversed. The vehicle was also equipped with an FM recording system which recorded steering wheel movements, vehicle velocity, lateral acceleration and driver's heart rate (EKG).

In the experiment five young healthy nonsmokers and five healthy aged (60 to 65) nonsmokers participated. Each subject was treated with 0 and 12 percent nominal COHb levels. In this research the subjects acted as their controls and the experiments were carried out "double blind."

The results from the research included 1) 12 percent COHb level significantly affected the nighttime visual search behavior of both the young and aged subjects but in a significantly different manner. The trend towards decreased visual activity that was observed during daytime driving performance of the earlier experiment was confirmed for nighttime performance for young subjects. 2) Under the influence of 12 percent COHb level the aged subjects demonstrated less peripheral sensitivity. 3) Twelve percent COHb significantly increased the mean heart rate of the young subjects whereas no change was observed for the aged subjects.

In general CO effects on the road are much less than those found inthe laboratory. The results indicate that CO effects are first manifested in the visual system before driver control or vehicle performance measures are affected.