This study has been carried out to investigate the effect of traffic load on the level of blood adrenaline hormone and its influences on the distance estimation and recognition accuracy among urban bus drivers. The level of blood adrenaline hormone has been regarded as stress index. Sixty-nine urban bus drivers were investigated on heavy- and low-traffic days. The precision of distance estimation and the recognition accuracy among this population were also evaluated in both situations. The level of adrenaline in drivers' blood on heavy-traffic days was more than low-traffic days. The means of recognition accuracy and distance estimation precision showed that the drivers' ability has decreased on high-traffic days as opposed to low-traffic days. The increase of the drivers' blood adrenaline on heavy-traffic days could make the drivers more stressed out, as their precision and judgment might be reduced.
Keywords: adrenaline; precision; stress; urban bus drives.