Abstract
In order to explore function of curve design, road information and driving conditions (season, and time of day), this study investigates driver's judgment on curve sharpness and driving behavior. The field study with an experimental group of 105 drivers has been conducted at 16 curves on a mountain highway, with employing 3 types of road information; non-treatment (actual roadway setting), advance curve-warning sign placed on the roadway, and roadway signing combined with curve-guidance through an in-car navigation system. The study then finds that information provision has a positive effect on driver's judgment on pre-curve sharpness under any road conditions, especially when the curve radiuses are less than 100 meters. On the other hand, however, several negative effects are found on driving performance of summer-daytime, particularly with roadway signing combined with curve-guidance through the in-car navigation system
