| Suzuki et al. investigated the qualitative relationships between cues and assessment of curve sharpness in daytime and at night. They found that traffic control devices significantly affect the pre-judgment score but that these alone cannot provide complete information on the curve alignment. It should be considered how to inform the driver of the curve depth between back and forward tangents. However、 current warning curve sign do not provide curve depth information accurately. The driver can only estimate the sharpness subjectively using other traffic control devices、 road scene、 experiences on the route and so on. We propose a new device to provide curve depth information between back and forward tangents. The effects of information on a driver’s judgment of curve sharpness were investigated by the field experiments. Sixteen curve sections were picked up for sharpness assessment. 80 subjects estimated the sharpness subjectively in the daytime and at night. Three kinds of information were provided to inform curve depth accurately; paper map、 route map of the car navigation system and new warning curve signs. The bent arrow of the new curve warning signs roughly indicates curve depth. Each subject performed one run on the test section in daytime or at night. The subjects were required to judge the sharpness of each curve before and after the curve. The subjects were instructed to call their judgment of curve sharpness on the tangent section before the target curve. The experimenter gave the following explanation of the judgment criteria for curve sharpness: "’Sharp’ means that you are required to slow down before entering the target curve. ’Medium’ means that you are required to brake slightly before entering the target curve. ’Gentle’ means that you can run through the target curve safely without slowing down." The subjects evaluated their pre-judgment as soon as possible before the target curve. "Underestimation" means that the passed curve was sharper than predicted. The subject might be required to slow down in order to run through the target curve safety. "Accurate estimation" means that the passed curve was about as sharp as predicted. "Overestimation" means that the passed curve was gentler than predicted. After finishing the run、 each subject was asked several questions concerning the judgment of the curve. Scatter plots of pre-judgment scores vs. post-judgment scores are used to analyze the effects of information on sharpness judgment. As a result、 the adequate information indicated a positive effect on sharpness estimation. Almost information indicated positive effect on judgment of curve depth. The route map of the car navigation system represented the largest positive effect on sharpness estimation. In addition、 sharpness judgment at the left curve was more sensitive than that at the right curve. It should be noted that post-judgment score did not varied widely by pre-judgment scores. |
