A Driving Simulator Study on the Influence of Chevron Alignment Signs on Drivers’ Speed Choices on Horizontal Curves

摘要

The Chevron Alignment sign in China is a vertical rectangle with a white arrow and border on a blue background, which is different from the Chevrons described in the Manual on Uniform Traffic Control Devices in the U.S. To develop a practicable and clear guideline for implementing Chevron Alignment signs on China’s highways, it is first necessary to understand the effect of Chevrons on driving behavior in different roadway geometries. Using a driving simulator, this study tests the effect of China’s Chevrons on drivers’ speed on two-lane rural highways at horizontal curves with different roadway geometries. The results showed the significant effect of Chevrons on actual average speed. The function of Chevrons on speed reduction was not significantly affected by curve radius but was statistically affected by curve direction. The speed reduction caused by Chevrons was also significant at the approach of curve, middle of curve and point of tangent. We also found the 85th percentile speed was markedly lower when Chevrons were present. Chevrons did not significantly affect drivers’ perceived safe speed. Their presence did prompt drivers to perceive a higher safe speed for sharp curves, as compared with the absence of Chevrons. Hence, regardless of the curve radius, Chevrons at horizontal curves provide advance warning and speed control for traffic on the nearside of Chevrons. Besides, it appears that Chevrons can be used as a supplement to speed limit signs in preventing excessive speed on horizontal curves and therefore might contribute to a reduction in run-off-road crashes. Moreover, China’s Chevrons might also serve to provide an improved sense of safety while driving in sharp curves.