DESIGNING HORIZONTAL CURVES FOR LOW-SPEED ENVIRONMENTS

This project was a pilot study to explore alternative criteria for the geometric design of low-speed urban horizontal curves. Low-speed was defined as 70 kilometers per hour (km/h), or 45 miles per hour (mph), or less. The researchers collected data and then developed alternative low-speed urban horizontal curve design paradigms. The study considered factors such as curve radius, pavement cross slope, vehicle speed within the curve, and vehicle speed in advance of the curve. The results were compared with the practices in the current American Association of State Highway and Transportation Officials A Policy on Geometric Design of Highways and Streets (Green Book). The data indicated that a driver's speed in advance of a curve can influence speed within the curve, and that a portion of drivers exceed the low-speed urban side friction factors in the 2001 Green Book. During the process of conducting the research, a number of observations were made which could be useful to those conducting related research in the future.