FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.A. Geometric Design. (continued)Example: A 20 km/h maximum differential in design speed is allowed between adjacent curves andbetween a curve and a long tangent. For a maximum radius curve with a 50 km/h design speed, flattercurves on either side could be superelevated for a 60 km/h design speed. A curve at the end of a longtangent with an expected operating speed of 100 km/h would be superelevated for a 80 km/h design speed.Tangents over 120 meters in length are considered long tangents.Table 9-3 is an example of how to record design speeds for a project.The following is a list of the sample design data entered into the table.Given:Basic design speed = 60 km/h.e max = 8%Road alignment =190 m tangent, 600 m radius curve right,98 m tangent, 300 m radius curve left,84 m tangent, 200 m radius curve right,73 m tangent, 150 m radius curve left,80 m tangent, 300 m radius curve right,93 m tangent, 900 m radius curve left,97 m tangent.9 - 22