(Solved): 3. The figure below shows the centrelines and pavement edges of a two-lane highway. There is an ex ...

3. The figure below shows the centrelines and pavement edges of a two-lane highway. There is an existing building at a distance "D" from the Point of Intersection (PI). A horizontal curve is used to connect the two centrelines. The curve has a superelevation rate of 4%. [20 marks] 3 15m .... P.I. D 30° Building C.L. 3.75m 3.75m i) Find the minimum distance "D" if design speed on this curve is 80 km/h? ii) Find the minimum spiral length required for this curve. iii) If this horizontal curve coincides with a vertical curve, which is designed to the minimum required length connecting a 3.0% and a -3.0 % grade. Check if the vertical curve can be entirely located within the horizontal curve. Explain how to phase the two types of curves in highway geometry design.