For this exercise, you are to design a single-lane interchange ramp (so R = Rv) to connect two highways that intersect at a right angle as shown below (and as described in Example 3.18 on page 87). As in this example, the north-south highway is the existing highway and is at a constant grade at elevation 565.5 ft. The east-west highway new construction and is to be designed at a constant grade above the north-south highway with a bridge structure depth of 6ft to the roadway surface (you can determine the elevation of the east-west roadway using desirable AASHTO recommendations). The ramp designed in Example 3.18 is for eastbound traffic going south. Using the same roads (elevations etc.), design a clover-leaf ramp for eastbound traffic going north. The ramp is to consist of a horizontal curve starting on the east-west highway with a PC starting at station 49+60. For this ramp, a 12 percent superelevation is to be used with a 30mi/h design speed. Determine:
the length of the ramp, the minimum Ms for the curve sight distance, a vertical alignment to connect the two highways that starts at the PC and the ends at the PT of the horizontal curve, stations and elevations of the PVC's, PVI's, PVT's, PC and PT. Include a sketch of the plan (horizontal geometry) and a profile (vertical geometry), with appropriate annotations and dimensions.
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