A ramp with one 12 ft wide lane is to be designed to provide access to the inter

Question

A ramp with one 12 ft wide lane is to be designed to provide access to the interstate A from the state route B. Figure 1 shows the layout of the interchange with center line of the merging and exiting lanes The two highways intersect each other at 90° and there is an obstruction from the corner of an old historical building (C) at the interchange as shown in the figure. The construction is to be performed without demolishing the historical building. Perform two alternative designs considering all aspects of the problem including driver satisfaction and cost. Different design options may include different superelevation radius or speed considerations. The maximum superelevation permitted is 600, the coefficient of side friction is 0.15 and the speed limit on the state route is 50 mph. For each design solution, provide the following (a) The radius and length of the curve, and the location of the center of the curve on DE (b) The speed limit sign to be posted on the ramp (c) The superelevation Show all steps with two distinct alternatives clearly identified. Interstate 5 A StaC180 ft te 180 ft storic Buildin ute Figure 1. Interchange layout

Explanation / Answer

With the allowable speed of 50 mph and Superelevation of 6%,

The Design radius of curve would be = (velocity ^ 2) / (Acceleration due to Gravity * (Superelevation + Coefficient of lateral Friction) ;

Hence, Radius calculated will be = 796 fts

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