Question

Transportation Engineering

(25 points) As a junior roadway engineer, you have been asked to contribute to the design of a section of roadway that runs through a national park. An endangered deer population has been identified in the area and a wildlife underpass under a vertical curve has been proposed, as shown in the figure below. An existing underpass is perpendicular to the roadway at station 20+91.00 (not necessarily under the center of the curve). The top of the underpass is at elevation 407.50 ft. Studies by the ecologists and highway engineers recommend an 8-ft clearance between the roadway and the underpass to make the wildlife underpass usable to the deer population. According to the initial road design, the PVI is located at station 19+00.00 with elevation 420.50 ft. The design speed of the curve is 55 mph, G1 is +3.0%, and G2 is -3.0%.

a. Calculate the minimum length of this curve (L);

b. Determine if the clearance between the vertical curve and the underpass is adequate;

c. If the clearance is not adequate, what modifications to the curve design can be made to increase the clearance (assuming no modifications to the underpass and road grades are non-changeable)? Discuss possible ramifications of making this modification. (Hint: No need to do any calculations. Explain the relationship between curve length, design speed and stopping sight distance).

Station: 19+00.00 Elevation: 420.50 ft Clearance PVC PVT Underpass +3% -3% Top of the underpass Station: 20+91.00 Elevation: 407.50 ft

Answer 1

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