Question

9. (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).10 0

Fig: 1

Fig: 2

Fig: 3

Fig: 4

Fig: 5

Fig: 6

Fig: 7