Question

EXIT 211 A A 2,125 ft equal tangent vertical curve joins a +2.2% grade to-3.6% grade. The PVI of the vertical curve is station 55+21 at elevation 150 ft. To meet MUTCD standards for advance guidance, an overhead sign structure must be placed at station 55+85. The bottom of the sign will be 18 ft above the roadway surface (more than the recommended 16.5 feet to accommodate larger trucks that use the roadway). WEST 56 Utopia Botlom of sign 18 feet a) What will be the elevation of the bottom of the overhead sign and the PVC and PVT elevations Roaway Surtece and stations? b) Is the sign a concern for SSD? Why or why not.

Answer 1

Ans a) Station at overhead sign = 55 + 85 ft

Height of bottom of sign from road =18 ft

Elevation of bottom of sign = (55+85) + (0+18)

= 55 +103

Also, we know,

PVI - PVC = L/2

PVC = PVI - L/2

= (55+21) - (2125/2)

= 44 + 58.5

PVT - PVI = L/2

PVT = L/2 + PVI

= (2125/2) + (55+21)

= 65 + 83.5

Now, PVI elevation = PVC elevation + (0.022 x 2125/2)

150 = PVC elevation + 23.375

PVC elevation = 126.625 ft

PVT elevation = PVI elevation + (0.022 x 2125/2)

PVT elevation = 150 + 23.375

= 173.35 ft

Ans b) Y = A (L/2)² / 200 L

A = change in grade = 5.8

L = 2125 ft

Y = 15.40 ft

Offset required is 15.4 ft < 18ft , so SSD is not a concern