Civil Engineering PE

Answer: C - The passing sight distance for a section of 60 mph 2-lane rural highway with a 1,740-ft vertical sag curve when a bridge passes over at 16.8 ft is 2,273 ft.

Solution: Use sag vertical curve length at undercrossing equation (US Customary units)

S = sight distance = L/2 + {[400 x (C - 5.75)] / A}

Where:
L = vertical sag length = 1740 ft
C = bridge height = 16.8 ft
A = % difference in grades = 3.15
5.75 = 0.5 x (object height + eye height)

S = (1740 / 2) + {[400 x (16.8 - 5.75)] / 3.15}

= 2,273 ft