PE Civil Engineering Exam Prep

Answer: C - The passing sight distance for a section of 60 mph 2-lane rural highway with a 1,740-ft vertical sag curve where 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 = sigh distance = L/2 + [400(C-5.75)]/A

Where:

L = vertical sag length = 1740 ft

C = bridge height = 16.8 ft

A = % difference in grades = 3.15

And 5.75 = 0.5(object height + eye height)

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

= 2,273 ft