An existing equal-tangent sag vertical curve is designed for 60 mi/h. The initial grade is -3% and the elevation of the PVT is 754 ft. The PVC of the curve is at station 134 + 16 and the PVI is at 137 + 32. An overpass is being constructed directly above the PVI.
The highway is for cars only (AASHTO minimum and recommended structure clearances do not apply) and the overpass design assumes the driver's eye height is set conservatively to 5 ft.
What is the lowest possible elevation of the bottom of the overpass structure to ensure sufficient stopping sight distance at 60 mi/h?