Civil Engineering PE

Answer: B - The stopping sight distance (SSD) for a speed of 70 mph on a flat grade roadway is most nearly 492.4 feet.

Solution: Use the SSD equation for flat grade (US Customary units)

d = 1.47Vt + 1.075 V²/a

Where, t = 2.5 seconds

a = 11.2 feet/second²

V = 55 mph

d = 1.47 (55) (2.5) + 1.075 (55)²/ (11.2)

= 202.1 + 290.3

= 492.4 feet