Tiêu đề MSTE 39 Solutions.pdf ✅

39 Transportation Engineering: Sight Distance Solutions SITUATION 1. A driver traveling at 50 mph is 80 m from a wall ahead. If the driver applies the brake immediately at a brake reaction time of 2 seconds and begins slowing the vehicle at 10 m/s 2 . ▣ 1. Find the distance from the stopping point to the wall. [SOLUTION] Reaction distance 50 mph × 1.609344 km 1 mile × 1000 m 1 km × 1 hr 3600 s = 22.352 m s dr = (22.352 m s ) (2 s) = 44.704 m Stopping distance ds = v 2 2a ds = (22.352 m s ) 2 2 (10 m s 2 ) = 24.9805952 m Distance from stopping point to the wall x = 80 − (44.704 m + 24.9805952 m) x = 10.315 m ▣ 2. Determine the braking time or time during deceleration. [SOLUTION] v = v0 + at 0 m s = 22.352 m s + (−10 m s 2 ) t t = 2.2352 s ▣ 3. Assume that the brake efficiency of the vehicle is 70%, find the average skid resistance of the pavement. [SOLUTION] eff = v 2 2gf

Using the comfort criterion, L = AV 2 395 L = (0.5 − (−1))(110) 2 395 L = 45.95 ≈ 60 m ▣ 6. The clearance to an obstruction is 9 m and the desirable sight distance when rounding a horizontal curve is 180 m. Determine the minimum radius of the horizontal curve. [SOLUTION] Assume that S < L M = S 2 8R 9 m = (180 m) 2 8R R = 450 m