Civil Engineering Tools
BeamTrussMohr's CircleUnit ConversionsCentroidDeflectionBucklingConcreteRebarFE Prep

Stopping Sight Distance on a Level Road

Mediumstopping sight distancebraking
A vehicle travels at 20 m/s on a level road. Perception-reaction time is 2.5 s and constant braking deceleration is 3 m/s2. What is the approximate stopping sight distance?
  1. A50 m
  2. B67 m
  3. C100 m
  4. D117 m
Show solution

Answer: D. 117 m

Equation: stopping sight distance SSD = v·t + v²/(2a), the perception–reaction distance plus the braking distance. Values: v = 20 m/s is the initial speed. t = 2.5 s is the perception–reaction time, during which the car keeps its full speed. a = 3 m/s² is the braking deceleration. Step 1: perception–reaction distance, v·t = 20 × 2.5 = 50 m. Step 2: braking distance, v²/(2a) = 20²/(2 × 3) = 400/6 = 66.7 m. Step 3: SSD = 50 + 66.7 = 116.7 ≈ 117 m. 50 m and 67 m are each only one of the two segments.
Practice this deckUntimed, one problem at a time, with your progress saved.

Related problems

Keep studying