Highway Engineering please answer 1.2&1.3 l components making the stugping sight

Question

Highway Engineering
please answer 1.2&1.3

l components making the stugping sight distance 1 e stopping sight distance er the crest vertical curve stavan f G*-23% % G+44 1.3 Answer ITruelor (Fat nit comsiute ilel and raxide a comment on you ansner (mment Curve length 1500 sight distance for avoidance maneuver category "A" is similat to stoppung sigta distarvxe but with longer teaction time (b) A vertical curve connecting (c) The sag curve len two poitse grades is always-crest" is the distance and angle of prupection by vchicle head light during night time

Explanation / Answer

Let L > SSD Hence L = (N x S2)/(2H + 2h)2 N = algebric difference between grades S = Stopping sight difference H = height of man's eye = 1.2m h = Height of object = 0.15m Substitute in above equation we get L = (N x S2)/4.4 Given L = 1500 m N = 4.4-(-2.3) = 6.7 Solving 1500 x 4.4 = 6.7x S2 Stooping sight distance = S = 31.4m 1.3 1.False - Stopping sight distance is basically used when there is one distinct obstacle visible to driver's eye. Where as decision sight distance is used when there is large complexity and conflicts are maximum such as maneuvers As per AASHTO 2001,for decision sight distance, Avoidance maneuver A: Stop on rural road - t = 3.0s and eye height is 1.5and 600mm for object height. Whereas in stopping sight distance the reaction time is 2.5s and eye height and object height is 1.5m and 0.15m respectively. 2. Crest usually denotes the change of gradient from positive to negative like hills (parabolic).Hence joining two positive grades becomes a slope rather crest.So false 3. When you say sag curve it means it is a valley curve which changes from negative to positive. Usually for sag curve these criteria is taken into account a. The head light distance and ange b. Then drainage is important since it’s a valley curve and consideration of same is vital c. Comfort of driver, but in most cases it is comfortable at on half since there is natural gravitation force when downward, the consideration is majorly for the positive gradient of the curve. d. a rule-of-thumb for general appearance. Hence False

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