A two-lane minor road, with +2% approach grade, in the North-South direction int
ID: 1710796 • Letter: A
Question
A two-lane minor road, with +2% approach grade, in the North-South direction intersects a two-lane major road in the East-west direction that has a speed limit of 40mph, a +5% approach grade, forming a 4-leg intersection. A building is located at the South-East corner of the intersection as shown in the figure below. If the intersection has no control and the vehicle on the major road will adjust speed, determine the maximum speed on the local road in order to allow a driver on the minor road to: (Assume a perception-reaction time of 2.0 seconds and a coefficient of friction of 0.35) (a) Adjust speed. (8%)Explanation / Answer
The above mentioned can be found by calculating the stopping sight distance at the minor road.
Formula to be used for stopping sight distance = vt + v2/2gf
where v = design speed
t = perception time
g = gravitational constant
f = frictional co-efficient
The stopping sight distance can be calculated for the vehicle in the major road & with the stopping sight distance, using the uniform distance of stoppnig for the minor road, maximum speed for the minor road can be calculated.
Stopping sight distance for the major road = 76.60m
using this value, the speed for the minor road with 2% approach grade can be calculated
Speed for the minor road = 34.1mph
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