Civil Engineering - Highway Engineering - Discussion

23. 

The absolute minimum sight distance required for stopping a vehicle moving with a speed of 80 km ph, is

[A]. 120 m
[B]. 200 m
[C]. 640 m
[D]. none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Dinesh said: (Jun 12, 2014)  
SSD = lag distance+braking distance.

= v.t + v^2/2gf.

= 22.22*2.5 + (22.2)^2/(2*9.81*0.35).

= 126.5 (near to 120) So answer is (a)120m.

Where v is in m/s and t = reaction time(2.5sec acc. to IRC).

f is longitudinal coefficient of friction.

Sarang Mote said: (Sep 26, 2016)  
What is the lag distance?

Jitendra Singh said: (Oct 16, 2016)  
Lag distance = vt.
V = m/ s.
T = sec.

Salman Mohammed said: (Nov 19, 2016)  
SSD = 0.27vt + v.v/254(f +-g/100).

Where t = 2.5.
f = b/n 0.43 and 0.4 interpolate.

So to answer the question in meter we must use this equation.

Navi said: (Jan 23, 2017)  
Actually its from the direct values given in the books (for 20kmph = 20).
So as (25=25) (30=30) (40=45) (50=60) (60=80) (80=120) & (100=180).

Ankur said: (Feb 6, 2017)  
How to predict the value of f in such cases?

Asita said: (Feb 17, 2017)  
Yes, right @Navi.

Ankur said: (Jul 1, 2017)  
We can predict because we have to calculate min SSD if take f= .15 we get more value but if we take f= .35 we get min value so we take f=.35.

Pakkirappa said: (Sep 16, 2017)  
V is given in kmph convert to m
I.e 1000/60*60=0.278
Ssd=vt+{v2/2gf}
Where t is time required for understanding the situation this is a constant value.
Ssd=0.27*80*2.5+{(0.27*80)^2/(2*9.81*0.35)}
Ssd=121.6m.

Shubham said: (Aug 11, 2018)  
Right @Navi.

Dinesh said: (Jul 21, 2019)  
0.28 * V.t + 0.01V^2/brake efficiency.
V = 80
t = 2.5
And We get exact ans 120.

Lucky Kumar said: (Mar 12, 2020)  
SSD = 0.278Vt+V^2/254(f+S%).
= 0.278*80*2.5+80*80/254(.35).
= 127.6 mtr.

Cofficent of friction (f) = 0.35.

Mayu said: (May 6, 2020)  
Longitudinal friction --------- 0.35 - 0.4.
Lateral friction --------------- 0.15.

Dipunku said: (Aug 28, 2020)  
The correct answer is 127.6m.

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