Civil Engineering - Highway Engineering - Discussion


A district road with a bituminous pavement has a horizontal curve of 1000 m for a design speed of 75 km ph. The super-elevation is

[A]. 1 in 40
[B]. 1 in 50
[C]. 1 in 60
[D]. 1 in 70
[E]. none of these.

Answer: Option A


No answer description available for this question.

Yugananth P said: (Aug 26, 2013)  
e = V^2/225R.

= 75 * 75/(225*1000).

= 1/40 (or).

= 1 in 40.

Arnab Chanda said: (Mar 23, 2014)  
But it is not declared that 1000 m is the radius of the curve.

Muleta Totoba said: (Mar 24, 2014)  
Right it is not declared but the term curve seems something to be the given figure 1000 is the radius.

Surya said: (Aug 2, 2014)  
e = V^2/gR.
V = 75% of design speed.
V = 0.75*75.
v = V/3.2.

Jay Mishra said: (Aug 28, 2014)  
I think superelevation = v^2/127r.

Deepak Mittal said: (Sep 17, 2014)  
No it should not be v^2/127r. If the value of f then you can take the v^2/127r. Otherwise V^2/225R.

Biswa said: (Nov 17, 2014)  
e = (0.75v)^2/Rg.

v in m/s.

Ans: 1 in 40.

Reshma said: (Dec 3, 2014)  
We have to design for 75% speed means super elevation for mixed traffic.

e = (0.75V)^2/gR = V^2/225R.

Anitha said: (Dec 26, 2014)  
We have to design for 75% speed.

So, e = (0.75v)^2/g.r;

v = 75kmph = 75/3.6 = 20.833.

e = (0.75*20.833)^2/(9.81*1000) = 0.02488.

1/40 = 0.025.

Shankar Meghwar said: (Jan 24, 2015)  
R = V^2/225(e+fs).

Consider coefficient of friction as fs = 0.

Therefore R = V^2/225 e.
e = V^2/225 R.
= 75*75/(225*1000).
= 0.025.
= 1 in 40.

Manoj Kumawat said: (Feb 24, 2015)  
According IRC : The super-elevation is calculated for 75% of design speed.

So e = V^2/225R.

27-27 said: (Mar 14, 2015)  
Design speed is given use: e = (0.75v)^2/gR.

In a question if they are given only speed then use: e = v^2/gR.

Aditya said: (Jun 26, 2015)  
Guys can you please tell me the density of GSB, WMM, DBM and also BC?

Banoth Ramesh said: (Aug 3, 2015)  
ANS (A).

e = V^2/225R.
e = 0.025 = 1 in 40.

Ram Kumar said: (Oct 10, 2015)  
e = v^2/(127R) this formulas use.

And get the super elevation.

Pratik said: (Oct 13, 2015)  
Radius is not mentioned.

Mohamed Yaagob said: (Jan 30, 2016)  
F = 0 V = 0.75 V design speed.

E = (0.75 V)^2/(127 R).

Prashant said: (Feb 24, 2016)  
1000 m is length of curve here, not radius.

Ies Akp said: (Apr 1, 2016)  
1000 m is radius, it can't be length because there is no relation to provide length.

Osi said: (Jun 21, 2016)  
But we have studied it in the formula = v^2/126R. I am confusing which one is correct.

Miki said: (Jul 30, 2016)  
Both the formula is correct, the only difference is in e = v^2/127R, uses 75% of speed, and in e = V^2/225R, we are directly used.

Ravindra said: (Aug 21, 2016)  
The given answer is true, don't confuse it.

Jatav Shurjeet Singh said: (Sep 2, 2016)  
It is the right answer, it will use v^2/225r.

Jack said: (Sep 8, 2016)  
A District road having the mixed traffic condition so speed is reduced by 25%.

Super elevation e = V^2 / 225 R.
e = 75 * 75/225 * 1000
= 0.025.

so for 1m,
1/0.025 = 40.
=> 1 in 40.

Shailendra Kumar said: (Oct 9, 2016)  
I think the formula of superelevation e= v^2/225R.

So we put all values as given in the question e = 75 * 75/225 * 1000.
e = 1/40.

Kruti Nayak said: (Oct 17, 2016)  
v^2/225R is correct.
v^2/127R when f = 0.

Joel said: (Oct 17, 2016)  
The provided answer 1 in 40 is correct.

Happy said: (Dec 1, 2016)  
But, here v^2/225 is the highest unit of super-elevation.

Mukeah Senani said: (Dec 13, 2016)  
E = V^2/225R -> this method is Right.

Jayrajsinh said: (Dec 14, 2016)  
Practically super elevation e = v^2/225R.

So answer 1 in 40 is correct.

Sonu said: (Dec 19, 2016)  
If f is not given so we apply e = v^2/225R . The answer is 1 in 40.

Titan said: (Dec 21, 2016)  
Why is everyone assuming R=1000?

I think the curve length is 1000, not R. And the angle is not given.

Yohannis said: (Jan 12, 2017)  
The question stated that 75km/hr is design speed, thus simply we can calculate e=(75^2)/225R. b/c 'f' is not given.

There fore, 1:40 is the correct answer.
If 'f' were given, we use (e+f) = (75^2)/127R.

Danjah said: (Jan 14, 2017)  
here 1000 m is the length of curve, not radius.

Haylee Ethio said: (Feb 19, 2017)  

We Have,
V= 75Km/h
= 75^2/225(1000)
=1/40 is the Correct one.

Rehi said: (Feb 24, 2017)  
Actually, in the problem, it shows that horizontal curve is 1000m but in explanation, they take 1000m as a radius why don't they take it as length of the curve?

Sharad said: (Apr 2, 2017)  
Let's clear something out first,

e+f=v^2/127r (When V is in kmph) and
e+f=v^2/225r (When V is in mph)

For initial design, we assume mix traffic and hence the velocity reduces to 75% and f is taken as 0.

So, the equation will be e=(0.75v)^2/127r.
Now, the answer will be 0.0249 or 1 in 40.

Naren said: (Apr 3, 2017)  
Why we take 1000 as R why don't we take it as the length of the curve? Could anybody please explain me this?

Geetha said: (Apr 4, 2017)  
V^2/127R is the formula for super elevation.

We will use use this (V^2/225R )formula only mixed traffic condition is given.

Palash Mondal said: (Apr 8, 2017)  
The actual formula of super elevation is;

We know the super elevation is calculated for 75% of design speed.

E = (.75V)^2/GR.
V = Desing speed.
G = Gravity.
R = Radios.

E = (.75 * 20.83)^2/9.81 * 1000,
V = 75 * 1000/60 *60,
V = 20.83m,
E = .2488,
E = .25 approx,
E = 1/40 answer.

Babugouda said: (May 5, 2017)  

e = v2/gr when v is in m/s.
e = v2 /127r when v is in kmph.

Sameer Naik said: (Jun 28, 2017)  
Why used 75% in que not mention mixed traffic?

Rajesh Kumar Saini said: (Aug 19, 2017)  
1/40 is the right answer.

Harveer Singh said: (Aug 26, 2017)  
1 in 40 is the right answer.

V^2/125r ( f is not given).

Yamir said: (Aug 28, 2017)  
F is not gives that doesn't mean we will not use 127 Maximum times we use 127 for already designed roads.

Azanaw said: (Sep 13, 2017)  
Why 75% is taken for design speed?

Janardhan said: (Sep 16, 2017)  
e=V2/225R when V in KMPH,
e=v2/127R-f ,if f is given,
and v in m/s,other wise e=v2/127R if f is not given.

Himanshu Kumar said: (Sep 29, 2017)  
But there speed in kilometer and horigental curve in meter so how it is possible? Please explain.

Deven Negi said: (Oct 26, 2017)  
Radius are not mentioned.

Manish Chandel said: (Jan 4, 2018)  
e=v^2/225*R is correct.

Dj.Thakur said: (Jan 15, 2018)  
For design of superelevation on road:-

(1)- design superelevation for 75% of design speed. (Hence s.e. resists 75% of centrifugal force rest is balanced by road friction)

Haroon said: (Mar 4, 2018)  
e+f=v^2/gr, v in m/s.
e+f=v^2/127r, v in km/h.

For 75% of design speed f=0,as per irc.
e=(0.75v)^2/127r =v^2/225r.

Anmol said: (Jul 2, 2018)  
It's we have already given the design speed so we will use v2/127r.

Dev said: (Aug 15, 2018)  
Here it's v^2/127r.

Anwar Zaib said: (Sep 1, 2018)  
To determine super elevation we need only f- value, design speed and radius of the curve. So, if it is not mentioned then directly take the value with the unit of distance i.e meter.
the formula for mix traffic.

e + f = V^2/225R
f = 0 R=1000m and V =75kmph
e= 0.025 (1/40).

Surafel Belayneh said: (Sep 13, 2018)  
A District road having the mixed traffic condition so speed is reduced by 25%.

Super elevation e = V^2/225 R.
e = 75 * 75/225 * 1000.
= 0.025.

So for 1m,
1/0.025 = 40.
=> 1 in 40.

Yash said: (Nov 19, 2018)  
Already design speed is given, then why it converted again to design speed? Please tell me.

Sonam Phuntsho said: (Jan 6, 2019)  
What is the location of the road is on hilly area?

Mayur said: (Jan 24, 2019)  
Use e= (0.75v)^2/gr.

Singh Bushan Chib said: (Mar 6, 2019)  
It is right 1/40 by using the formula.

Rahul said: (Apr 19, 2019)  
In this question clearly mentioned design for the road not for any particular vehicle.

In the design of road assume friction is zero and 75% velocity ie formula of e is v^2/225R.

Tabaamith said: (May 12, 2019)  
Convert 75km/hr to m/ sec, which comes 20.85m/sec.
Take velocity as 75% of design speed.
Now, e= (0.75 * 20.85)^2/ 9.81X1000 = 0.024.
In ratio 1/1/0.024 = 1 in 40.

Kara Lala said: (May 20, 2019)  
GSB - Granular Sab Base.

WMM - Wet Mix Macadam.

Arjun said: (Sep 16, 2019)  
Design superelevation is always taken as 75% of the Design Speed hence it is e = v^2/225R.

Mohammed said: (Nov 6, 2019)  

You will find a clear explanation in IRC 38 codebook. However, I will try to briefly summarise it to you.

Basically superelevation is provided to counteract the centrifugal force experienced by a vehicle when it's negotiating a curve. Now counteracting the full centrifugal force developed for a given design speed would require us to provide superelevation of more than 7%. But IRC restricts the maximum value of e= 7%.

So in practice for mixed traffic, most vehicles travel at less than design speed (where we have both slow and fast-moving vehicles) so as a compromise since we can\'t provide the actual value we design superelevation to resist the full centrifugal force developed at 75% design speed.

Eg: If the design speed of a National Highway is 80kmph. We design the superelevation to fully resist the centrifugal force developed due to 75% of 80kmph = 60 kmph.

This method of giving superelevation will not be inconvenient to fast-moving vehicles but would be of aid to slow-moving vehicles.

Ramkishor Sahu said: (Dec 16, 2019)  
Superelevation is always.


But for the design of the superelevation we take,


So, Here velocity 75 kmph and horizontal curve 1000 meter given.

That means it is the radius of the horizontal curve.

Note:- Horizontal curve always given in the form of the radius.

Put these values to find the horizontal curve,

e = 75^2 / (225*1000).

e = 1/40.

Thank you.

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