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# Transition (spiral) Curves

Posted in Highway Engineering |  Email This Post |

While taking a turn,the centifugal forces develop so a vehicle and its contents are immediately subjected to centrifugal forces. More is the speed of vehicle sharper is the curvature and thus the greater the influence on vehicles and drivers of the change from tangent to curve. When transition curves are not provided, drivers tend to create their own transition curves by moving laterally within their travel lane and sometimes the adjoining lane,which is risky not only for them but also for other road users.

Mathematically
The minimum length L, ft (m), of a spiral may be computed from

L=3.15V3/RC

where
V =vehicle velocity, mi/h (km/h)

R= radius, ft (m), of the circular curve to which the spiral is joined

C= rate of increase of radial acceleration

An empirical value indicative of the comfort and safety involved, C values often used for highways range from 1 to 3.

More Entries :
• Tapas Parui October 27, 2008 at 3:22 am

I want to know details of Transition Curve in highway (combined in circular)

• Debasish Biswas April 15, 2011 at 6:16 am

Dear Tapas,
Please go through IRC 38 & 73 and everything will be clear to you about Transition Curve

• Amir February 15, 2013 at 10:53 am

What’s IRC 38 & 73? How can I find IRC 38 & 73 on the net? (I searched but I have found nothing.)

• soumen April 24, 2009 at 3:27 am

I wanna get a detailed book in transportation engg. where geometric design of highway is available.

• zinash damtew April 29, 2009 at 1:42 pm

I want to know details description of Transition Curve,circular curve,horizontal curve.. in highway.

• Zohouri Radwan July 23, 2009 at 7:01 am

How can I select or assume the appropriate C value
whithout recommended schedule or equation depends on
speed changeable .so could I the required information to
determine or select the rate of increase of radial acceleration .
Full thanks

• concrete road September 30, 2009 at 10:13 am

Greetings to you,i’d like to compute or give me the formulas of concrete road with all details from foundation to the end.
thank you a lot

• Basim Sha P.K November 9, 2009 at 12:14 pm

I want to know the calculations and formulas involving in a flexible pavement road from start to end …….regards

• Raju December 22, 2009 at 2:54 am

Sir ,
According to IRC,
1)Allowable rate of change of centrifugal acceleration (I),
For speed less than 32kmph,I-0.76
,, ,, exceeding 96kmph I-0.46
And for speed in the range 32-96 kmph I-73/(V+96)
2)I-80/(75+V) and value lies between 0.5 to 0.8.
Sir in two different books i saw two different cases.Which one is true? and what is the
Difference?

• Pazarac March 17, 2010 at 6:07 pm

I have master degree in civile engenering and I would like to work in usa, where can I inform myselve about that. Sorry for my bad eng.
and sorry for interopting but for all roads everything is how u calculate curve (Bs+radius R) and if u combine that no problem in any curve on the road.
U are talking about some simple things there are 10 ways for every problem ( on u is to deside which is the best for u)
My best regards for all of u

• Mohemedi Masele February 11, 2011 at 12:10 pm

In which cases is it advisiable to use a transition curve, but not a circular curve?

• Lazarus Mapinyi August 31, 2011 at 12:05 pm

I’m doing land surveying, would like to much about transition curves. so my you help with somemore notes

• Lalit Sharma December 5, 2011 at 1:44 am

sir as per irc codal provision min 150 m curve length is to be provided at deviation angle more than 5 d this 150 m length includes spiral curve length with curve length or we can make cicular curve length zero