Civil Engineering - Highway Engineering - Discussion

To find the absolute minimum radius of a horizontal curve, we use the standard highway engineering formula:

R = V2127(e+f)R = 127(e+f)V2.
R = V2127(e+f)R = 127(e+f)V2.

Where:

RR = radius (in meters).
VV = design speed (km/h).
ee = superelevation (maximum, usually 0.07 or 7%).
ff = lateral friction (maximum, usually 0.15).

Given:

V = 60 km/h.
e = 0.07e = 0.07,
f = 0.15f = 0.15.

Calculation: R = 602127(0.07 + 0.15)R = 127(0.07+0.15)602​R.
= 3600127 × 0.22R.
= 127 × 0.223600​R.
= 360027.94.
≈ 128.8 mR.
= 27.943600​ ≈ 128.8m✅ Final Answer:
Absolute minimum radius ≈ 129 m.

Design speed (kmph) : 30 40 50 60 70 80 90 100 110.

Radius in (meter): 40 70 100 150 200 260 320 400 440.

Agree @Deepankar.

The Correct ans is 128.84 m.

In the case of the minimum radius or maximum superelevation, we use: (e+f)=v^2/127*R.

And in the case of the maximum radius or minimum super elevation, we use the design superelevation formula i.e. e=v^2 / 225*R.

For absolute minimum or ruling minimum radius we have to use V^2/127(e+f).

Where, V=speed in KMPH, e=given superelevation or according to given terrain condition (as there is none in this case so we HAVE TO assume plain for which it is 7% or 0.07) f = coefficient of lateral friction( 0.15).

R(absolute minimum)= (60)^2/127(0.07+0.15)= 128.84~129m.

Factor 225 as kph, so answer 72.

Agree @Shyamlal.

Can we use e=(0.75V)*2/gr this formula?
r = (0.75*16.67) * 2/9.81 * 0.07,
r = 227.62.

The right value is 128.84 meter.

How can we guess the weather it is a mixed traffic or single traffic. Can anyone explain based on this question?

Option D None of above.

The compensate gradients is 4 degree for, so the radius will be 60 x 4 = 120m.