Horizontal Alignment of Highways - IES Previous Year Questions

1. The maximum super elevation to be provided on a road curve is 1 in 15. If the rate of change of super elevation is specified as 1 in 120 and the road width is 10 m, then the minimum length of the transition curve on either end will be _____ .

[IES 1995]

  1. 30 m
  2. 180 m
  3. 80 m
  4. 125 m
Answer: Option C
Explanation:
  • The minimum length of transition curve, when the pavement is rotated about inner edge is given by,
    L = eNW =
    1 / 15
    x 120 x 10 = 80 m
  • The minimum length of transition curve, when the pavement is rotated about the center is given by,
    L = eN x
    W / 2
    =
    1 / 15
    x 120 x
    10 / 2
    = 40 m
    Here, the minimum length of transition curve will be 80 m.

2.  Assertion (A): For mixed traffic conditions, the super elevation should fully counteract the centrifugal force for the full design speed.

Reason (R): Super elevation needed to maintain the design speed in full may exceed the limiting value of 0.07. Further, as it is not possible to increase the radius, the speed has to be restricted.

[IES 1995]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option D
Explanation:
  • Under mixed flow conditions, the super elevation must counteract the centrifugal force developed due to 75% of the design speed only.
  • The maximum permissible super elevation for plain terrain is 0.07 and coefficient of longitudinal friction is 0.15,
    Hence, e + f = v2/gR
    ⇒ 0.07 + 0.15 = v2/gR
    The above equation provides the permissible speed for the provided super elevation. Since, radius of the curve (R) cannot be changed, the design speed (V) is reduced.

3.  Assertion (A): Rotating parts of the surface of the road with the crown as the pivot is not generally preferred for achieving the needful cant at horizontal curves.

Reason (R): Lowering of the lower edge interferes with the drainage system of the road.

[IES 1996]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option A
Explanation:
When the pavement is rotated with respect to the crown, the inner edge of the pavement goes below the general ground level. This results in drainage problems in areas of heavy rainfall. Hence, this method of attainment of super elevation is generally not preferred.

4.  Assuming the safe stopping sight distance to be 80 m on a flat highway section and with a setback distance of 10 m, what would be the radius of the negotiable horizontal curve ?

[IES 1996]

  1. 80 m
  2. 800 m
  3. 70 m
  4. 160 m
Answer: Option A
Explanation:
Assuming Length of the curve (L) > Stopping Sight Distance (SSD),
Setback distance, m =
S2 / 8R

⇒ 10 =
802 / 8R

⇒ R = 80 m

5.  Assertion (A): It is general practice to provide cant to the road surface with inner edge forming the pivot point.

Reason (R): It does not change center line levels which have already been fixed at the design stage.

[IES 1998]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option C
Explanation:
  • When providing cant, the outer edge of the pavement is raised with respect to the inner edge to avoid drainage problems.
  • When the pavement is rotated with respect to the inner edge, the level at the centre of the pavement raises and hence, it will not remain the same.

6.  For a circular curve of radius 200 m, the coefficient of lateral friction is 0.15 and the design speed is 40 kmph, the equilibrium super elevation (for equal pressure on inner and outer wheel) would be _____ .

[IES 1999]

  1. 4.6
  2. 6.3
  3. 21.3
  4. 7
Answer: Option B
Explanation:
Design speed, v = 40kmph = 11.11 m/s
The equilibrium super elevation, eequil =
v2 / gR
=
11.112 / 9.81 x 200

⇒ eequil = 0.063 (or) 6.3%

7.  A horizontal curve of 480 m for 7.5 m two-lane road is to be designed for a speed of 80 kmph. The raising of the outer edge of the pavement with respect to the inner edge to cater to the mixed traffic condition is _____ .

[IES 2000]

  1. 0.24 m
  2. 0.27 m
  3. 0.22 m
  4. 0.14 m
Answer: *
Explanation:
Design speed, v = 800 kmph = 22.22 m/s
Under mixed traffic condition, Super elevation e =
(0.75v)2 / gR

⇒ e =
(0.75 x 22.22)2 / 9.81 x 480

⇒ e = 0.059 < e max (0.07 for plain terrain)
Hence, super elevation to be provided, e = 0.059 m
Now, the raising of outer edge with respect to inner edge = eW = 0.059 x 7.5 = 0.44 m

8.  Assertion (A): When a sharp horizontal curve is to be introduced on a road which already has the maximum permissible gradient, the gradient should be decreased.

Reason (R): The gradient should be decreased to compensate for the loss of tractive effort due to the introduction of sharp horizontal curve on the road.

[IES 2001]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option A
Explanation:
  • There will be loss of tractive effort when a vehicle approaches a gradient or a horizontal curve. The permissible loss in tractive effort is attained when a vehicle travels under maximum permissible gradient.
  • In addition to the gradient, if a horizontal curve is also provided, the gradient has to be reduced in order to keep the loss of tractive effort under the permissible value.
Hence, grade compensation is provided when a vehicle approaches a horizontal curve with maximum permissible gradient.

9.  Assertion (A): The centrifugal ratio decreases along the length of the transition curve.

Reason (R): The super elevation increases along the length of the transition curve.

[IES 2001]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option D
Explanation:
  • The length of transition curve, L = eNW
    Here, e ∝ L. Hence, super elevation increases along the length of the curve.
  • Centrifugal ratio,
    P / W
    = e + f.
    As super elevation increases along the length of the transition curve, the centrifugal ratio also increases along the length of transition curve.

10.  Assertion (A): A skillful highway designer ‘builds in’ speed control at critical locations on horizontal curves rather than increase the superelevation.

Reason (R): A driver slows down on horizontal curve due to feeling of discomfort because of increase in side friction with reduced super elevation.

[IES 2002]

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not a correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer: Option C
Explanation:
  • Increasing the super elevation will increase the chance of inward overturning of slow moving vehicles. Hence, a skilled highway designer will include speed control rather than increasing the super elevation.
  • The side friction does not increase with decrease in super elevation.
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