Highway Intersections - IES Previous Year Questions

1. Consider the following situations:

  1. Traffic volume entering from all roads is less than 3000 vehicles per hour.
  2. Pedestrian volume is high.
  3. Total right turning traffic is high. 
  4. A road in a hilly region. 

A rotary will be more suitable than control by signals, in situations listed against _____ .

[IES 1995]

  1. 1 and 4
  2. 2 and 4
  3. 2 and 3
  4. 1 and 3
Answer: Option D
Explanation:
  • Also, a rotary will be suitable when there is a large area available at a reasonable cost. Hence, unsuitable for hilly regions.
  • Pedestrian traffic must be lower to ensure efficient functioning of a rotary.
As per IRC standards, a rotary is justified,
  • When the total number of vehicles entering from all the roads of the rotary is less than 3000 vehicles per hour.
  • When the intersecting traffic is more than 50% of the total traffic on all the roads.
  • When the fast traffic turning right is at least 30% of the total traffic.

2. Consider the following parameters related to a rotary intersection:

  1. Width of the weaving section
  2. Length of the weaving section
  3. Proportion of weaving traffic
  4. Weaving angle
  5. Width of the carriageway at entry

Capacity is generally expressed in terms of _____ .

[IES 1997]

  1. 1, 2, 3 and 5
  2. 1, 2, and 3
  3. 4 and 5
  4. 1, 2, 3 and 4
Answer: Option A
Explanation:
The capacity of a rotary is given by, Qp =
280 w {1 + (e/w)}{1 - (p/3)} / 1 + (w/L)

Where,
Qp - Capacity of the rotary
w - Width of weaving section
e - Average width of rotary at entry and width of non-weaving section
p - proportion of weaving traffic =
Weaving traffic / Total traffic

L - Length of weaving section

3.  Assertion (A): IRC suggests that the maximum volume of traffic of 3000 vehicles per hour entering from all legs of the rotary intersection can be handled efficiently. 

Reason (R): Traffic rotaries may be provided where the intersecting traffic is about 50% of the total traffic or fast turning traffic is at least 30% of the total traffic.

[IES 1999]

  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 B
Explanation:
As per IRC standards, a rotary cab be provided,
  • When the total number of vehicles entering from all the roads of the rotary is less than 3000 vehicles per hour.
  • When the intersecting traffic is more than 50% of the total traffic on all the roads.
  • When the fast traffic turning right is at least 30% of the total traffic.

4.  Match List-I (Unit) with List-II (Purpose) and select the correct answer using the codes given below the lists:

List-I

  1. Clover leaf interchange
  2. Traffic studies
  3. Rotary island
  4. Road junction approach sign

List-II

  1. Informatory sign
  2. Traffic control device
  3. Traffic flow characteristics
  4. Grade separation

[IES 2005]

Codes: A B C D

  1.  2  1  4  3
  2.  4  1  2  3
  3.  2  3  4  1
  4.  4  3  2  1
Answer: Option D
Explanation:
  • Clover leaf interchange is an example of grade separated intersection.
  • Traffic studies are carried out to analyse the traffic flow characteristics.
  • Rotary island helps to regulate traffic at intersections.
  • Road junction approach sign is an informatory sign.

5.  Which of the following factors are not strictly related to design of traffic rotary intersections ?

  1. Radius of central island
  2. Weaving length
  3. Ramps and interchanges
  4. Acceleration lanes

Select the correct answer using the codes given below:

[IES 2008]

  1. 1 and 4
  2. 2 and 3
  3. 3 and 4
  4. 1 and 2
Answer: Option C
Explanation:
The design of rotary depends on
  • Design speed
  • Shape of central island
  • Radius and width of rotary roadway (the road around the central island will have different radii at different points based on the shape of central island)
  • Weaving angle and weaving distance
  • Width of carriageway at entry and exit
  • Entrance and exit curves
  • Capacity of rotary
  • Camber and super elevation
  • Sight distance
  • Lighting and traffic signs

6.  Which one of the following geometric features requires the magnitudes of weaving angle and weaving distance for its design ?

[IES 2009]

  1. Right-angle intersection
  2. Roundabout
  3. Grade-separated junction
  4. Rotary design
Answer: Option D
Explanation:
The design of rotary depends on
  • Design speed
  • Shape of central island
  • Radius and width of rotary roadway (the road around the central island will have different radii at different points based on the shape of central island)
  • Weaving angle and weaving distance
  • Width of carriageway at entry and exit
  • Entrance and exit curves
  • Capacity of rotary
  • Camber and super elevation
  • Sight distance
  • Lighting and traffic signs

7.  Assertion (A): In an intersection design, the relative speed is dependent on the absolute speed of intersecting vehicles and the angles between them.

Reason (R): When the angle of merging is small, the relative speed will be high.

[IES 2010]

  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:
  • Relative speed is the sum of speeds of approaching vehicles, if the vehicles travel in opposite directions. (or) It is the difference of speeds of vehicles which are travelling in the same direction.
  • The relative speed depends on the absolute speed of intersecting vehicles and the angles between them. The relative speed will be lesser when the merging angle between the intersecting vehicles is small.
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