Question 1 |

As per the Indian Roads Congress guidelines (IRC 86: 2018), extra widening depends on which of the following parameters?

Horizontal curve radius | |

Superelevation | |

Number of lanes | |

Longitudinal gradient |

Question 1 Explanation:

As per IRC 86: 2018 Clause 8.6 Widening of Carriageway on Curves:

At sharp horizontal curves, it is necessary to widen the carriageway to provide for safe passage of vehicles. The widening required has two components: (i) mechanical widening to components for the extra width occupied by a vehicle on the curve due to tracking of the rare wheels, and (ii) psychological widening to permit easy crossing of vehicles since vehicles in a lane tend to wander more on a curve than on a straight reach.

On two-lane or wider roads, it is necessary that both the above components should be fully catered for so that the lateral clearance between vehicles of curves is maintained equal to the clearance available on straight. Position of single-lane roads however is somewhat different.

Since during crossing maneuvers outer wheels of vehicles have in any case to use the shoulder whether on the straight or on the curve. It is, therefore sufficient on single lane roads if only the mechanical component of widening is taken into account.

Based on the above considerations, the extra width of carriageway to be provided at horizontal curves on single and two-lane roads is given in Table For multi-lane roads, the pavement widening may be calculated by adding half the widening for two-lane roads to each lane.

Table : Extra width of Pavement at Horizontal Curves

At sharp horizontal curves, it is necessary to widen the carriageway to provide for safe passage of vehicles. The widening required has two components: (i) mechanical widening to components for the extra width occupied by a vehicle on the curve due to tracking of the rare wheels, and (ii) psychological widening to permit easy crossing of vehicles since vehicles in a lane tend to wander more on a curve than on a straight reach.

On two-lane or wider roads, it is necessary that both the above components should be fully catered for so that the lateral clearance between vehicles of curves is maintained equal to the clearance available on straight. Position of single-lane roads however is somewhat different.

Since during crossing maneuvers outer wheels of vehicles have in any case to use the shoulder whether on the straight or on the curve. It is, therefore sufficient on single lane roads if only the mechanical component of widening is taken into account.

Based on the above considerations, the extra width of carriageway to be provided at horizontal curves on single and two-lane roads is given in Table For multi-lane roads, the pavement widening may be calculated by adding half the widening for two-lane roads to each lane.

Table : Extra width of Pavement at Horizontal Curves

Question 2 |

Which of the following is equal to the stopping sight distance?

(braking distance required to come to stop) + (distance travelled during the perception- reaction time) | |

(braking distance required to come to stop) - (distance travelled during the perception- reaction time) | |

(braking distance required to come to stop) | |

(distance travelled during the perception- reaction time) |

Question 2 Explanation:

SSD = Braking distance + lag distance

where,

Braking distance = Braking distance required to come to stop

Lag distance = distance travelled during the perception reaction time.

where,

Braking distance = Braking distance required to come to stop

Lag distance = distance travelled during the perception reaction time.

Question 3 |

For a horizontal curve, the radius of a circular curve is obtained as 300 \mathrm{~m} with the design speed as 15 \mathrm{~m} / \mathrm{s}. If the allowable jerk is 0.75 \mathrm{~m} / \mathrm{s}^{3}, what is the minimum length (in \mathrm{m}, in integer) of the transition curve ?

5 | |

10 | |

15 | |

25 |

Question 3 Explanation:

Radius of circular curve (\mathrm{R})=300 \mathrm{~m}

\mathrm{V}_{\mathrm{d}}=15 \mathrm{~m} / \mathrm{s}

Allowable jerk (\mathrm{C})=0.75 \mathrm{~m} / \mathrm{sec}^{3}

\begin{aligned} & \mathrm{L}_{\min }=\frac{\mathrm{v}^{3}}{\mathrm{CR}} \\ & \mathrm{L}_{\min }=\frac{(15)^{3}}{0.75 \times(300)}=15 \mathrm{~m} \end{aligned}

\therefore \quad Minimum length of transition curve =15 \mathrm{~m}.

\mathrm{V}_{\mathrm{d}}=15 \mathrm{~m} / \mathrm{s}

Allowable jerk (\mathrm{C})=0.75 \mathrm{~m} / \mathrm{sec}^{3}

\begin{aligned} & \mathrm{L}_{\min }=\frac{\mathrm{v}^{3}}{\mathrm{CR}} \\ & \mathrm{L}_{\min }=\frac{(15)^{3}}{0.75 \times(300)}=15 \mathrm{~m} \end{aligned}

\therefore \quad Minimum length of transition curve =15 \mathrm{~m}.

Question 4 |

G_{1} and G_{2} are the slopes of the approach and departure grades of a vertical curve, respectively.

Given \left|G_{1}\right| \lt \left|G_{2}\right| and \left|G_{1}\right| \neq\left|G_{2}\right| \neq 0

Statement 1: +G_{1} followed by +G_{2} results in a sag vertical curve.

Statement 2: -G_{1} followed by -G_{2} results in a sag vertical curve.

Statement 3: +G_{1} followed by -G_{2} results in a crest vertical curve.

Which option amongst the following is true?

Given \left|G_{1}\right| \lt \left|G_{2}\right| and \left|G_{1}\right| \neq\left|G_{2}\right| \neq 0

Statement 1: +G_{1} followed by +G_{2} results in a sag vertical curve.

Statement 2: -G_{1} followed by -G_{2} results in a sag vertical curve.

Statement 3: +G_{1} followed by -G_{2} results in a crest vertical curve.

Which option amongst the following is true?

Statement 1 and Statement 3 are correct;
Statement 2 is wrong | |

Statement 1 and Statement 2 are correct;
Statement 3 is wrong | |

Statement 1 is correct; Statement 2 and
Statement 3 are wrong | |

Statement 2 is correct; Statement 1 and
Statement 3 are wrong |

Question 4 Explanation:

Given, \left|G_{1}\right| \lt \left|G_{2}\right| and \left|G_{1}\right| \neq\left|G_{2}\right| \neq 0

Statement 1:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical sag curve.

Statement 2:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical crest curve.

Statement 3:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical crest curve.

Statement 1:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical sag curve.

Statement 2:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical crest curve.

Statement 3:

\left|G_{1}\right| \lt \left|G_{2}\right|

This results in a vertical crest curve.

Question 5 |

A parabolic vertical crest curve connects two road segments with grades +1.0% and -2.0%. If a 200 m stopping sight distance is needed for a driver at a height of 1.2 m to avoid an obstacle of height 0.15 m, then the minimum curve length
should be ______ m. (round off to the nearest integer)

241 | |

365 | |

115 | |

273 |

Question 5 Explanation:

Given that, n_1=+1% and n_2=-2%

n=n_1-n_2=3%

SSD = 200 m

and h_1= 1.2 m and h_2= 0.15 m

as given n_1 up gradient, and n_2 - down gradient.

So curve is summit curve.

Assume L > SSD

\begin{aligned} L &=\frac{NS^2}{2(\sqrt{n_1}+\sqrt{n_2})^2} \\ &= \frac{3}{100} \times \frac{(200)^2}{2 \times (\sqrt{1.2}+\sqrt{0.15})^2}\\ &=272.91>200 \\ L&=272.91m \end{aligned}

n=n_1-n_2=3%

SSD = 200 m

and h_1= 1.2 m and h_2= 0.15 m

as given n_1 up gradient, and n_2 - down gradient.

So curve is summit curve.

Assume L > SSD

\begin{aligned} L &=\frac{NS^2}{2(\sqrt{n_1}+\sqrt{n_2})^2} \\ &= \frac{3}{100} \times \frac{(200)^2}{2 \times (\sqrt{1.2}+\sqrt{0.15})^2}\\ &=272.91>200 \\ L&=272.91m \end{aligned}

There are 5 questions to complete.

Very helpful. Thanku so muchðŸ”¥

Please check the solution of question 28

M= (R-d)-(R-d) cos a/2 For two lane

You are wrong bro !

m= R-(R-d)cos(a/2)

solution is correct.

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