Highway Geometric Design MCQ Quiz in తెలుగు - Objective Question with Answer for Highway Geometric Design - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

Explanation:

Lateral Clearance:

(i) Lateral Clearance is the distance between the extreme edge of the carriageway to the face of the nearest support weather it is a solid abutment, pier, or column.

(ii) Clause 6.1.1 IRC 54:1974 gives clear guidelines regarding the lateral clearance on the single carriageway for different types of roads.​

Explanation:

• The longitudinal friction on the highway for calculation of stopping distance in geometrical design is 0.35 to 0.40.
• Recommended value of the lateral friction coefficient by the Indian Road Congress is 0.15.

Two types of friction generally considered in highway design are as follows:

1. Lateral/Side/Traverse friction: It acts to counter the centrifugal force acting on the tyre in the lateral direction.

Recommended value of lateral friction coefficient by the Indian Road Congress is 0.15.

However, in the case of expressways, it can be reduced even to 0.1 with a design speed of 120 kmph.

2. Longitudinal/Rolling friction: It acts in the rolling direction of tyres of the vehicle.

Recommended value of longitudinal friction by Indian Road Congress are as follows:

Shoulders are provided along the road edge and is intended for accommodation of stopped vehicles, serve as an emergency lane for vehicles and provide lateral support for base and surface courses. The shoulder should be strong enough to bear the weight of a fully-loaded truck even in wet conditions.

The shoulder width should be adequate for giving working space around a stopped vehicle. It is desirable to have a width of 4.6 m for the shoulders. The minimum width of 2.5 m is recommended.

Cross slope for the shoulder is 0.5% steeper than the cross slope of the pavement.

Important Points:

Cross slope to be provided for different types of pavement are as follows:

Explanation:

Recommended standards for building line and control line:

Cross-section of highway with various lines:

Explanation:

Extra widening of road is given by,

We = Wm + Wps

\({W_e} = \frac{{n{l^2}}}{{2R}} + \frac{V}{{9.5\sqrt R }}\)

Where,

Wm = Mechanical widening, Wps = Psychological widening, n = number of lanes, l = length of wheelbase, R = Radius of curve, V = Velocity of vehicle (in kmph)

IRC recommended values of extra widening for single and two-lane pavement are given below:

1) If R > 300 m, then extra widening is not provided.

2) If R < 50 m, Then extra widening is provided at the inner edge.

3) If 50 < R < 300 m, then extra widening is provided at both edges.

Explanation:

Exceptional gradient:

• The exceptional gradient is steeper than the ruling gradient and the limiting gradient 
• It is provided only if the situation is unavoidable. It should not be provided for a length of more than 100 m.
• Critical length of the grade (for exceptional gradient only):
  • Length of road covered by a heavily loaded truck on an ascending gradient without too much reduction in speed. The reduction in speed should not be more than 25 kmph.

Important Points 

Gradient:

• A gradient is the rise or fall along the length of the road with respect to horizontal. It is expressed as 1 in n (1 vertical to n horizontal) or n% i.e. n in 100.
• There are different types of gradients:
  • Ruling gradient: It is the maximum gradient within which the designer wants to design the vertical profile of the road, hence it is known as the design gradient
  • Limiting gradient: It is steeper than the ruling gradient
  • Exceptional gradient: Discuss above
  • Minimum gradient: It is provided along the length of the road from drainage point of view. The minimum gradient for cement concrete drain is 1 in 500.

Gradients for different terrain types:

Concept:

Gradient: Gradient is the rate of rise or falls along the length of the road with respect to horizontal.

Expressed as ‘1' vertical unit to 'N' horizontal units.

Types of Gradient:

i) Ruling gradient:

• The gradient is fixed in such a way that maximum power developed by the engine is equal to the power required to overcome the resistance to the motion on the grade at design speeds.

ii) Limiting gradient:

• A gradient steeper than the ruling gradient which may be used in restricted length, where the ruling gradient is not possible.

iii) Exceptional gradient:

• A gradient steeper than the limiting gradient which may be used in very short stretchers only in an exceptional case.

iv) Floating gradient:

• The gradient on which a motor vehicle moving with a constant speed continues to descend with the same speed without any application of power brakes is called floating gradient i.e the vehicle does not require any tractive effort to maintain the specific speed.

∴ Limiting gradient is the steepest gradient permitted on roads in ordinary conditions and in some extraordinary situations it may be unavoidable to provide still steeper gradients at least for short stretches and in such cases, the steeper gradient up to exceptional gradients may be provided. The ruling gradient or the design gradient is the gradient with which the designer attempts to design the vertical profile of the road.

Note:

Approximate formulas for calculation of set back distance

Case - 1 If the length of the curve > sight distance (SSD)

setback distance, \(m=\frac{s^2}{8R}\) ; R = Radius of curve

Case - 3 If the length of curve < sight distance (SSD)

Setback distance, \(m=\frac{L(2S-L)}{8R}\)

In this out, length of the curve is not given, assuming the next length of the curve is more than SSD.

So, \(\rm{m = \frac{S^2}{8R} \begin{pmatrix} m = 10 \ m \\\ S = 80 \ m \end{pmatrix}}\)

\(10=\frac{(80)^2}{8\times R}\)

We get, R = 80 m

Concept:

Grade Compensation = minimum of \(\left\{ {\frac{{75}}{R},\frac{{30 + R}}{R}} \right\}\)%

Calculation:

Grade Compensation = minimum of \(\left\{ {\frac{{75}}{{200}},\frac{{30 + 200}}{{200}}} \right\}\)

Grade Compensation = minimum of {0.375, 1.15}

Explanation:

Maximum height of crown with respect to edges \( = \frac{W}{{2n}}\)

Where W is the width of the pavement.

Now for high-type bituminous in high rainfall areas, camber provided = 1 in 50, W = 7 m

∴ Maximum height of the crown \(= \frac{{7 \times {{10}^3}}}{{2 \times 50}} = 70\;mm\)

 Maximum height of crown = 0.07 m

Additional Information 

Camber of pavement depends on

• Type of pavement
• The intensity of rainfall (Light/Heavy rain)