Your Answer : (Not Answered)

Correct Answer : B

The deviation angle is 11/600.

The deviation angle is the algebraic difference of the gradients. An ascending gradient is positive and a descending one negative:

\[ \begin{aligned} N &= \frac{1}{100} - \left(-\frac{1}{120}\right) \\ &= \frac{6 + 5}{600} = \frac{11}{600} \end{aligned} \]

Subtracting the magnitudes instead gives \(\frac{1}{600}\), the trap for forgetting the sign. \(\frac{1}{12000}\) is the product of the two gradients, which has no meaning here.

Your Answer : (Not Answered)

Correct Answer : C

The IRC ruling gradient in plain terrain is 1 in 30.

IRC recommends, for plain and rolling terrain, a ruling gradient of 3.3 per cent (1 in 30), a limiting gradient of 5 per cent (1 in 20) and an exceptional gradient of 6.7 per cent (1 in 15). The ruling gradient is the one adopted for design wherever possible.

1 in 20 and 1 in 15 are the limiting and exceptional values for plains, and 1 in 45 is flatter than any IRC design category.

Your Answer : (Not Answered)

Correct Answer : B

The maximum grade compensation is 75/R per cent.

On a horizontal curve, extra tractive effort is needed to overcome curve resistance, so IRC requires the gradient to be eased. The grade compensation is (30 + R)/R per cent, subject to a maximum of 75/R per cent, where R is the radius in metres. Compensation is not needed for gradients flatter than 4 per cent.

50/R, 100/R and 125/R are not the IRC limit.

Your Answer : (Not Answered)

Correct Answer : B

The least count of the penetrometer is 0.1 mm.

In the penetration test, a standard needle under a 100 g load is allowed to penetrate a bitumen sample at 25°C for 5 seconds. Penetration is reported in units of 0.1 mm (1/10 mm), so the dial reads to 0.1 mm; a bitumen of grade 80/100 penetrates 8 to 10 mm.

1 mm would be too coarse to distinguish grades, while 0.01 mm and 0.001 mm are finer than the test reports.

Your Answer : (Not Answered)

Correct Answer : B

The maximum water content in bitumen is 0.2% by weight.

Bitumen should be practically free of water, because water causes foaming when the bitumen is heated and weakens its bond with aggregate. The specifications limit water content to 0.2 percent by weight, tested by the Dean and Stark distillation method.

0.1 percent is stricter than the limit, and 1 and 2 percent would allow enough water to cause foaming in heating.

Your Answer : (Not Answered)

Correct Answer : B

The mix is a Gap-graded mix.

A gap-graded bituminous mix leaves out some aggregate sizes in the gradation. The larger aggregate particles float in a rich mortar of fines and binder, which gives the mix good fatigue resistance and tensile strength, as in stone matrix and rolled asphalt types.

A well-graded mix contains all sizes in a continuous gradation, an open-graded mix has few fines and many voids for drainage, and 'unbound' material has no binder at all.

Your Answer : (Not Answered)

Correct Answer : C

The IRC minimum length for plain terrain is \(2.7\ V^{2}/R\).

IRC gives the minimum length of a transition curve from the empirical formula:

\[ L_s = \frac{2.7\,V^{2}}{R} \]

for plain and rolling terrain (and \(V^{2}/R\) for mountainous terrain), with V in km/h and R in metres; the design length is the larger of this and the lengths from the rate of change of centrifugal acceleration and the rate of introducing superelevation. \(0.0215\ V^{3}/CR\) is the centrifugal acceleration criterion, not the plain-terrain minimum, and the other two options are not IRC formulae.

Your Answer : (Not Answered)

Correct Answer : B

Psychological widening is \(V/9.5\sqrt{R}\).

On curves, drivers tend to keep a greater clearance from the vehicle alongside, so IRC adds a psychological widening in metres:

\[ W_{ps} = \frac{V}{9.5\sqrt{R}} \]

with V in km/h and R in metres. The total extra width is this plus the mechanical widening \(nl^{2}/2R\), which allows for the rear wheels tracking inside the front wheels; that formula, with n lanes and wheelbase l, is the trap option. \(V/2R\) and \(nl^{2}/R\) are not standard forms.

Your Answer : (Not Answered)

Correct Answer : B

The shift is \(L^2/24R\).

When a transition curve is inserted, the circular curve has to be moved inward by the shift

\[ S = \frac{L^2}{24R} \]

where L is the length of the transition curve and R the radius of the circular curve. (The stem calls L the long chord.) \(L^2/6R\) is the offset at the end of the transition curve, four times the shift, and \(L^2/2R\) is the offset of a simple curve, so they are the usual traps.

Your Answer : (Not Answered)

Correct Answer : B

The convexity is called the Camber.

Camber (cross slope) is the slope given to the carriageway from the crown to the edges, so that rainwater drains off the surface quickly. It is usually shaped as two straight slopes or a parabola.

Gradient is the longitudinal slope along the road, kerbs are the raised edging along the pavement, and a vertical curve joins two different gradients.

Your Answer : (Not Answered)

Correct Answer : B

The maximum camber for an earth road is 1 in 25.

Camber depends on the surface and the rainfall: the more pervious and rough the surface, the steeper the camber needed to shed water. IRC recommends 3 to 4 percent for earth roads, the steepest of all surfaces, so the maximum is 4 percent, or 1 in 25.

1 in 40 (2.5 percent) suits a paved or gravel surface, and 1 in 20 (5 percent) and 1 in 16.7 (6 percent) are steeper than the recommended range and would cause erosion of the road surface.

Your Answer : (Not Answered)

Correct Answer : A

As speed increases, the longitudinal friction coefficient Decreases.

At higher speeds the tyre has less time to grip the micro-texture of the pavement and, on wet roads, a film of water builds up under the tyre, so the available friction falls. IRC therefore uses longitudinal friction coefficients of about 0.35 to 0.40 for stopping sight distance, the lower values for higher design speeds.

Friction does not stay constant or rise with speed; that is why stopping distances increase faster than speed itself.

Your Answer : (Not Answered)

Correct Answer : A

The intermediate sight distance is 240 m.

By IRC practice, intermediate sight distance is twice the safe stopping sight distance.

\[ \begin{aligned} \text{ISD} &= 2 \times \text{SSD} \\ &= 2 \times 120 = 240\ \text{m} \end{aligned} \]

The passing (overtaking) distance of 250 m is not used. 500 m is twice the passing distance, 250 m is the passing distance itself, and 120 m is the stopping distance.

Your Answer : (Not Answered)

Correct Answer : D

As per IRC 66, intermediate sight distance is 2 SSD.

Intermediate sight distance is twice the safe stopping sight distance. It is provided on two-lane roads where full overtaking sight distance cannot be given, so that drivers have a reasonable chance to overtake with caution.

(SSD + OSD)/2 and (OSD - SSD)/2 are not defined sight distances, and 2 OSD would be longer than the overtaking distance itself, which defeats the purpose of an intermediate value.

Your Answer : (Not Answered)

Correct Answer : C

The stopping sight distance is 61.4 m for a two-way road with two lanes. On a single-lane road with two-way traffic two vehicles approaching each other on the same lane must each be able to stop before they meet, so the sight distance required is double that for a single vehicle:

The value of 61.4 m is the case already given for two lanes, and 30.7 m is half of it, which is the wrong way round. The value 150.8 m does not follow from the data.

Your Answer : (Not Answered)

Correct Answer : C

The key marks the option listing sources of income, vehicle registration and local taxes as the one which is not an economic study during planning surveys. The economic studies of highway planning cover the per capita income, the trend of population growth, and the industrial and agricultural products of the area listed in classified groups, since these show the traffic that the road will generate. I have followed the official key; the third option is the one that the body treats as outside the economic studies.

Your Answer : (Not Answered)

Correct Answer : C

The key marks both statements as correct. The first limits the liquid limit of the fines used in the wearing course of an earth road in a seasonally wet tropical climate to 40 percent, so that the surface does not become sticky and weak when wet. The second limits the wet aggregate impact value to 40 for aggregate in the base and 30 in the surfacing. I could not check the figures in the code text, so this explanation follows the official key.

Your Answer : (Not Answered)

Correct Answer : D

The aggregate impact test measures the toughness of aggregates, their resistance to failure by sudden shock or impact: a standard hammer is dropped on a sample in a mould and the fines produced are weighed. The crushing strength test gives the resistance to a slowly applied compressive load, the Los Angeles test gives resistance to wear (abrasion) by steel balls, and the angularity number test is a measure of the shape (angularity) of the particles. They measure strength, hardness and shape, and not toughness.

Your Answer : (Not Answered)

Correct Answer : A

For cement concrete roads in areas with heavy rainfall, the recommended camber is 1 in 50, which is steeper than the 1 in 60 sometimes allowed in light rain. A cross-slope of this order drains the surface quickly, while a flatter one lets water stand. The values of 1 in 40, 1 in 33 and 1 in 25 are the cambers that are used for lower types of surface such as gravel, WBM and earth roads, which need a steeper slope because they are more permeable and rougher.