Question 1

Crossfall of carriageway – definition of camber In highway cross-section terminology, the convexity provided from the crown to the edges of the pavement to facilitate drainage is called:

Accepted Answer

Introduction / Context: Water must be drained quickly from the pavement surface to avoid skidding, hydroplaning, and moisture damage. The designed crossfall (crown-to-edge slope) is a simple geometric feature that achieves this across all pavement types. Given Data / Assumptions: A crowned carriageway with edges lower than the centerline. Use of standard road crossfall terminology. Concept / Approach: Camber is the intentional transverse slope from the crown toward the edges to shed water. It differs from super-elevation, which is a purposeful banking of the cross-section on horizontal curves to counteract centrifugal effects. Step-by-Step Solution: Identify the function: drainage under rainfall.Recognize geometric form: convex surface, crown at center.Terminology: this is called camber (not super-elevation). Verification / Alternative check: Standard drawings show typical camber values by surface type: earth roads have higher camber; bituminous and concrete have moderate camber. Why Other Options Are Wrong: Super-elevation addresses lateral acceleration on curves; “height of pavement” is not a standard term for crossfall. Common Pitfalls: Confusing camber with super-elevation; specifying excessive camber causing driver discomfort or excessive edge wear. Final Answer: camber

Question 2

Standard equation of the cubic parabola (spiral) transition used on roads For a highway transition curve modeled as a cubic parabola joining a tangent to a circular curve of radius R with transition length L, which of the following is the standard C…

Accepted Answer

Introduction / Context: Highway transition curves are often represented by a cubic parabola (also called a cubic spiral) because it provides a linear rate of change of curvature with length, ensuring comfort and consistent development of centrifugal acceleration and super-elevation. Given Data / Assumptions: Transition curve of length L connecting a tangent to a circular curve of radius R. Local coordinates: x measured along tangent, y as the offset to the transition. Small-angle assumptions applicable to derive a simple polynomial relation. Concept / Approach: For a cubic parabola transition, curvature k varies linearly with arc length s. Using small deflection approximations, the well-known Cartesian form emerges: y = x^3 / (6 R L). This relation is widely used in setting out offsets of a spiral from the initial tangent. Step-by-Step Solution: Take curvature k = s / (R L) so that k increases linearly from 0 to 1/R over length L.Relate small deflections: dy/dx ≈ θ, and dθ/ds = k.Integrating with boundary conditions at x = 0 gives y = x^3 / (6 R L).Therefore, the standard equation is y = x^3 / (6 R L). Verification / Alternative check: At x = L, the offset compares well with tabulated setting-out data for cubic transitions; alternatives with x^2 terms correspond to circular or parabolic approximations not giving linear curvature change. Why Other Options Are Wrong: y = x^2 / (2R) and y = x^2 / (6 R L): quadratic forms relate to simple circular offsets or sag curves, not cubic transitions. y = x^3 / (3 R L): incorrect coefficient; does not match the derived boundary conditions for cubic parabola transitions. Common Pitfalls: Mixing clothoid (Euler spiral) notation with cubic parabola approximations; forgetting unit consistency; using large-angle trigonometry where small-angle assumption was applied. Final Answer: y = x^3 / (6 R L)

Question 3

Recommended camber for earth roads to ensure drainage For road surfaces constructed in earth (earthen roads), which range of camber is generally preferred to quickly drain rainwater while limiting erosion?

Accepted Answer

Introduction / Context: Camber provides the necessary transverse slope for water to run off the road surface. Earth roads are more permeable and susceptible to rutting and erosion, so the camber must be sufficient to shed water without causing discomfort or instability. Given Data / Assumptions: Surface type: earth (unsealed) road. Objective: adequate drainage with reasonable riding comfort. Concept / Approach: Typical practice recommends higher camber for earth roads than for bituminous or concrete pavements. A range of 1 in 20 to 1 in 24 (about 5% to 4.2%) offers a sound balance: swift drainage yet not so steep as to cause lateral instability or edge erosion. Step-by-Step Solution: Identify surface type → earth requires higher camber.Select the commonly recommended range → 1 in 20 to 1 in 24.Confirm that steeper alternatives (e.g., 1 in 10) are excessive for ordinary traffic comfort. Verification / Alternative check: Design guides generally assign maximum camber to earth roads, intermediate to water-bound macadam, and lower to bituminous/concrete. Why Other Options Are Wrong: Steeper ranges (1 in 10–1 in 15) risk rilling/erosion and discomfort; flatter ranges (1 in 30–1 in 48) may drain too slowly on unsealed surfaces. Common Pitfalls: Applying urban paved-road camber values to earth roads; ignoring rainfall intensity and soil erodibility in local adjustments. Final Answer: 1 in 20 to 1 in 24

Question 4

Joints in rigid pavements – preventing compressive stresses Which type of joint is primarily provided in rigid concrete pavements to prevent the build-up of compressive stresses due to temperature rise and slab expansion?

Accepted Answer

Introduction / Context: Concrete expands when heated and contracts when cooled. Because rigid pavements are restrained by adjoining slabs and friction at the base, thermal movements create stresses. Appropriate joints are installed to control these stresses and avoid cracking or blow-ups. Given Data / Assumptions: Rigid pavement slab on subbase. Daily and seasonal temperature changes occur. We seek the joint that prevents compressive stress buildup. Concept / Approach: Expansion joints provide a gap (often with filler and sealant) that closes when the slab expands, thereby preventing compressive stress accumulation between slabs or at abutments. Contraction joints, by contrast, are intended to control tensile cracking on cooling by creating a weakened plane. Step-by-Step Solution: Identify stress type to be prevented → compressive stress during heating/expansion.Select joint that accommodates expansion → expansion joint.Therefore, the correct choice is expansion joint. Verification / Alternative check: Design standards specify spacing and widths for expansion joints in longer slabs or at fixed structures (bridges, culverts) to relieve compression. Why Other Options Are Wrong: Contraction joints address tensile stresses on cooling; hinged joints are structural detailing concepts and not the primary device for temperature compression relief in pavements. Common Pitfalls: Overusing expansion joints where contraction joints suffice; poor sealing leading to water ingress and pumping. Final Answer: expansion joint

Question 5

Selecting highway alignment in hilly terrain – primary control features In mountainous regions, the alignment of a highway is most fundamentally decided based on which topographic feature?

Accepted Answer

Introduction / Context: Highway alignment in hilly and mountainous terrain must reconcile geometric design needs with topography, geology, and construction costs. While many constraints exist, the fundamental control often comes from the locations where a ridge can be crossed efficiently. Given Data / Assumptions: Terrain: hilly or mountainous. Key objective: achieve feasible gradients and minimum earthworks. Concept / Approach: Saddles and passes are the naturally lowest crossing points along ridgelines. Choosing an alignment that threads these locations reduces the summit levels to be negotiated, keeps gradients reasonable, and minimizes excessive cutting or tunneling. Other factors (river crossings, unstable areas, hard rock) influence local adjustments, but the controlling decision is usually the choice of pass. Step-by-Step Solution: Map ridge lines and identify saddles/passes.Connect valleys using these low points to hold ruling gradients.Iterate to avoid unstable slopes and excessive crossings where practical.Therefore, the primary determinant is the selection of saddles or passes. Verification / Alternative check: Historical mountain roads and modern highways alike are laid through natural passes to minimize climb and earthwork, confirming the primacy of this criterion. Why Other Options Are Wrong: Hard cutting, river crossings, and unstable areas are important constraints to mitigate, but they do not by themselves dictate the overarching alignment like the availability of a pass does. Common Pitfalls: Overfocusing on minimizing distance instead of gradient; neglecting geohazard mapping when selecting passes. Final Answer: saddles or passes

Question 6

Highway alignment and geometry: identify the incorrect statement about providing straight, horizontal, and vertical elements on highways.

Accepted Answer

Introduction / Context: Highway alignment and geometric design must reconcile safety, comfort, topography, and economy. Real-world roads rarely run as perfect straight lines for long distances; instead, they combine tangents with horizontal and vertical curves to achieve safe sight distance, drainage, and earthwork balance. Given Data / Assumptions: The statements compare straight alignments with the use of horizontal and vertical curves. Standard practice follows geometric design standards (e.g., sight distance, super-elevation, grade). No special constraints such as tunnels or bridges override normal design logic. Concept / Approach: Horizontal curves (circular with transition) connect tangents and control lateral acceleration, while vertical curves (summit/valley) smoothly join grades to maintain stopping-sight distance and riding comfort. Continuous straight lines are neither typical nor desirable over varied terrain because they would often violate these requirements. Step-by-Step Solution: Assess each statement against standard practice.(a) “Always constructed in straight line” is false; curves are routinely provided.(b), (c), and (d) are true because both horizontal and vertical curves are integral parts of highway design. Verification / Alternative check: Review any national geometric design manual: you will find minimum radii for horizontal curves, criteria for summit/valley curves, and transition lengths, confirming that curves are essential features. Why Other Options Are Wrong: (b) True: horizontal curves are standard. (c) True: vertical curves join grades. (d) True: both types are routinely combined on most alignments. Common Pitfalls: Assuming long straight stretches are “safer.” Excessively long tangents can reduce driver alertness and may not meet topographic constraints or sight-distance needs at crests/sags. Final Answer: Highways are always constructed in straight line

Question 7

Highway geometric design: the recommended method used to set out a lemniscate transition curve in the field is which of the following?

Accepted Answer

Introduction / Context: Lemniscate transition curves are used in highway and railway design when a more gradual change in curvature than a simple spiral is desired. Setting out such curves demands a method that matches their polar form so that the field layout remains accurate and efficient. Given Data / Assumptions: A lemniscate has a mathematical form naturally described in polar coordinates. Surveyors need a practical method to mark points along the curve from a reference tangent point. Options include offset and deflection-angle methods. Concept / Approach: Because the radius vector and polar angle vary together along a lemniscate, the polar deflection-angle method provides a direct relationship between angle set on a theodolite and the distance along the radius vector, giving better fidelity than simple perpendicular or radial offsets that suit circular or parabolic forms. Step-by-Step Solution: Select the tangent point as origin; establish the initial tangent direction.Compute polar deflection angles and corresponding radial distances for a series of stations along the lemniscate.Set out each point by turning the computed polar deflection angle and measuring the radius distance. Verification / Alternative check: Comparing coordinates obtained via polar deflection with analytical curve equations confirms that the points lie accurately on the intended lemniscate. Why Other Options Are Wrong: Perpendicular or radial offset tables are more suitable for circular or parabolic curves; plain “deflection angles” without polar formulation do not fully exploit the lemniscate’s polar nature. Common Pitfalls: Using offset methods calibrated for spirals or circles can introduce fitting errors on a lemniscate; maintaining angular accuracy is crucial. Final Answer: polar deflection angles.

Question 8

Super-elevation policy in snow-bound regions: what should be taken as the practical upper limit for super-elevation on such roads to reduce skidding risk?

Accepted Answer

Introduction / Context: Super-elevation (crossfall on curves) counteracts lateral acceleration. In snow-bound areas, excessive super-elevation can increase skidding risk on icy surfaces, particularly toward the valley side on hill roads. Hence, a conservative practical upper limit is adopted. Given Data / Assumptions: Road experiences snow/ice conditions for part of the year. Friction is significantly reduced during winter. Safety and vehicle stability govern the choice of maximum super-elevation. Concept / Approach: With reduced friction, lateral stability must be ensured without creating a crossfall so steep that vehicles lose lateral control. A cap around 7% is a widely accepted limit in snow-bound practice, balancing centripetal demand and skid resistance. Step-by-Step Solution: Recognize that higher super-elevation improves balance on dry roads but can be unsafe on ice.Adopt a lower cap in snow-bound regions; 7% is the practical upper limit used in many design guides.Hence select 7% from the options. Verification / Alternative check: Safety audits and winter performance records show that limiting super-elevation reduces outward skidding events on icy curves. Why Other Options Are Wrong: 15%, 12%, and 10% are too steep for low-friction, icy conditions; 6% is more conservative than typical practice but may be unnecessarily restrictive for some sites. Common Pitfalls: Applying general maximum super-elevation without considering climate; ignoring the friction reduction due to snow and ice. Final Answer: 7%

Question 9

Transition-to-circle junction: if L is the length of the transition curve on each side and R is the radius of the circular curve, what is the maximum deflection angle (with the tangent) to the junction point of transition and circle?

Accepted Answer

Introduction / Context: Transition curves provide a gradual change of curvature between tangent and a circular curve, improving comfort and safety. Survey layout often uses the deflection angle from the tangent to locate the end of transition (junction with the circular arc). Given Data / Assumptions: Single transition of length L leads into a circular curve of radius R. We require the deflection from tangent to the transition–circle junction. Standard spiral/transition geometry conventions apply. Concept / Approach: For common transitions (e.g., spiral approximation), the angle between the tangent and the end of transition is approximately L/(2R) radians. This comes from the integral relation between curvature and length and is a well-known field formula for setting out. Step-by-Step Solution: Curvature increases linearly along the transition.Average curvature over the transition = (0 + 1/R) / 2 = 1/(2R).Deflection angle = average curvature * length = L * 1/(2R) = L/(2R). Verification / Alternative check: Check against detailed spiral equations; the commonly used approximation for fieldwork yields the same result. Why Other Options Are Wrong: L/R overestimates; L/3R and L/4R underestimate the standard transition deflection; “none of these” is incorrect because L/2R is correct. Common Pitfalls: Mixing total central angle of curve with end-of-transition deflection; unit confusion (radians vs degrees). Final Answer: L/2R

Question 10

History of road development in India: the year in which the Indian Roads Congress (IRC) was founded and established its headquarters at New Delhi is

Accepted Answer

Introduction / Context: The Indian Roads Congress (IRC) is the apex technical body for highway engineering in India. Knowing its origin helps contextualize the development of standards and best practices in the country’s road sector. Given Data / Assumptions: The question asks specifically for the founding year and establishment of headquarters at New Delhi. Options list plausible years around the pre- and post-independence era. Concept / Approach: Historically, the IRC was formed to unify and standardize road engineering practice across provinces and states, providing codes, guidelines, and recommendations for geometric design, materials, bridges, pavements, and traffic engineering. Step-by-Step Solution: Recall key milestones: the IRC was founded in the interwar period.Among the options, 1934 is the recognized founding year with HQ in New Delhi.Select 1934 as the correct answer. Verification / Alternative check: Standard references in highway engineering texts list 1934 as the IRC’s founding year, with HQ at New Delhi. Why Other Options Are Wrong: 1924, 1927, and 1930 precede the actual founding; 1942 is later than the documented establishment. Common Pitfalls: Confusing IRC’s founding with other committees (e.g., Jayakar Committee) or with later code publication dates. Final Answer: 1934

Question 11

Rigid pavement longitudinal joint design: with pavement slab width 7.5 m, thickness 20 cm, and working stress 1400 kg/cm², what is a reasonable spacing for 10 mm tie bars to keep joints tight under service?

Accepted Answer

Introduction / Context: Tie bars hold longitudinal joints of concrete pavements tightly closed, preventing lane separation due to temperature and shrinkage. Their spacing depends on bar diameter, slab thickness, joint working stress, and expected tensile demand from slab movements. Given Data / Assumptions: Slab width = 7.5 m; thickness = 20 cm. Tie bar diameter = 10 mm; working stress = 1400 kg/cm². Objective: reasonable, standard-practice spacing for service conditions. Concept / Approach: A typical approach distributes joint traction demand among multiple bars so the steel stress does not exceed the working limit while offering adequate bond length. For 10 mm bars in 20 cm slabs, spacings on the order of 25–40 cm are commonly adopted; 30 cm is a widely used practical value balancing steel quantity and performance. Step-by-Step Solution: Estimate joint force demand from slab shrinkage/temperature pull.Choose a bar size and allowable stress → 10 mm at 1400 kg/cm².Adopt a spacing near 0.30 m that has proven satisfactory for 20 cm slabs in practice. Verification / Alternative check: Comparing to standard design tables shows 10–12 mm bars at 0.25–0.40 m spacing are typical for 18–22 cm slabs; 0.30 m lies centrally in that range. Why Other Options Are Wrong: 10 cm and 20 cm are uneconomical; 40–50 cm may permit excessive joint opening and stress in bars under temperature drop. Common Pitfalls: Confusing tie bars (for longitudinal joints) with dowel bars (for transverse load transfer); ignoring bond and development length requirements. Final Answer: 30 cm

Question 12

Length of transition required for super-elevation development: a 7 m wide road requires a maximum super-elevation of 1 in 15, and the rate of change of super-elevation is 1 in 150. What is the maximum transition length to be provided at either end?

Accepted Answer

Introduction / Context: Transition length is needed to rotate the roadway from normal camber to full super-elevation smoothly, ensuring comfort and safety. The “rate of change of super-elevation” specifies how quickly crossfall may be introduced. Given Data / Assumptions: Roadway width b = 7 m. Maximum super-elevation e = 1/15. Rate of change (run-out) N = 150 → length per unit crossfall change. Concept / Approach: Length L to develop full super-elevation is calculated as L = N * b * e. This formula represents the distance required so that the edge level difference b * e is achieved at the permitted rate N (i.e., 1 vertical in N horizontal). Step-by-Step Solution: Compute edge level difference: b * e = 7 * (1/15) = 7/15 m.Compute L: L = N * b * e = 150 * 7/15 = 10 * 7 = 70 m.Select 70 m as the required transition length at either end. Verification / Alternative check: A quick proportional check: if N = 150 per unit rise and required rise is 7/15 ≈ 0.467 m, then 150 * 0.467 ≈ 70 m, confirming the arithmetic. Why Other Options Are Wrong: 65 m and 75–90 m do not match the product N * b * e and would either over- or under-provide the transition. Common Pitfalls: Using the carriageway half-width instead of full width; mixing up e as a percentage versus a ratio. Final Answer: 70 m

Question 13

Effects of excessive camber on pavements: which of the following may occur if the camber (crossfall) provided is unnecessarily high?

Accepted Answer

Introduction / Context: Camber provides crossfall for surface drainage. While necessary, excessive camber can produce undesirable structural and operational effects on the pavement and adjacent shoulders (berms). Given Data / Assumptions: Pavement has a camber larger than recommended for the surface type and rainfall. Vehicles operate at representative speeds. Berms and drainage are typical of rural highways. Concept / Approach: Too large a crossfall pushes water and traffic laterally too aggressively. Water concentrates at edges, accelerating erosion; vehicles experience lateral component of gravity that can cause outward skidding; the crown region carries more compression and may ravel or crack due to thin water film movement. Step-by-Step Solution: Identify issues caused by excessive crossfall: poor ride, instability, edge distress.Relate hydraulics: faster runoff near edges erodes berms and weakens shoulders.Relate traffic dynamics: lateral component encourages outward slip at speed, especially on low-friction surfaces. Verification / Alternative check: Field inspections correlate over-cambered sections with edge raveling, berm gullying, and centerline distress due to uneven load distribution and drainage patterns. Why Other Options Are Wrong: Each of (a), (b), and (c) are valid individual consequences; therefore “all the above” best captures the full effect set. Common Pitfalls: Using a “one size fits all” camber; not adjusting camber for surface type (e.g., CC vs bituminous) and rainfall intensity. Final Answer: all the above.

Question 14

Super-elevation computation from crossfall: a 12.5 m wide carriageway has its outer edge 50 cm higher than the inner edge. What is the required super-elevation expressed as a slope ratio?

Accepted Answer

Introduction / Context: Super-elevation is the upward transverse inclination provided to counteract centrifugal effects on curves. It is commonly specified as a slope ratio (1 vertical in N horizontal) or as a percentage. Given Data / Assumptions: Carriageway width (run) = 12.5 m. Height difference (rise) between outer and inner edges = 50 cm = 0.50 m. Uniform crossfall assumed across the width. Concept / Approach: Super-elevation e (as a ratio) equals rise divided by run. Converting the numeric result into the common “1 in N” form helps compare with standards and check reasonableness. Step-by-Step Solution: Compute e = rise / run = 0.50 / 12.5 = 0.04.Express as a ratio: 0.04 = 1 / 25 → “1 in 25”.Check plausibility: 4% is a typical, moderate super-elevation value. Verification / Alternative check: Convert to percent: 0.04 * 100 = 4%. Compare to usual caps (e.g., 7–10% depending on context) to verify the value is realistic. Why Other Options Are Wrong: (a) “50 cm” is not a slope; (c) 1 in 400 equals 0.25%, far too small; (d) 1 in 40 equals 2.5%; (e) 1 in 24 ≈ 4.17% and does not match the computed value exactly. Common Pitfalls: Mistaking carriageway width with lane width; mixing units (centimetres and metres) without conversion. Final Answer: 1 in 25

Question 15

Four-lane divided highways: To prevent head-on collisions between vehicles moving in opposite directions, which measure is primarily adopted on such roads?

Accepted Answer

Introduction / Context: Head-on collisions are among the most severe crash types because closing speeds are high. Highway engineers therefore design four-lane facilities as divided carriageways so opposing streams are fully separated. The question asks which measure specifically addresses head-on collisions on four-lane roads. Given Data / Assumptions: A four-lane road carries two lanes in each direction. Opposing streams are to be separated to prevent encroachment into the opposite carriageway. Standard traffic control devices like markings may supplement, but not replace, physical separation for high-speed facilities. Concept / Approach: Centerline (or lane) markings provide guidance but cannot physically block errant vehicles. A raised, landscaped, or barrier median forms a continuous longitudinal separator. This median (also called a physical divider) is the primary design element to prevent head-on conflicts by eliminating opposing traffic face-to-face interaction on the same carriageway. Step-by-Step Solution: Identify the crash mode → head-on collision between opposing directions.Map countermeasures → guidance (markings), channelization (area dividers), and separation (medians/physical dividers).Select the measure that physically separates opposing streams → a wide or barrier median. Verification / Alternative check: Design manuals for divided highways emphasize a central median or continuous longitudinal barrier as the definitive treatment for eliminating head-on conflicts on multi-lane high-speed facilities. Markings alone are insufficient at higher speeds or volumes. Why Other Options Are Wrong: Markings on the road: provide delineation but no physical separation; cannot reliably prevent head-on crashes. Area dividers: a vague term for pavement markings/islands; not a continuous physical separator. None of these: incorrect because medians are the standard solution. Common Pitfalls: Confusing lane markings with medians; markings help guidance, not physical crash prevention. Assuming urban channelization islands are equivalent to highway medians; islands are intermittent and local. Final Answer: Medians of wide area are provided.

Question 16

Hilly road location: The gradients adopted on trace cuts for hill roads are generally kept how, relative to the ruling gradient?

Accepted Answer

Introduction / Context: During reconnaissance and preliminary location of hill roads, engineers cut narrow trace lines along hill slopes to test feasible alignments. The gradient along these traces must permit safe movement of survey teams, trial vehicles, and construction equipment while reflecting practical operational gradients. Given Data / Assumptions: A ruling gradient is the desirable maximum gradient used for most of the route under normal conditions. Trace cuts are temporary alignments used for exploration and preliminary works. Safety and ease of movement are priorities during this stage. Concept / Approach: Since trace cuts precede final formation, they should not strain vehicles and equipment. Therefore, designers keep them easier (flatter) than the ruling gradient to allow for uncertainties, rough surfaces, and maneuvering space. A typical thumb rule is making them 10% to 20% flatter than the ruling value. Step-by-Step Solution: State the base target → ruling gradient for hill roads.Apply trace-cut practice → provide additional margin for safety and access.Select the stated margin → 10% to 20% easier than the ruling gradient. Verification / Alternative check: Field practice references and manuals on hill road location consistently recommend easing trace cut gradients to account for temporary surfaces and limited traction. Why Other Options Are Wrong: Equal to ruling gradient: leaves no buffer for temporary, rough conditions. 10%–20% steeper: unsafe and operationally difficult on provisional paths. None of these: incorrect because a standard easing margin is used. Common Pitfalls: Mistaking trace-cut guidance for final formation gradient criteria. Final Answer: 10% to 20% easier (flatter) than the ruling gradient.

Question 17

Right-of-way (ROW) in open country: The normal road land width to be acquired for a National or State Highway in open areas should be approximately what?

Accepted Answer

Introduction / Context: Right-of-way (ROW) is the width of land permanently acquired for a highway. It must contain the carriageway, shoulders, side slopes, drainage, utilities, future widening, and safety zones. In open (non-urban) areas, wider ROW is preferred because land acquisition is comparatively feasible and future expansion can be planned economically. Given Data / Assumptions: Facility type: National or State Highway. Location: open areas (rural), not constrained by dense development. Design requires present and future needs to be accommodated. Concept / Approach: Traditional Indian practice has adopted a typical ROW of about 45 m in open country for higher-class highways, allowing carriageway, shoulders, side drains, landscaping, median (if divided), and future widening (e.g., from 2-lane to 4-lane). Narrower widths are used in built-up or constrained corridors, but not as a norm in open terrain for NH/SH. Step-by-Step Reasoning: Identify facility and terrain → NH/SH in open areas.Recall normal ROW guide value → ≈ 45 m.Select the matching option → 45 m. Verification / Alternative check: Feasibility and DPR templates typically adopt 45 m in rural stretches unless special environmental or land constraints exist, in which case project-specific values are justified. Why Other Options Are Wrong: 30 m, 24 m, 20 m: more common in urban/built-up areas or constrained corridors; insufficient for long-term expansion in open terrain. Common Pitfalls: Confusing rural ROW with urban right-of-way or only carriageway width; ROW is much larger than paved width. Final Answer: 45 m.

Question 18

Rigid pavement sizing (interior case): For a cement concrete pavement with a design wheel load of 6300 kg and a permissible flexural stress of 21 kg/cm², what is the approximate interior slab thickness?

Accepted Answer

Introduction / Context: Slab thickness in cement concrete pavements is governed by flexural (tensile) stress induced by wheel loads. For the interior loading condition, the slab is fully surrounded by concrete, usually making it less critical than edge or corner loading. The question asks for a practical interior thickness corresponding to a moderate wheel load and a given allowable flexural stress. Given Data / Assumptions: Design wheel load W = 6300 kg. Permissible flexural stress σ_allow = 21 kg/cm². Interior loading condition (not edge/corner). Conventional material and support conditions typical of highway rigid pavements. Concept / Approach: Interior stresses are checked using established rigid pavement analysis (e.g., Westergaard-based relations or charts) correlating load, contact area, subgrade reaction, and slab stiffness. For standard ranges of support and materials, charts/tables map the permissible stress to a required slab thickness. A wheel load of about 6.3 tonnes (single wheel 6.3 kN*1000/9.81 ≈ 61.8 kN; using classic highway units) with 21 kg/cm² allowable flexural stress leads to interior thickness near the lower end of typical highway slabs. Step-by-Step Solution (Conceptual): Relate load W and stress capacity σ_allow using interior-load design charts.Account for contact area and typical subgrade reaction; interior condition is least severe.Read off the approximate thickness matching σ_allow = 21 kg/cm² → around 0.17 m. Verification / Alternative check: Pavement design examples with similar wheel loads and flexural strengths frequently yield slab thickness between 15 cm and 20 cm for interior checks; 17 cm is a representative, economical value for interior locations (edge/corner checks generally control higher thickness when included). Why Other Options Are Wrong: 25.5–50.0 cm: far thicker than typical for the stated load and stress limit; uneconomical. 34.0–50.0 cm options match heavy-duty industrial or airfield slabs, not standard road interior cases. Common Pitfalls: Using corner-load thickness for interior condition; corner is more critical and yields greater thickness than interior. Final Answer: 17.0 cm.

Question 19

Terrain classification by cross slope: If the natural cross slope of a country is up to 10%, the terrain is classified as what for highway planning purposes?

Accepted Answer

Introduction / Context: Terrain classification affects design speed, gradient, curvature, and cost of a highway. Standard categories are based on the natural ground cross slope, which influences earthwork volumes and alignment flexibility. Given Data / Assumptions: Cross slope threshold up to 10%. Conventional Indian practice for terrain classes. Used for geometric design and project costing. Concept / Approach: Typical bands are: Plain (0–10%), Rolling (10–25%), Mountainous (25–60%), and Steep (>60%). These reflect construction challenges and achievable design speeds. At up to 10% cross fall, the alignment can generally be laid with modest earthwork and mild gradients—classified as plain terrain. Step-by-Step Reasoning: Compare the given cross slope (≤10%) to terrain bands.Identify corresponding class → Plain.Confirm applicability to design standards and cost factors. Verification / Alternative check: Planning guidelines and geometric design manuals use these bands to set base design speeds and gradient limits; up to 10% clearly falls in the Plain category. Why Other Options Are Wrong: Rolling, Mountainous, Steep: correspond to greater cross slopes producing tighter curves and steeper grades. Common Pitfalls: Interpreting longitudinal gradient limits as terrain class; classification is by natural cross slope, not designed grade. Final Answer: Plain.

Question 20

Traffic forecasting: If the present Average Daily Traffic (ADT) is 5000 vehicles and the annual growth rate is 10%, what is the average daily flow after 5 years (geometric growth)?

Accepted Answer

Introduction / Context: Traffic forecasting is essential for capacity analysis and pavement design. When growth is compounded annually, future ADT is obtained using geometric progression. This quick computation feeds into design year volumes and equivalent axle load calculations. Given Data / Assumptions: Current ADT (A₀) = 5000 vehicles/day. Annual growth rate g = 10% = 0.10. Time horizon n = 5 years. Use geometric growth (compounded annually). Concept / Approach: The geometric growth formula for average daily traffic after n years is Aₙ = A₀ * (1 + g)^n. Substitute the given values and compute to the nearest 10 vehicles (as in the options). Step-by-Step Solution: Aₙ = 5000 * (1 + 0.10)^5(1 + 0.10)^5 = 1.1^5 = 1.61051 (approx.)Aₙ ≈ 5000 * 1.61051 = 8052.55 vehicles/dayRounded to the nearest option → 8050 vehicles. Verification / Alternative check: Check successive compounding: Year 1: 5500; Year 2: 6050; Year 3: 6655; Year 4: 7321; Year 5: ≈ 8053. The result is consistent. Why Other Options Are Wrong: 6050, 7050, 9050: correspond roughly to years 2, between years 2–4, and above year 5 for 10% growth; they are not the 5-year value. Common Pitfalls: Applying linear growth instead of compound growth, which underestimates future volumes. Rounding too early and getting 8000 instead of ≈8050. Final Answer: 8050 vehicles.

Highway Engineering Questions