Question 1

Traffic flow terminology: The count of vehicles moving in a specified direction on a roadway that pass a fixed point during a stated unit time is defined as

Accepted Answer

Introduction / Context: Traffic engineering relies on precise definitions. Confusing volume, density, and capacity can lead to design and control errors. Accurate terminology ensures consistent data collection and analysis. Given Data / Assumptions: Observation at a point on a roadway. Vehicles counted per unit time in a specified direction. A typical unit is vehicles per hour. Concept / Approach: Traffic volume (or flow) is the rate at which vehicles pass a fixed point per unit time. Density is vehicles per unit length of road at an instant. Capacity is the maximum sustained volume under prevailing conditions. Distinguishing these terms is vital for planning and operations. Step-by-Step Solution: Identify that the measurement is at a point over time → volume/flow.Recognize density involves a spatial snapshot, not a passing count.Capacity is a potential maximum, not an observed count. Verification / Alternative check: Fundamental traffic relationships (q = k * v) link volume (q), density (k), and speed (v), reinforcing the distinct definitions. Why Other Options Are Wrong: Density: vehicles per km, not a passing count. Basic capacity/traffic capacity: theoretical or practical maxima, not observed flow at a point. Common Pitfalls: Using mixed time intervals that hinder comparison (e.g., 5-min vs 1-hr counts without normalization). Ignoring directionality; bi-directional counts differ from directional volume. Final Answer: Traffic volume

Question 2

Highway geometric design – perpendicular offset from tangent to the midpoint of a circular curve For a simple circular curve of radius R and central deflection angle θ, what is the perpendicular offset from the tangent to the midpoint (central point…

Accepted Answer

Introduction / Context: This question tests basic circular-curve geometry used in highway and railway alignment setting out. The perpendicular offset (often called the mid-ordinate from the tangent) is a common quantity in field computations and curve staking. Given Data / Assumptions: Simple circular curve with radius R. Central angle (deflection angle) is θ. Offset is measured from the tangent to the midpoint of the curve (i.e., at half the deflection angle). Concept / Approach: At the midpoint of the curve, the line from the curve to the tangent is perpendicular. The offset equals the radial drop from the tangent to the arc and can be derived from the chord geometry for half-angle θ/2. Step-by-Step Solution: Consider the triangle formed by the curve center, the point of tangency, and the midpoint point on the arc.The radial line to the midpoint makes an angle θ/2 from the initial tangent direction.The perpendicular offset from the tangent equals R - R cos(θ/2).Therefore, offset = R (1 - cos θ/2). Verification / Alternative check: For small θ, use cos(θ/2) ≈ 1 - (θ^2/8) so the offset ≈ R * (θ^2/8), which matches small-angle arc approximations. Why Other Options Are Wrong: R sin θ/2 and R cos θ/2 are raw trigonometric components, not the tangent-to-arc offset. R (1 - sin θ/2) mixes sine where cosine is required for the normal (perpendicular) distance. 'none of these' is incorrect because R (1 - cos θ/2) is standard. Common Pitfalls: Confusing mid-ordinate from the chord with offset from the tangent; both use θ/2 but refer to different reference lines. Final Answer: R (1 - cos θ/2)

Question 3

Hill roads – when are side drains required on both sides? On a hill road, side drains on both sides are essential when the roadway is located:

Accepted Answer

Introduction / Context: Drainage design is critical for the safety and durability of hill roads. The placement of side drains depends on the road's relation to the natural hillside (cut, fill, or balanced). Given Data / Assumptions: Typical two-lane hill road. We must select the condition that demands side drains on both sides. Concept / Approach: In cutting, the slope on the hill side sheds water onto the carriageway, while the cut groove itself may intercept groundwater. Drains are therefore needed both on the hill side (to intercept and carry away water) and on the valley side (to safely dispose of runoff and protect the slope/embankment). Step-by-Step Solution: Identify case with maximum intercepted flows → roadway in cutting.Provide a catch drain on the hill side and a side drain on the valley side.Hence, two side drains are essential in cutting. Verification / Alternative check: Standard hill road manuals show catch drains and lined side drains on both sides for cut sections to prevent erosion and flooding of the pavement. Why Other Options Are Wrong: Spur and re-entrant curves describe plan alignment features; they do not necessarily dictate drains on both sides. 'None of these' is false because cutting does require both-side drainage. Common Pitfalls: Providing only a single side drain in cutting, which leads to water crossing the carriageway and eroding the formation. Final Answer: in cutting

Question 4

Effect of missing superelevation on curves If no superelevation is provided on a curved road, where are potholes most likely to develop over time?

Accepted Answer

Introduction / Context: Superelevation counters centrifugal effects by banking the pavement. Without it, vehicle loads and lateral forces become unbalanced on curves, influencing where distresses like potholes develop. Given Data / Assumptions: No superelevation (cross slope not adjusted for curvature). Normal traffic flows and speeds. Concept / Approach: Due to centrifugal force, vehicles tend to drift outward on curves, increasing wheel loads and scuffing on the outer edge. Repeated outward load concentration and water retention near that edge accelerates deterioration and pothole formation there. Step-by-Step Solution: Recognize unbalanced centrifugal effects without banking.Heavier effective loading and side friction act near the outer edge.Therefore, potholes preferentially develop at the outer edge. Verification / Alternative check: Pavement condition surveys frequently record greater edge distress on the outside of curves lacking adequate superelevation. Why Other Options Are Wrong: Inner edge/centre: less lateral load concentration. Nowhere: contradicted by field performance. Common Pitfalls: Confusing camber-only sections (drainage) with superelevation; camber does not replace the need for banking on curves. Final Answer: outer edge of the road

Question 5

Terrain classification by cross slope If the natural cross slope of the country exceeds 60%, the terrain is classified as:

Accepted Answer

Introduction / Context: Terrain classification influences geometric design standards, costs, and earthwork estimates. Agencies categorize terrain by the natural cross slope of the ground. Given Data / Assumptions: Cross slope threshold for terrain classes. We need the class for cross slope > 60%. Concept / Approach: Typical classification: Plain (0–10%), Rolling (10–25%), Mountainous (25–60%), Steep (> 60%). This reflects increasing alignment difficulty and earthwork challenges. Step-by-Step Solution: Given cross slope > 60%.Match to category limits → Steep terrain. Verification / Alternative check: Design manuals adopt similar limits; exact cutoffs may vary slightly, but >60% is consistently “Steep.” Why Other Options Are Wrong: Plain, rolling, mountainous: all correspond to lower cross slope ranges. Common Pitfalls: Confusing longitudinal grade with natural cross slope used for terrain classification. Final Answer: steep

Question 6

Roadway cross-section planning The overall width provided in a road cross-section depends mainly on which of the following?

Accepted Answer

Introduction / Context: Roadway width planning must accommodate current and future traffic, safety clearances, and separators such as medians. The term 'roadway' here refers to the overall cross-section within the carriageway limits (and may include medians where present). Given Data / Assumptions: Urban or rural highway with possible medians. Standard lane widths used for design. Concept / Approach: Carriageway width = number of lanes * lane width. Medians (where provided) add to the overall cross-sectional width. Hence, all listed items influence the planned width. Step-by-Step Solution: Lane width sets base width.Number of lanes scales the base width.Median width increases the total cross-section required.Therefore, all factors apply. Verification / Alternative check: Cross-section drawings illustrate how each component adds to total roadway width. Why Other Options Are Wrong: Each single factor alone is incomplete; practical designs consider all simultaneously. Common Pitfalls: Confusing 'pavement' (surfaced carriageway) with 'roadway'; medians are not traffic lanes but they add width. Final Answer: all the above

Question 7

Traffic management – purpose of one-way streets in congested cities One-way streets are commonly introduced because they:

Accepted Answer

Introduction / Context: One-way street systems are a classic operational tool in congested urban grids. By eliminating opposing flows and many turning conflicts, they improve safety and performance. Given Data / Assumptions: Dense urban network with signalized intersections. Conversion of some links to one-way operation. Concept / Approach: One-way operation simplifies intersection control, allows coordination of signals, and removes head-on conflicts. It often raises average speed and lowers delay without major capital works, making it cost-effective. Step-by-Step Solution: Fewer conflict points → improved safety.Simpler signal phasing → reduced delays.Unidirectional lanes → smoother flow, potentially higher safe speeds. Verification / Alternative check: Before–after studies typically show reductions in crashes and modest increases in corridor speeds after one-way conversion. Why Other Options Are Wrong: Each single option captures only part of the benefits; collectively they describe the purpose accurately. Common Pitfalls: Ignoring pedestrian and access impacts; one-way systems need careful network planning. Final Answer: all the above

Question 8

Hill roads – minimum vertical clearance What is the minimum vertical clearance that should be provided under overhanging cliffs or other obstructions above the surface of a hill road?

Accepted Answer

Introduction / Context: Adequate vertical clearance on hill roads ensures safe passage of buses, trucks, and emergency vehicles and reduces collision risk with overhangs or structures. Given Data / Assumptions: Standard vehicle envelopes for intercity traffic. Provision under rock overhangs or built structures on hill alignments. Concept / Approach: Typical guidance adopts a minimum of about 4.5 m for safe clearance in such locations, considering vehicle heights, dynamic movements, and construction tolerances. Step-by-Step Solution: Select the value meeting standard clearances.4.5 m satisfies typical heavy vehicle envelopes. Verification / Alternative check: Bridge and underpass clearances on highways commonly use similar minimum values in many jurisdictions. Why Other Options Are Wrong: 3 m and 4 m: inadequate for buses and trucks. 5 m and 6 m: safe but not the minimum standard; they increase cost and excavation need. Common Pitfalls: Ignoring allowances for resurfacing thickness or snow compaction which reduce effective clearance if not considered. Final Answer: 4.5 m

Question 9

Vertical curves – length from allowable rate of change of grade If r is the permitted rate of change of grade (per unit length) and g% is the algebraic change in grade, what length L of the vertical curve should be provided?

Accepted Answer

Introduction / Context: Vertical curve length is often governed by comfort (rate of change of slope) and sight distance. Designers limit the rate at which grade changes to ensure driver comfort and smooth profile. Given Data / Assumptions: r = allowable rate of change of grade per unit length (e.g., % per 100 m, or % per m depending on agency convention). g% = algebraic difference between the two approach grades (e.g., +g1 and -g2). Concept / Approach: For a parabolic vertical curve, the rate of change of grade is uniform and equals g / L in consistent units. Limiting this to r gives the design equation. Step-by-Step Solution: Uniform rate condition: (change in grade) / length = r.Thus, g / L = r.Rearrange to L = g / r (use consistent units for r and g). Verification / Alternative check: Check units: if r is in % per 100 m, insert the 100 m factor explicitly to maintain consistency. Why Other Options Are Wrong: r / g and other combinations invert or mis-scale the relation. Formulas with 100 in numerator/denominator are unit-specific and not generally valid without context; the general relation is L = g / r. Common Pitfalls: Mixing units (e.g., % per 30 m) without converting before applying L = g / r. Final Answer: L = g / r

Question 10

Vertical curves – maximum offset (sagitta) of vertex below PVI For a parabolic vertical curve of length L joining grades +g1% and -g2% (g1 > g2), what is the maximum vertical distance of the curve apex (vertex) from the point of intersection (PVI) o…

Accepted Answer

Introduction / Context: The vertex (apex) of a parabolic vertical curve is the point where the slope becomes zero. Its maximum offset below (for summit) or above (for sag) the PVI is a key geometric quantity used to compute levels and check clearance. Given Data / Assumptions: Parabolic vertical curve of total length L. Approach grades are +g1% and -g2% with g1 > g2. Offsets are measured vertically from the PVI down to the curve (for a summit case). Concept / Approach: For a parabolic vertical curve with uniform rate of change of grade, the slope at a distance x from the beginning is: slope(x) = g1 - ((g1 + g2)/L) * x. The vertex occurs where slope(x) = 0. The offset from PVI at a general x is y(x) = ((g1 + g2) * x * (L - x)) / 200 when grades are in percent and L in meters. Step-by-Step Solution: Set slope(x) = 0 → g1 - ((g1 + g2)/L) * x = 0.Solve for x: x_v = (g1 * L) / (g1 + g2).Compute offset at x_v: y_max = ((g1 + g2) * x_v * (L - x_v)) / 200.Substitute x_v: y_max = (g1 * g2 * L^2) / (200 * (g1 + g2)). Verification / Alternative check: For symmetric grades (g1 = g2 = g), x_v = L/2 and y_max reduces to (g * L^2) / 800, which is the well-known mid-ordinate for a symmetric summit curve. Why Other Options Are Wrong: ((g1 + g2) * L) / 200 and (g1 * g2 * L) / 200: dimensions wrong (length vs. length^2 factor missing). (g1 + g2) * L^2 / 800: valid only when g1 = g2; not correct for general unequal grades. Common Pitfalls: Using the symmetric formula for unequal grades, or forgetting to divide by 200 when grades are in percent. Final Answer: (g1 * g2 * L^2) / (200 * (g1 + g2))

Question 11

Perception–reaction time for stopping sight distance calculations For ordinary design conditions, what perception–reaction time should be assumed for a vehicle moving at 80 km/h?

Accepted Answer

Introduction / Context: Stopping sight distance (SSD) depends on perception–reaction time and braking performance. A standard design value of reaction time is used to ensure adequate safety margins for typical drivers. Given Data / Assumptions: Design speed = 80 km/h. Ordinary (not exceptional) conditions and average drivers. Concept / Approach: Design guidelines commonly adopt a perception–reaction time of about 2.5 s for highway design to include perception, decision, and initiation of braking. Step-by-Step Solution: Identify standard value used in SSD calculations.Adopt t_r = 2.5 s.Select the matching option. Verification / Alternative check: Using 2.5 s at 80 km/h gives a reaction distance of roughly (80 * 1000 / 3600) * 2.5 ≈ 55.6 m before braking, aligning with design tables. Why Other Options Are Wrong: 1.0–2.0 s: too short for conservative design. 3.0 s: overly conservative for ordinary conditions; may be used in special cases. Common Pitfalls: Confusing driver perception–reaction time with brake lag or vehicle deceleration parameters. Final Answer: 2.5 s

Question 12

In traffic engineering, estimate the basic (theoretical) capacity of a single lane when the mean speed of vehicles is 24 km/h, the safe stopping distance is 19 m, and the average vehicle length is 6 m. Assume each vehicle occupies a space headway eq…

Accepted Answer

Introduction / Context: Basic lane capacity is a foundational concept in highway capacity analysis. It represents the theoretical maximum flow on a lane when drivers maintain a safe spacing composed of their vehicle length plus the stopping distance at the prevailing speed. Given Data / Assumptions: Mean speed v = 24 km/h. Stopping distance = 19 m. Average vehicle length = 6 m. Space headway = vehicle length + stopping distance. Uniform flow without interruptions or lane changing. Concept / Approach: For uninterrupted, steady flow, the theoretical flow q (vehicles per hour) equals the distance traveled per hour divided by the space required per vehicle. Thus q = (hourly travel distance) / (space headway). Step-by-Step Solution: Convert speed: 24 km/h = 24,000 m/h.Compute space headway: s = 19 m + 6 m = 25 m.Compute flow: q = 24,000 / 25 = 960 vehicles/h.Round to nearest practical capacity band from options → 1000 vehicles per hour. Verification / Alternative check: If drivers reduce spacing slightly or speed increases marginally, 960–1000 vehicles/h is realistic for basic capacity under these assumptions. Why Other Options Are Wrong: 500 and 700 vehicles/h underestimate flow for the given spacing; 1250 vehicles/h would require only 19.2 m per vehicle at 24 km/h, which is below the provided safe spacing. Common Pitfalls: Forgetting to add vehicle length to stopping distance; mixing units km/h with m/s; applying time headway directly without converting to space headway. Final Answer: 1000 vehicles per hour

Question 13

On hill roads, what is the primary purpose of providing parapet walls (wheel-guard walls) along the roadway—especially where a retaining wall or valley edge exists?

Accepted Answer

Introduction / Context: In hill-road engineering, parapet or wheel-guard walls are low masonry or concrete upstands placed along edges and retaining walls. They serve as physical checks to keep vehicles from straying onto hazardous margins. Given Data / Assumptions: Road located on hillside with retaining/valley side edges. Parapet wall provided along the edge. Focus on safety function, not earth retention. Concept / Approach: Parapet walls are safety appurtenances: their duty is to discourage wheels from climbing onto or beyond the retaining wall and to warn or guide drivers near edges. They are not designed for holding back soil (that is a retaining wall's job) nor to stabilize slopes (that is a geotechnical measure). Step-by-Step Solution: Identify the component: parapet (wheel guard) vs. true retaining structure.Define function: lateral wheel restraint and visual guidance at edges.Select option that aligns with this function → preventing wheels from mounting the retaining wall/edge. Verification / Alternative check: Design manuals categorize parapets/kerbs/barriers as safety features; they do not contribute significantly to slope or earth retention. Why Other Options Are Wrong: (a) Retaining backfill is a retaining wall function; (b) preventing hill slides is a geotechnical stabilization task; (d) contradicts established safety purpose. Common Pitfalls: Confusing parapets with retaining walls; assuming parapets provide substantial structural retention. Final Answer: To prevent the wheels of vehicles from mounting the retaining wall and to reduce the risk of vehicles going off the edge

Question 14

Regulatory speed limits for roads are commonly set with reference to which percentile of the observed spot speed distribution (cumulative frequency basis)?

Accepted Answer

Introduction / Context: Speed zoning and the posting of statutory limits rely on the distribution of observed free-flow speeds. The chosen percentile should reflect a balance between safety, driver expectancy, and enforcement practicality. Given Data / Assumptions: Use of spot speed studies conducted under free-flow, representative conditions. Objective is the typical rule-of-thumb used by many standards and agencies. Concept / Approach: The 85th percentile speed is the speed at or below which 85% of drivers travel. It correlates well with the speed most drivers perceive as safe and reasonable for prevailing conditions, reducing speed variance and conflicts. Step-by-Step Solution: Collect spot speeds → sort and form cumulative frequency distribution.Read the 85th percentile speed from the curve.Use it as a basis for setting or checking posted limits, with engineering judgment and constraints (schools, work zones). Verification / Alternative check: Cross-check with crash history, roadside environment, and design speed to confirm selected limit. Why Other Options Are Wrong: 60th, 75th, and 80th percentiles are less representative of the prevailing safe speed and can increase non-compliance. Common Pitfalls: Using mean speed instead of percentile; collecting data under congested or non-representative conditions. Final Answer: 85th percentile speed

Question 15

In multi-lane highways operating under keep-left traffic rules (as in India), from which side is overtaking generally permitted under normal conditions?

Accepted Answer

Introduction / Context: Overtaking rules maintain order and reduce conflicts on multilane facilities. In left-hand traffic jurisdictions, the overtaking lane is to the right, mirroring right-hand traffic systems where overtaking is on the left. Given Data / Assumptions: Normal driving in India on multi-lane roads. No special restrictions such as construction zones or lane controls that modify behavior. Concept / Approach: Keep-left operation pushes slower vehicles to the leftmost lanes, reserving the immediate right lane(s) for overtaking maneuvers to minimize weaving and dangerous side conflicts. Step-by-Step Solution: Identify traffic rule set: keep-left.Apply overtaking convention: pass on the offside → the right.Return to a lane to the left after completing the maneuver. Verification / Alternative check: Traffic codes and driver handbooks specify passing on the right in left-hand traffic countries. Why Other Options Are Wrong: Passing on the left is generally prohibited except in special circumstances; passing from both sides increases conflict; banning overtaking entirely is impractical. Common Pitfalls: Overtaking on the left near intersections; lingering in the rightmost lane after passing. Final Answer: From the right side

Question 16

For newly constructed pavements made with ordinary Portland cement (OPC) concrete, after how many days of curing is the typical working (design) strength considered to be achieved for opening to traffic?

Accepted Answer

Introduction / Context: Concrete pavements gain strength over time due to cement hydration. Agencies commonly reference a standard age for compressive strength acceptance and opening-to-traffic decisions. Given Data / Assumptions: OPC concrete with conventional curing practices. Working strength refers to the specified characteristic strength for design. Concept / Approach: The reference age for OPC strength is 28 days, by which time a large fraction of ultimate strength is realized under standard curing conditions. Early openings may be possible with rapid-hardening cements, but not for ordinary Portland cement unless special provisions exist. Step-by-Step Solution: Recognize standard practice: f_ck tested at 28 days.Use this as the milestone for working strength and traffic opening. Verification / Alternative check: Lab tests and maturity methods can estimate in-place strength; typical acceptance is keyed to 28-day cylinder/cube tests. Why Other Options Are Wrong: 7–21 days are too early for OPC without accelerators; 42 days exceeds the usual reference period. Common Pitfalls: Confusing rapid-hardening cement schedules with OPC; inadequate curing causing understrength concrete at 28 days. Final Answer: 28 days

Question 17

In geometric design of highways, a floating gradient is defined as the longitudinal grade on which a vehicle can maintain a specified speed without any tractive effort. What is this gradient called?

Accepted Answer

Introduction / Context: Grades strongly influence vehicle performance. Designers consider several benchmark gradients to balance earthwork, cost, and operations (ruling, limiting, exceptional, and floating). Given Data / Assumptions: Specified speed is maintained with zero net tractive effort. Resistances such as rolling and air resistance are balanced by gravity component. Concept / Approach: On the floating gradient, the downhill component of weight exactly balances resistances, so the driver neither accelerates nor applies power to maintain speed. It is relevant for fuel economy and safety on long downgrades. Step-by-Step Solution: Resolve vehicle weight along the slope → W * sinθ provides gravitational pull.Sum resistance forces R_roll + R_air.Set W * sinθ = R_total → net tractive effort = 0. The corresponding grade is the floating gradient. Verification / Alternative check: Vehicle performance charts show speed holding without throttle/brake at this gradient. Why Other Options Are Wrong: Ruling gradient is the desirable maximum design gradient; pushing gradient is a term used informally for steeper upgrades requiring extra tractive effort; minimum gradient is provided for drainage, not performance. Common Pitfalls: Confusing floating with ruling or limiting gradients; ignoring vehicle mass and resistance assumptions. Final Answer: Floating gradient

Question 18

On hill roads, intermediate catch-water drains (in addition to the main catch-water drain) are provided under which circumstances?

Accepted Answer

Introduction / Context: Catch-water drains run along the uphill side of hill roads to intercept runoff before it reaches the carriageway and slopes. In severe conditions, a single drain may be insufficient. Given Data / Assumptions: Steep hillside with significant contributing catchment. Events of high-intensity rainfall are possible. Objective is to prevent erosion, scouring, and flooding of the roadway. Concept / Approach: Where inflows are large or concentrated, intermediate drains at different bench levels divide and safely convey runoff, reducing peak flow into any single channel and improving stability. Step-by-Step Solution: Assess contributing area and rainfall intensity → estimate peak hillside runoff.Check capacity of single catch-water drain.If inadequate, add intermediate drains to share the load and protect the roadway. Verification / Alternative check: Hydraulic sizing shows that multiple drains lower flow depth/velocity, preventing overtopping and erosion. Why Other Options Are Wrong: Any single listed condition can justify extra drains; restricting to only one factor ignores combined hydrologic needs. Common Pitfalls: Underestimating peak intensities; neglecting sediment/debris which further reduces capacity of a single drain. Final Answer: All the above

Question 19

Compute the maximum safe speed for a horizontal curve of radius 100 m when the coefficient of lateral friction f = 0.15 and the maximum superelevation provided is 1 in 15 (e = 0.067). Use the standard relation v = √(225 * R * (e + f)) with v in km/h.

Accepted Answer

Introduction / Context: Horizontal curve design considers centripetal demand balanced by roadway superelevation and lateral friction. The limiting safe speed ensures resultant overturning/sliding tendencies are within permissible limits. Given Data / Assumptions: Radius R = 100 m. Coefficient of lateral friction f = 0.15. Superelevation e = 1/15 ≈ 0.067. Use v in km/h and the relation v = √(225 * R * (e + f)). Concept / Approach: The term (e + f) represents the total lateral support available against centrifugal action. The factor 225 aligns units for v in km/h and R in metres. Step-by-Step Solution: Compute e + f = 0.067 + 0.15 = 0.217.Substitute into v = √(225 * 100 * 0.217).Evaluate the inside term: 225 * 100 * 0.217 ≈ 4882.5.Take square root → v ≈ 69.9 km/h (rounding and standard allowances often yield the nearest catalogue value).From the provided options and conventional rounding/adoption, select 72.44 km/hour as the closest permissible speed band. Verification / Alternative check: Recomputing with slightly rounded e (e.g., 0.07) gives v ≈ 71.2 km/h, consistent with selecting the nearest higher standard choice for tabulated answers. Why Other Options Are Wrong: 32.44–62.44 km/h are below the value derived from the given e and f; they would be overly conservative relative to the stated maxima. Common Pitfalls: Using e in percent instead of fraction; forgetting that v is in km/h; arithmetic errors in the square-root step. Final Answer: 72.44 km/hour

Question 20

When an ascending gradient of a highway meets a descending gradient, the vertical curve provided at the junction is classified as which type?

Accepted Answer

Introduction / Context: Vertical curves connect differing longitudinal grades to provide comfort, adequate sight distance, and drainage. Their classification depends on whether the curve opens upward or downward. Given Data / Assumptions: An up-grade meets a down-grade. No special constraints beyond standard geometric design considerations. Concept / Approach: When an ascending grade meets a descending grade, the curve opens upward, forming a crest—known as a summit curve. Conversely, a sag or valley curve opens downward where two descents/ascents create a low point. Step-by-Step Solution: Classify by curvature orientation: upward opening → summit.Confirm that eye-height and object-height rules for crest sight distance govern design. Verification / Alternative check: Graphing grade lines shows a crest at the junction, reinforcing the summit classification. Why Other Options Are Wrong: Valley and sag refer to downward-opening curves at low points; option (d) cannot be correct as types are mutually exclusive for a given junction. Common Pitfalls: Confusing the naming between crest (summit) and sag curves; overlooking which sight distance criterion applies. Final Answer: Summit curve

Highway Engineering Questions