Transportation Engineering- II (CE-502) - Unit 1 Short Notes

UNIT 1: HIGHWAY GEOMETRIC DESIGN & ALIGNMENT

1.1 Road Alignment & Surveys

• Map Study: Preliminary reconnaissance using topographical maps to identify feasible corridors.

• Engineering Surveys: Conducted for final alignment selection.

  • Reconnaissance Survey: Ground inspection of short-listed routes.

  • Preliminary Survey: Detailed topographical survey (contours, drainage, structures).

  • Detailed Survey: Final location survey (centerline, cross-sections, soil investigation).

[!TIP] Exam Focus: Differentiate between the three survey stages. Map study is the first step, not a substitute for ground surveys.

1.2 Horizontal Curves

Necessity: Provide smooth transition between straight sections, change direction gradually, reduce centrifugal force impact.

Types & Key Features:

Fundamental Elements of a Simple Circular Curve:

• Radius (R)

• Deflection Angle (Δ)

• Tangent Length (T): $$\displaystyle T = R \tan(\Delta/2) $$

• Length of Curve (Lc): $$\displaystyle L_c = \frac{\pi R \Delta}{180} $$ (in degrees) or $$\displaystyle L_c = R \Delta $$ (in radians)

• Chord Length (C): $$\displaystyle C = 2R \sin(\Delta/2) $$

• Apex Distance (M): $$\displaystyle M = R \left( \frac{1}{\cos(\Delta/2)} - 1 \right) $$

Design of Superelevation (e): Purpose: Counteract centrifugal force on curves. Derivation: Equilibrium of forces: $$\displaystyle e + f = \frac{V^2}{gR} $$

Where, $f$ = side friction factor, $V$ = design speed (m/s), $g$ = gravity. IRC Recommendation (IRC 73-2015):

• Max $$\displaystyle e = 7\% $$ for plain/rolling terrain, $10\%$ for hilly terrain.

• Max $$\displaystyle f = 0.7 $$ (for $V$ up to 50 kmph) to $0.5$ (for $V$ > 100 kmph).

• Design Formula: $$\displaystyle e + f = \frac{V^2}{127R} $$ ($V$ in kmph, $R$ in m).

• Superelevation for mixed traffic: Based on 75% of design speed.

[!TIP] Superelevation is designed for the design speed, not the posted speed. Remember the formula with 127 constant.

1.3 Sight Distance

Stopping Sight Distance (SSD): Distance needed to see an object and stop safely.

$$SSD = 0.278 V t + \frac{V^2}{254(f \pm G)}$$

Where, $V$ = speed (kmph), $t$ = brake reaction time (2.5 sec), $f$ = friction coefficient, $G$ = gradient (+ for upgrade, - for downgrade).

Overtaking Sight Distance (OSD): Distance required for a safe overtaking maneuver. For Two-Way Traffic (IRC):

$$OSD = d_1 + d_2 + d_3$$

• $$\displaystyle d_1 $$ = Distance travelled during reaction time (Overtaking vehicle).

  $$\displaystyle d_1 = 0.278 V_b t $$

• $$\displaystyle d_2 $$ = Distance travelled while overtaking (into opposing lane).

  $$\displaystyle d_2 = 0.278 V_b T $$ (where $$\displaystyle T = \sqrt{\frac{4d}{s}} $$)

• $$\displaystyle d_3 $$ = Distance travelled by opposing vehicle during overtaking.

  $$\displaystyle d_3 = 0.278 V_m T $$

Where, $$\displaystyle V_b $$ = speed of overtaking vehicle (kmph), $$\displaystyle V_m $$ = speed of overtaken vehicle (kmph), $d$ = clear distance between vehicles (0.6m min), $s$ = spacing during overtaking (1.5-2.0m).

For One-Way Traffic: $$\displaystyle d_3 $$ term is omitted.

Intermediate Sight Distance (ISD): $$\displaystyle ISD = 2 \times SSD $$

Factors Affecting SSD: Vehicle speed, driver reaction time, brake efficiency, road gradient, tire-road friction.

[!TIP] OSD is always greater than SSD. For numericals, first calculate $T$ (overtaking time), then $$\displaystyle d_2 $$, $$\displaystyle d_3 $$.

1.4 Vertical Curves

Summit Curve (Convex): Critical for SSD (headlight sight distance). Parabolic shape preferred. Length (L) for given SSD:

• For $L \geq SSD$: $$\displaystyle L = \frac{NS^2}{(\sqrt{h_1} + \sqrt{h_2})^2} $$

• For $$\displaystyle L < SSD $$: $$\displaystyle L = 2S - \frac{(\sqrt{h_1} + \sqrt{h_2})^2}{N} $$

Where, $N$ = deviation angle ($$\displaystyle |n_2 - n_1| $$), $$\displaystyle h_1 $$ = driver eye height (1.2m), $$\displaystyle h_2 $$ = object height (0.15m), $S$ = SSD.

Sag Curve (Concave): Critical for headlight beam at night and passenger comfort. Same formulas apply with different $$\displaystyle h_1, h_2 $$ values for headlight sight distance.

1.5 Cross-Sectional Elements

1.6 Special Topics

Overtaking Zones:

• Minimum Length: $$\displaystyle L_{min} = 3 \times OSD $$ (for two-way traffic).

• Desirable Length: $5 \times OSD$.

• Signs: "Overtaking Zone Ahead" (start), "Overtaking Prohibited" (end).

Off-tracking:

• Definition: Rear wheels follow a shorter path than front wheels (stub turning).

• Calculation (for mean radius $$\displaystyle R_m $$): $$\displaystyle Off\text{-}tracking = \sqrt{R_m^2 + l^2} - R_m \approx \frac{l^2}{2R_m} $$

Where, $l$ = wheelbase.

Grade Separated Intersections:

• Definition: Intersections at different levels (flyover/underpass).

• Advantages: No crossing conflict, high capacity & speed.

• Limitations: High cost, large land, long grades for climbing vehicles.

UNIT 2: PAVEMENT DESIGN & MATERIALS

2.1 Pavement Types & Comparison

2.2 Flexible Pavement Design (CBR Method - IRC:37-2018)

California Bearing Ratio (CBR):

• Test: Penetration of a piston (50mm dia) into a soaked soil sample (after 96hrs soaking).

• CBR Value (%): $$\displaystyle \frac{Load \ at \ 2.5mm \ (or \ 5.0mm) \ penetration}{Standard \ load \ at \ same \ penetration} \times 100 $$

• Significance: Measure of soil strength. Higher CBR → thinner pavement.

• Typical Values: Clay (2-5%), Silt (5-15%), Sand (15-30%), Gravel (40-100%).

Design Procedure (IRC):

1. Determine Design Traffic (cumulative standard axles, ESA, in msa).

2. Obtain CBR value of subgrade soil (soaked).

3. Use IRC:37 design charts/graphs (or equation) relating traffic (msa), CBR, and total pavement thickness.

4. Layer Thickness Allocation: Based on layer coefficients (a-values) or equal layer strength criteria.

   • Subgrade: CBR-based.

   • Sub-base (Graded aggregates): 150-225mm.

   • Base (WBM/WMM): 250-300mm.

   • Surfacing (BC/DBM): 50-100mm.

5. Sketch: Show cross-section with all layer thicknesses.

[!TIP] CBR is for SOAKED conditions. Design traffic is in msa (million standard axles of 8.16 t).

2.3 Rigid Pavement Design (IRC:58-2002)

Design Parameters:

• Design Flexural Strength (σ_f): 4.5-5.0 MPa for普通水泥.

• Modulus of Elasticity (E_c): 3.0×10⁴ MPa.

• Poisson's Ratio (μ): 0.15.

• Modulus of Subgrade Reaction (k): 0.085-0.150 N/mm³ (from plate load test).

Stresses Considered:

1. Load Stress (σ_l): Due to wheel load (using Westergaard's equations).

2. Warping Stress (σ_w): Due to temperature differential (top vs bottom).

3. Frictional Stress (σ_f): Due to friction with subgrade (often negligible for slabs > 10m).

Computation of Slab Thickness:

• Find critical combination of stresses (e.g., load + warping).

• Ensure Total Stress ≤ Design Flexural Strength with appropriate factor of safety.

• Use IRC:58 charts/graphs relating corner stress, slab length, k-value, and required thickness.

2.4 Pavement Materials & Construction

Water Bound Macadam (WBM):

• Materials: Coarse aggregates (hard, durable, 90-40mm), screenings (filler), binding material (practically nil, just water).

• Construction: 1) Sub-grade prep, 2) Spreading coarse aggregates in layers, 3) Rolling with 8-10t roller, 4) Apply screenings, 5) Final rolling, 6) Sprinkling & rolling, 7) Curing.

• Uses: Base course for flexible pavements, WBM roads (low traffic).

• Limitations: Dusty, requires good aggregates, not waterproof.

Bituminous Construction:

• Bituminous Macadam (BM): 40mm nominal size, for base course. Dense Bituminous Macadam (DBM): 19-25mm, for binder course.

• Bituminous Concrete (BC): 13.2-19mm nominal, for wearing course.

  • IRC Specs: Aggregate gradation (dense), bitumen content (5-6%), Marshall stability (>900 kg), voids (3-5%).

• Tack Coat: Thin bitumen film (0.2-0.5 kg/m²) for bonding layers.

• Seal Coat: Thin bituminous layer (1.0-1.5 kg/m²) on top for waterproofing and texture.

Wet Mix Macadam (WMM):

• Similar to WBM but uses moist (not soaked) aggregates and no screenings during rolling. Better interlock, less dust. Used as base/sub-base.

2.5 Soil Stabilization

Mechanical Stabilization:

• Method: Blending poor soil with coarse aggregates (gravel) or fine aggregates (sand) to achieve desired gradation and strength.

• Purpose: Improve gradation, reduce plasticity, increase bearing capacity, reduce swelling.

• Suitability: Granular soils with excess fines or clayey soils with excess clay.

Scope in Road Construction:

• Subgrade improvement.

• Base/subbase construction in low-cost roads.

• Embankment filling with locally available materials.

Other Brief Methods:

• Cement Stabilization: For granular/cohesive soils (5-10% cement).

• Lime Stabilization: For clayey soils (3-6% lime).

• Bitumen Stabilization: For base courses (2-4% bitumen).

UNIT 3: TRAFFIC ENGINEERING & SAFETY

3.1 Traffic Studies & Analysis

Origin-Destination (O&D) Study:

• Purpose: Determine trip origins, destinations, purposes, routes.

• Methods: Home Interview, Roadside Interview, Postcard, Registration Number (for cordon lines).

• Uses: Trip generation/distribution modelling, planning new roads/transit, traffic management.

Speed Studies:

• Spot Speed: Speed at a specific point.

• Running Speed: Average speed while moving (excluding stops).

• Time-Mean Speed: Arithmetic mean of spot speeds.

• Space-Mean Speed: Harmonic mean of spot speeds (more accurate for flow).

• Average Travel Speed: Total distance / total time (including stops).

• Methods: Enoscope (visual), Radar Gun, Pneumatic Tubes (record individual axle times).

Parking Studies:

• Purpose: Determine parking demand, turnover, duration.

• On-Street Parking Types:

  • Parallel: 2.5-3.0m width, least disruptive but uses most curb length.

  • Angle (30°-60°): Easier parking, less width.

  • Perpendicular (90°): Most efficient use of space, but requires more width.

3.2 Traffic Control Devices

Traffic Markings (IRC:67):

Road Lighting Design Factors:

• Illumination Level (Lux): Depends on road type & traffic.

• Uniformity Ratio: Min/Max or Average/Min illumination.

• Glare Control: Luminaire design, mounting height.

• Mounting Height & Spacing: Based on luminaire type and road width.

3.3 Traffic Flow & Distribution

Trip Distribution (4-Step Model):

• Part of transportation planning after trip generation.

• Allocates trips from production zones to attraction zones.

• Methods: Growth Factor, Gravity Model (most common), Opportunity Model.

Wind Rose Diagram:

• Explanation: Circular graph showing wind speed/frequency distribution by direction.

• Types: Speed Wind Rose, Direction Wind Rose, Resultant Wind Rose.

• Applications:

  • Airports: Runway alignment (prevailing wind direction for takeoff/landing).

  • Roads: Pollution dispersion, design of cross-sections (crosswind effects).

UNIT 4: AIRPORT ENGINEERING

4.1 Airport Planning & Site Selection

Factors:

• Topography: Relatively flat, adequate area for expansion.

• Wind: Prevailing wind direction along runway (crosswind component < 15-20 kmph).

• Obstructions: Clear approach areas (no tall buildings/trees).

• Accessibility: Road/rail connectivity to city.

• Environment: Noise pollution, ecological sensitivity.

• Future Expansion: Land availability.

Zoning Regulations (ICAO Annex 14):

• Approach Surface: Sloping surface from runway end outward (inner width = runway width, slope 1:50 to 1:75).

• Transitional Surface: Sloping from approach surface/runway edges outward (slope 1:2).

• Horizontal Surface: Horizontal surface at 45m above aerodrome elevation (for tall obstacles).

• Conical Surface: Sloping surface from outer edge of horizontal surface outward (slope 1:20).

DiagramSEARCH: ICAO airport zoning surfaces diagram

4.2 Aircraft Characteristics & Airport Design

Key Characteristics:

1. Wingspan (WS): Determines taxiway & apron width.

2. Tail Height (TH): Determines clearance under structures.

3. Wheel Base (WB): Determines turning radius & taxiway curvature.

4. Turning Radius: Minimum radius for taxiing (depends on WB & steering angle).

5. Approach Speed (V_app): Determines runway length & ILS category.

6. Cockpit Eye Height (CEH): Determines obstacle clearance during approach.

7. Landing Gear Geometry: Outrigger gear width affects taxiway width.

Effect on Design:

• Runway Orientation: Based on wind direction & V_app.

• Taxiway Design: Width = 0.6×WS, curvature radius ≥ 1.2×WB.

• Obstacle Clearance: Approach surface slope based on CEH.

DiagramCANVAS: Sketch of typical commercial aircraft (e.g., A320) showing WS, TH, WB, CEH, landing gear layout

4.3 Runway Design

Geometrical Elements:

• Length: Based on aircraft performance & airport elevation.

• Width: 45m (Code 4C), 60m (Code 4E) per ICAO.

• Orientation: Wind direction (crosswind < 15 kmph).

• Gradient: Max 1% (preferably 0.5%), up/down gradient ≤ 0.8%.

• Safety Areas: RESA (Runway End Safety Area) - 90m x 300m beyond runway end.

Runway Length Correction: Corrected Length (L) = L₀ + ΔL_elev + ΔL_temp + ΔL_grad

Where, $$\displaystyle L_0 $$ = Standard length (under MSL, 15°C, zero grad, no wind).

1. Elevation Correction: $$\displaystyle \Delta L_{elev} = L_0 \times \frac{elevation}{300} $$ (approx. rule of thumb) or use ICAO formula.

2. Temperature Correction: $$\displaystyle \Delta L_{temp} = L_0 \times \frac{(T_{ref} - 15)}{300} $$ (where $$\displaystyle T_{ref} $$ = monthly mean of max daily temp of hottest month).

3. Gradient Correction: $$\displaystyle \Delta L_{grad} = L_0 \times \frac{G}{100} $$ (G = effective gradient %).

[!TIP] All corrections are additive. Reference temperature is NOT daily max, but monthly mean of daily max.

4.4 Airport Lighting & Aids

Runway Lighting:

• Threshold Lights: Green (approach end), Red (far end).

• Edge Lights: White (runway), Yellow (last 600m).

• Centerline Lights: White (inner), Red (last 900m).

• Touchdown Zone Lights (TDZL): White, in 3 rows, 900m long.

• Approach Lighting System (ALS): Series of lights/barrettes extending 900m beyond threshold.

DiagramSEARCH: runway lighting system diagram ALS TDZL

Visual Aids:

• Rotating Beacon: Flashes white/green (airport identification) & white/yellow (military).

• Taxiway Lighting: Blue edge lights, green centerline lights.

Instrument Landing System (ILS):

• Localizer: Provides lateral guidance (course line).

• Glide Path: Provides vertical guidance (glide slope ~ 3°).

• Marker Beacons: Outer (400m from threshold), Middle (1000m), Inner (75m from threshold) - provide position.

• DME (Distance Measuring Equipment): Provides slant-range distance.

Precision Approach Radar (PAR):

• Provides both azimuth & elevation guidance to pilot via radar.

• Used as backup or at non-ILS airports.

4.5 Airport Classification & Other Facilities

Classification (ICAO): Based on Reference Field Length (RFL).

• Code Number (1-4): RFL (e.g., Code 4: RFL ≥ 1800m).

• Code Letter (A-F): Wingspan + Outer Main Gear Wheel Span (e.g., Code 4E: WS 52-65m, OMGS 9-14m).

Other Elements:

• Taxiway: Path for aircraft movement (design speed 30-50 kmph).

• Apron: Area for parking, loading/unloading.

• Terminal Building: Passenger & cargo processing.

• Airport Capacity: Max number of aircraft movements (arrivals+departures) per hour. Affected by: runway config, separation minima, ATC efficiency, weather.

UNIT 5: INSTITUTIONS, DEFINITIONS & SHORT NOTES

5.1 Indian Road & Research Organizations

• Central Road Research Institute (CRRI): Premier research institute (New Delhi) for road transport, traffic, pavement materials.

• Central Road Fund (CRF): Fund ( cess on petrol/diesel) for development & maintenance of state & national highways.

• Highway Research Board (HRB): Apex body under Ministry of Road Transport & Highways for coordinating research.

• Indian Road Congress (IRC): Apex professional body (est. 1934) that formulates codes & standards (e.g., IRC:37, IRC:58).

5.2 Key Definitions & Concepts

Joints in Rigid Pavement:

• Expansion Joint: Allows slab expansion due to temp rise. Filled with pre-moulded filler, topped with joint sealant.

• Contraction Joint: Controls cracking due to contraction (dowel bars for load transfer).

• Construction Joint: Where concreting stopped (tie bars for longitudinal, dowel for transverse).

• Longitudinal Joint: Between two lanes (tie bars to hold slabs together).

DiagramCANVAS: Sketches showing dowel bars in contraction joint, tie bars in longitudinal joint, expansion joint with filler

Low-Cost Roads:

• Earth Roads: Natural soil, minimal treatment.

• Gravel Roads: Layer of gravel on prepared subgrade.

• Improved Earth: Soil stabilized with lime/cement or surfaced with soil-cement.

• Soil-Cement Roads: Soil + 5-8% cement as base/surface.

Other Definitions:

• Grade Separation: Intersection at different levels (flyover/underpass).

• Types of Horizontal Curves: Simple, Compound, Reverse, Transition.

• Types of Vertical Curves: Summit (convex), Sag (concave).

• Trip Distribution: Allocating trips from origins to destinations in transport planning.

• Seal Coat vs Tack Coat:

  • Tack Coat: Thin bitumen film between layers for bonding.

  • Seal Coat: Thin bituminous layer on top for waterproofing & texture.

• Runway Threshold Lighting: Row of green lights (approach end) & red lights (far end) marking runway beginning/end.

• Wind Rose Diagram: Circular diagram showing wind speed/frequency distribution by direction.

• Rotating Beacon: Airport identification light (white/green for civil, white/yellow for military).

[!TIP] These are very common 2-4 mark questions. Memorize one-line definitions and sketch key diagrams (joints, wind rose, zoning).