Transportation Engineering- II (CE-502) - Unit 5 Short Notes

UNIT 5: TRANSPORTATION ENGINEERING-II

(Based on RGPV Past Paper Analysis: Jun 2025, May 2024, Nov 2023)

1. HIGHWAY GEOMETRIC DESIGN & ALIGNMENT

Horizontal Curves

Purpose: Provide smooth transition between straight alignments, ensure safety and comfort at direction changes.

Types & Features:

Key Parameters:

• Radius (R): Governs curvature.

• Deflection Angle (Δ): Intersection angle of tangents.

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

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

• Curve Length (L): $$\displaystyle L = \frac{\pi R \Delta}{180} $$

[!TIP] Exam Focus: Derivation of superelevation and OSD calculations are frequently asked.

Superelevation (e)

Definition: Banking of outer edge to counteract centrifugal force.

Derivation (Force Equilibrium):

$$ e + f = \frac{V^2}{gR} $$

Where:

• $e$ = superelevation (m/m)

• $f$ = coefficient of lateral friction (0.15 max, IRC)

• $V$ = design speed (m/s)

• $g$ = acceleration due to gravity (9.81 m/s²)

• $R$ = radius of curve (m)

Design Formula (IRC):

$$ e + f = \frac{V^2}{127R} $$

(V in km/h, R in m)

Maximum Limits (IRC):

• Plain/rolling terrain: $$\displaystyle e_{max} = 7\% $$ (1 in 14.5)

• Hilly terrain: $$\displaystyle e_{max} = 10\% $$

• Superelevation is limited to 4% on urban roads.

[!TIP] Common Pitfall: For mixed traffic, use $$\displaystyle f_{max} = 0.15 $$ only if $e$ is not fully provided.

Overtaking Sight Distance (OSD)

Purpose: Ensure safe overtaking in two-lane roads.

OSD Formula (IRC):

$$ d = d_1 + d_2 + d_3 $$

Where:

• $$\displaystyle d_1 $$ = distance traveled by overtaking vehicle during reaction time (m)

• $$\displaystyle d_2 $$ = distance traveled while overtaking (m)

• $$\displaystyle d_3 $$ = clearance distance (m)

Standard Assumptions:

• Overtaking vehicle speed = $$\displaystyle V_b $$ m/s

• Overtaken vehicle speed = $V$ m/s

• Acceleration = 0.5 m/s²

• Reaction time = 2 sec

• $$\displaystyle d_3 = $$ clearance = 5 m (safe margin)

Numerical Example (Jun 2025):

Given: $$\displaystyle V_b = 70 $$ km/h, $$\displaystyle V = 40 $$ km/h.

Convert to m/s: $$\displaystyle V_b = 19.44 $$ m/s, $$\displaystyle V = 11.11 $$ m/s.

$$ d_1 = V_b \times t = 19.44 \times 2 = 38.88 \text{ m} $$

$$ d_2 = \left[ 2 \times (V_b - V) \times t + \frac{(V_b - V)^2}{a} \right] = \left[ 2 \times 8.33 \times 2 + \frac{(8.33)^2}{0.5} \right] = 33.32 + 138.9 = 172.22 \text{ m} $$

$$ d_3 = 5 \text{ m} $$

$$ \boxed{OSD = 38.88 + 172.22 + 5 = 216.1 \text{ m}} $$

Overtaking Zone Length:

• Minimum length: $$\displaystyle L_{min} = 3 \times OSD $$

• Desirable length: $$\displaystyle L_{des} = 5 \times OSD $$

For OSD = 216.1 m:
$$\displaystyle L_{min} = 648.3 $$ m, $$\displaystyle L_{des} = 1080.5 $$ m.

Signage:

• "NO OVERTAKING" sign at start of zone.

• "OVERTAKING PROHIBITED FOR HEAVY VEHICLES" if applicable.

• Sign placed at least 150 m before overtaking zone.

[!TIP] Sketch Requirement: Show two-lane road with OSD marked, signs at start/end, and vehicle positions during overtaking.

Vertical Curves

Types:

• Summit (Convex): Crest vertical curve.

• Sag (Concave): Valley vertical curve.

Design Considerations:

• Length (L) based on sight distance (SSD/OSD).

• Summit Curve: SSD controls design.

• Sag Curve: SSD + headlight sight distance (night).

Minimum Length Formula (IRC):

For summit: $$\displaystyle L = \frac{A \cdot SSD^2}{(\sqrt{2H_1} + \sqrt{2H_2})^2} $$

Where:

• $$\displaystyle A = |n_2 - n_1| $$ (algebraic difference in grades)

• $$\displaystyle H_1, H_2 $$ = driver’s eye height (1.2 m) & object height (0.15 m)

Off-Tracking

Definition: Rear wheels follow a shorter path than front wheels during turning.

Formula:

$$ \text{Off-tracking (O.T.)} = \frac{L^2}{8R} $$

Where:

• $L$ = wheelbase (m)

• $R$ = radius of path of front outer wheel (m)

Example (Nov 2023):

Given: $$\displaystyle L = 6.5 $$ m, $$\displaystyle R = 32 $$ m.

$$ O.T. = \frac{(6.5)^2}{8 \times 32} = \frac{42.25}{256} = 0.165 \text{ m} $$

[!TIP] Off-tracking is critical for multi-axle vehicles and designing turning radii.

Engineering Surveys for Highway Location

1. Map Study:

   • Topographic maps (1:50,000 to 1:250,000).

   • Identify ridges, valleys, rivers, towns.

   • Preliminary alignment selection.

2. Reconnaissance Survey:

   • Ground inspection of shortlisted alignments.

   • Check terrain, soil, drainage, utilities.

3. Preliminary Survey:

   • Detailed topographic survey (cross-sections, levels).

   • Trial & error method for final alignment.

[!TIP] Map Study Use: Avoids costly field surveys by eliminating impractical routes early.

2. PAVEMENT DESIGN & CONSTRUCTION MATERIALS

Flexible vs Rigid Pavements

[!TIP] Advantage of Rigid: Longer life, less maintenance. Disadvantage: High initial cost, noisy.

A. Flexible Pavements

General Construction Procedure:

1. Sub-grade: Earthwork, compaction to required density.

2. Sub-base/Course: Granular material (GSB), compaction.

3. Base Course: WBM/WMM, compaction.

4. Surface Course: Bituminous layers (BM, BC), rolling.

Design by CBR Method (IRC: 37-2018)

Procedure:

1. Determine CBR value of subgrade soil (soaked, 4-day).

2. Choose design CBR (from traffic, CBR chart).

3. Use IRC:37-2018 charts to get total thickness.

4. Allocate thickness to each layer based on material quality.

Sketch:

[Surface: BC (40-50 mm)]  

[Base: BM (50-100 mm)]  

[Base: WBM/WMM (150-250 mm)]  

[Sub-base: GSB (150-300 mm)]  

[Sub-grade: CBR soil]

Thickness Calculation Example:

If design CBR = 5%, total thickness ≈ 600 mm (from chart).

Bituminous Materials & Constructions

Uses & Limitations of WBM:

• Uses: Economical base course, good for moderate climates.

• Limitations: Poor in heavy rain (stone dust washes out), requires skilled labor, frequent maintenance.

Tack Coat:

• Purpose: Ensure bond between successive bituminous layers.

• Application: Bitumen emulsion (0.2-0.5 kg/m²), sprayed before laying.

Seal Coat:

• Purpose: Seal surface voids, provide skid resistance.

• Application: Single layer of fine aggregate + bitumen (1.2-1.5 kg/m²).

IRC Specifications for Bituminous Concrete (BC)

• Aggregate: Crushed, angular, specific gravity ≥2.6.

• Bitumen: VG-10 or VG-20 (penetration grade).

• Voids: 3-5% in compacted mix.

• Thickness: 40-50 mm (single lift).

• Compaction: ≥95% of Marshall density.

B. Rigid Pavements

General Construction Procedure:

1. Sub-grade: Compact to ≥95% Proctor density.

2. Sub-base: Granular (150 mm min), if required.

3. Concrete Placement:

   • Mix design (M30 to M40).

   • Slip-form or fixed-form paving.

4. Curing: 14 days minimum (wet burlap, curing compound).

5. Jointing: Saw-cut within 6-24 hours.

6. Sealing: Joints with pre-moulded filler + sealant.

IRC 58-2002 Design Method

Steps:

1. Determine design traffic (ESA - Equivalent Single Axle Loads).

2. Select modulus of elasticity of concrete ($$\displaystyle E_c $$).

3. Modulus of subgrade reaction ($k$) from plate bearing test.

4. Stress analysis:

   • Load stress (Westergaard’s equations).

   • Temperature stress (warping, frictional).

5. Thickness calculation:

$$ h = \sqrt[3]{\frac{3P}{2E_c \Delta} \left( \frac{k}{E_c} \right)^{1/3} \cdot a^2 } $$

(Corner stress model)

6. Check for edge and corner stresses.

Sketch:

[Concrete slab (h mm)]  

[Sub-base (100-150 mm)]  

[Sub-grade]

Joints in Rigid Pavement

Dowel Bars:

• Material: Mild steel, smooth round.

• Function: Transfer load across expansion joints, allow horizontal movement.

• Placement: Mid-depth, parallel to surface.

Tie Bars:

• Material: Deformed steel.

• Function: Hold adjacent slabs together, prevent separation.

• Placement: Across longitudinal/contraction joints.

IRC Specifications for Cement Concrete Pavement

• Concrete grade: M30 to M40.

• Slab thickness: 150-400 mm (based on traffic).

• Joint spacing: Expansion joints 50-90 m; contraction joints 3-5 m.

• Curing: 14 days minimum.

• Joint sealant: Hot-poured bitumen or silicone.

C. Soil Stabilization

Scope & Importance:

• Improve subgrade strength (CBR, UCS).

• Reduce swelling/shrinkage (clays).

• Economical alternative to soil replacement.

Mechanical Stabilization:

• Methods:

  1. Soil grading: Blend coarse/fine fractions to get well-graded mix.

  2. Compaction: Increase density, reduce voids.

• Procedure:

  • Determine optimum moisture content (OMC) & max dry density (MDD) from Proctor test.

  • Mix soils if necessary, compact in layers.

• Applications:

  • Sub-base in low-traffic roads.

  • Embankments in poor soils.

[!TIP] Chemical Stabilization (lime, cement) is for high-strength requirements; mechanical is for granular improvement.

D. Low-Cost Roads

Definition: Roads constructed with locally available materials at minimal cost, suitable for low traffic (rural/agricultural).

Types:

1. Earth Roads:

   • Material: Natural soil.

   • Construction: Compaction, drainage provisions.

   • Limitation: Poor in rain, dust in summer.

2. Gravel Roads:

   • Material: Gravel or crushed stone.

   • Construction: Layer thickness 150-250 mm, crowned, side drains.

   • Maintenance: Periodic regrading, gravel replenishment.

3. Water Bound Macadam (WBM):

   • Material: Stone aggregate + stone dust + water.

   • Use: Intermediate cost, base course.

3. TRAFFIC ENGINEERING & STUDIES

A. Traffic Studies

Speed Studies

Methods:

• Enoscope: For spot speed (visual).

• Radar Gun: Instantaneous speed.

• Photographic: High accuracy.

Origin-Destination (O-D) Studies

Purpose:

• Trip generation & distribution.

• Planning new roads, public transport.

• Traffic assignment.

Data Collection Methods:

1. Home Interview: Detailed, expensive.

2. Roadside Interview: At cordon lines.

3. Postal Survey: Questionnaires.

4. Tagging: Number plates recorded.

Trip Distribution Models:

• Gravity Model: $$\displaystyle T_{ij} = k \frac{P_i^\alpha \cdot Q_j^\beta}{C_{ij}^\gamma} $$

  Where $$\displaystyle T_{ij} $$ = trips from i to j, $$\displaystyle P_i, Q_j $$ = trip productions/attractions, $$\displaystyle C_{ij} $$ = travel cost.

• Growth Factor Method: Simple multiplication.

Parking Studies

Purposes:

• Determine parking demand.

• Design parking facilities.

• Evaluate parking turnover.

On-Street Parking Methods:

• Parallel: 2.5-3.5 m width, least space, causes obstruction.

• Angle (30°-60°): More capacity, easier parking.

• Perpendicular (90°): Max capacity, needs more width.

B. Traffic Control Devices

Road Markings

Road Lighting

Design Factors (CIE):

1. Luminance: ≥ 2 cd/m² (main roads).

2. Uniformity Ratio: Min/Max luminance ≥ 0.4.

3. Glare Control: Luminaire design.

4. Mounting Height: 8-12 m (high mast for intersections).

5. Spacing: Based on luminaire output, 3-5 times mounting height.

C. Intersection Design

Grade Separated Intersections

Types:

• Flyover (Overpass): One road elevated.

• Underpass: One road depressed.

• Rotary: Central island, continuous flow.

Advantages:

• No crossing conflicts.

• High capacity, speed.

Limitations:

• Very high cost.

• Land requirement.

• Not suitable for low traffic.

4. AIRPORT PLANNING & DESIGN

A. Fundamentals

Airport Classification (ICAO)

Based on runway length & aircraft wingspan:

Site Selection Factors

1. Topography: Flat terrain, minimal earthwork.

2. Wind Direction: Wind Rose Diagram shows predominant wind direction (runway aligned with wind).

3. Obstructions: Clear approach cones (no buildings, hills).

4. Approach Areas: Unobstructed funnel-shaped zones.

5. Soil: Good bearing capacity.

6. Future Expansion: Available land.

Wind Rose Diagram:

• Types:

  • Directional: Shows wind speed by direction.

  • Speed-frequency: % time wind blows at certain speed.

• Application: Determine runway orientation (max wind coverage ≥ 95%).

Aircraft Characteristics

Sketches Required:

• Aircraft plan/side view with dimensions marked.

• Runway/taxiway layout showing separation.

B. Runway Design

Geometric Elements:

• Length: Based on aircraft performance.

• Width: 45-60 m (ICAO).

• Orientation: Wind-rose aligned.

• Gradient: Max 1.5% (2% for code 4).

• Safety Areas: 150 m (ends), 75 m (sides).

Runway Length Correction

Standard Conditions:

• Sea level, 15°C, zero gradient, no wind, standard aircraft weight.

Corrections:

1. Elevation Correction:

$$ \Delta L_1 = \frac{L \times e}{600} $$

(e = elevation in 100 m units)

2. Temperature Correction:

$$ \Delta L_2 = L \times \frac{1}{600} \times (T_m - 15) $$

Where $$\displaystyle T_m $$ = mean monthly max temp (°C).

3. Gradient Correction:

$$ \Delta L_3 = L \times \frac{\text{gradient (\%)}}{100} $$

Corrected Length:

$$ L_{corrected} = L_{standard} + \Delta L_1 + \Delta L_2 + \Delta L_3 $$

Example (Jun 2025):
$$\displaystyle L_{std} = 2050 $$ m, $$\displaystyle e = 420 $$ m, $$\displaystyle T_m = 35°C $$, gradient = 0.3%.

$$ \Delta L_1 = \frac{2050 \times (420/100)}{600} = \frac{2050 \times 4.2}{600} = 14.35 \text{ m} $$

$$ \Delta L_2 = 2050 \times \frac{1}{600} \times (35-15) = 2050 \times \frac{20}{600} = 68.33 \text{ m} $$

$$ \Delta L_3 = 2050 \times \frac{0.3}{100} = 6.15 \text{ m} $$

$$ \boxed{L_{corr} = 2050 + 14.35 + 68.33 + 6.15 = 2138.83 \text{ m}} $$

Runway Lighting

Threshold Lighting:

• Configuration: Row of lights across runway threshold.

• Components:

  • End lights: Red (far end), green (approach end).

  • Wing bars: Extend outward.

  • Centerline lights: White (first 900 m), alternating red/white, red (last 300 m).

Other Systems:

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

• Centerline: White (high intensity).

• Touchdown Zone: White (first 900 m).

C. Airport Capacity & Zoning

Airport Capacity

• Hourly Capacity: Max aircraft movements/hour (arrivals+departures).

• Annual Service Volume (ASV): Design capacity/year (considering peak hour).

Factors Affecting Capacity:

1. Runway Configuration: Single/parallel/intersecting.

2. Aircraft Mix: Heavy vs light aircraft separation.

3. ATC Efficiency: Radar, separation minima.

4. Weather: Visibility, wind.

5. Taxiway Layout: Congestion points.

Zoning Regulations (ICAO)

Purpose: Obstacle clearance for approach.

Figures:

• Approach Surface: 1500 m wide at threshold, expands outward.

• Conical Surface: 3000 m radius.

• Horizontal Surface: 10000 m radius.

D. Navigational Aids

Instrument Landing System (ILS)

Components:

1. Localizer: Lateral guidance (110-112 MHz).

2. Glide Slope: Vertical guidance (329-335 MHz).

3. Marker Beacons: Distance indication (75 MHz):

   • Outer Marker (OM): 7-10 km from threshold.

   • Middle Marker (MM): 1000 m from threshold.

   • Inner Marker (IM): 100 m from threshold (CAT II/III).

Categories:

• CAT I: DH 60 m, RVR 550 m.

• CAT II: DH 30 m, RVR 300 m.

• CAT IIIa: DH < 15 m, RVR 200 m.

• CAT IIIb: DH < 15 m, RVR 50 m.

• CAT IIIc: No DH/RVR limits (rare).

Precision Approach Radar (PAR)

• Purpose: Provide precise approach guidance in poor weather.

• Operation: Ground-based radar tracks aircraft position, gives azimuth/elevation corrections to pilot.

• Used where ILS not available or as backup.

E. Other Airport Facilities

Taxiway Design

• Design Speed: 30-50 km/h (lower than runway).

• Width: 15-23 m (based on code).

• Separation from Runway: Min 150 m (parallel), 90 m (crossing).

Rotating Beacon

• Purpose: Night identification of airport location.

• Color: Green/white (civil), white/white (military).

• Location: Elevated, near control tower.

5. INSTITUTIONAL & MISCELLANEOUS

Road Classification (IRC)

Research & Funding Organizations

[!TIP] Short Notes Focus: Define each org + one key function.

END OF UNIT 5
Prepared for RGPV CE-502 - Transportation Engineering-II (Past Paper Aligned)