UNIT 3: TRANSPORTATION ENGINEERING-II (CE-502) - SHORT NOTES

Based on rigorous analysis of RGPV past papers (Jun 2025, May 2024, Nov 2023).

1.0 GEOMETRIC DESIGN OF HIGHWAYS

1.1 Horizontal Alignment

Purpose: To provide a smooth and safe transition in direction between two straight sections (tangents) of a road, ensuring driver comfort, vehicle stability, and adequate sight distance.

Types of Horizontal Curves:

Key Elements of a Simple Circular Curve:

• Radius (R): Constant radius of the curve.

• Deflection Angle (Δ): Angle between the two tangents (in degrees).

• Tangent Length (T): Distance from PI (Point of Intersection) to BC (Beginning of Curve) or EC (End of Curve). $$\displaystyle T = R \tan(\Delta/2) $$

• Length of Curve (L): $$\displaystyle L = \frac{\pi R \Delta}{180} $$ (in meters, Δ in degrees).

• Chainage: Sequential distance along the alignment from a fixed starting point. BC Chainage = PI Chainage - T.

Design of Superelevation (e):

• Purpose: To counteract the effect of centrifugal force on a vehicle negotiating a curve, improving safety and comfort.

• Derivation: For equilibrium, the component of centrifugal force along the superelevated surface is balanced by the component of vehicle weight.

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

Where:

*   $e$ = rate of superelevation (max 7% per IRC for plain/rolling terrain)

*   $f$ = coefficient of lateral friction (max 0.15 per IRC)

*   $V$ = design speed (m/s)

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

*   $R$ = radius of curve (m)

• IRC Formula (for mixed traffic):

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

(Where $V$ is in km/h, $R$ in m).

• Design Steps:

  1. Calculate $e + f$ for given $V$ and $R$.

  2. Provide maximum $$\displaystyle f = 0.15 $$ (IRC). Calculate required $e$.

  3. If $$\displaystyle e_{calc} > 0.07 $$ (max limit), design for $$\displaystyle e = 0.07 $$ and find minimum radius ($$\displaystyle R_{min} $$) for that $V$.

  4. Determine length of superelevation runoff based on gradient (IRC: 1 in 150 to 1 in 60).

[!TIP] Exam Focus: You will be asked to derive the expression and/or calculate 'e' for given $V$ and $R$. Always check if $e$ exceeds 7% and adjust radius accordingly.

Off-Tracking & Turning Paths:

• Off-Tracking (Swept Path): The difference between the paths of the front and rear wheels of a long vehicle (like a truck) while turning. The rear wheels follow a path of smaller radius than the front wheels.

• Calculation (for a simple circular curve):

$$Off\text{-}tracking (OT) = L - \sqrt{L^2 - (R - OT)^2} \approx \frac{L^2}{2R}$$

Where:

*   $L$ = wheelbase of the vehicle (m)

*   $R$ = radius of the path of the **front outer wheel** (m).

*   $OT$ = off-tracking (m).

*   **Simplified Formula:** $$\displaystyle OT \approx \frac{L^2}{2R} $$ (for small angles).

[!TIP] Common Pitfall: Ensure you use the correct radius (usually the radius of the front outer wheel path or the mean radius of the curve as specified in the problem).

1.2 Sight Distance

Stopping Sight Distance (SSD): Minimum distance required for a driver to see an object and stop the vehicle safely.

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

Where:

• $V$ = design speed (km/h)

• $t$ = brake reaction time (2.5 sec, per IRC)

• $f$ = coefficient of longitudinal friction (0.35 to 0.4)

• $G$ = gradient (+ for ascending, - for descending) in %

Overtaking Sight Distance (OSD): Minimum distance required for a driver to overtake a slower vehicle safely in the face of oncoming traffic. For Two-Way Traffic on Single-Lane Road (IRC method):

$$OSD = d_1 + d_2 + d_3$$

Where:

1. $$\displaystyle d_1 $$ = Distance travelled by overtaking vehicle during perception/reaction and initial acceleration to occupy the overtaking lane.

   $$\displaystyle d_1 = 0.278V_b t_1 + \frac{(V_b - V_f)^2}{2a} $$ (simplified: $$\displaystyle d_1 \approx 0.278V_b t_1 $$ if $$\displaystyle V_b \approx V_f $$ initially)

2. $$\displaystyle d_2 $$ = Distance covered by overtaking vehicle while occupying the opposing lane.

   $$\displaystyle d_2 = 0.278[sV_b + 2V_b + V_a]T $$ (Simplified IRC formula: $$\displaystyle d_2 = 0.278V_b T $$)

   • $s$ = spacing between vehicles (often taken as 1.5 to 2 sec headway)

   • $T$ = overtaking time (given or calculated)

3. $$\displaystyle d_3 $$ = Distance travelled by opposite direction vehicle during the overtaking maneuver.

   $$\displaystyle d_3 = 0.278V_a T $$

[!TIP] Numerical Strategy: If $$\displaystyle V_a $$ (opposite vehicle speed) is not given, assume it equals the design speed $V$. Use the simplified OSD formula from IRC if provided in textbooks: $$\displaystyle OSD = 0.278V \left[ t_1 + T + \frac{d_2}{V} \right] + \frac{d_3}{V} $$.

Overtaking Zone:

• Minimum Length: Should accommodate at least one complete overtaking maneuver for a slow-moving vehicle. Approximately equal to OSD.

• Desirable Length: Should allow two or more overtaking maneuvers. Typically 3 to 4 times OSD.

• Location of Signposts: "Overtaking Zone Ahead" sign placed at a distance equal to OSD before the start of the overtaking zone. "End of Overtaking Zone" sign at the end.

1.3 Vertical Alignment

Types of Vertical Curves:

• Summit Curve (Convex): Formed when two gradients meet at a peak. Critical for SSD (headlight sight distance at night).

• Sag Curve (Concave): Formed when two gradients meet at a valley. Critical for SSD (headlight sight distance at night) and drainage.

Design Considerations:

1. Sight Distance: Primary criterion for length of curve ($L$). For SSD on summit curve:

$$L = \frac{NS^2}{(\sqrt{h_1} + \sqrt{h_2})^2}$$

Where $N$ = deviation angle, $$\displaystyle h_1, h_2 $$ = driver's eye and object heights (1.2m, 0.15m), $S$ = SSD.

2. Comfort: Avoid abrupt changes in gradient to prevent discomfort. Use parabolic curves (most common).

3. Drainage: On sag curves, ensure adequate length and gradient for surface runoff; may require inlets.

Grade (Gradient): The rate of rise or fall of the road surface expressed as a percentage ($$\displaystyle \frac{rise}{run} \times 100 $$). Steeper gradients reduce vehicle speed, increase fuel consumption, and affect design speed and capacity.

2.0 PAVEMENT DESIGN & MATERIALS

2.1 Flexible Pavements

Component Layers (Top to Bottom):

1. Surface Course (Wearing Course): BC/Dense Bituminous Macadam. Provides smooth, durable, skid-resistant surface.

2. Binder Course: Bituminous Macadam/Concrete. Distributes loads.

3. Base Course: WMM/WBM. Major load distribution layer.

4. Sub-base Course: (Optional) Lower quality material, provides separation/filtration.

5. Sub-grade: Compacted natural soil. Foundation.

Design by CBR Method (IRC:37-1970):

• CBR (California Bearing Ratio): A measure of sub-grade strength. Ratio (%) of load required to penetrate a soil sample to load required for standard crushed stone.

$$CBR = \frac{Load at penetration for soil}{Load at penetration for standard material} \times 100\%$$

• Procedure:

  1. Determine design CBR value of sub-grade (from lab/field tests, usually at 95% Proctor density, soaked condition for worst-case).

  2. Use IRC design charts (Fig. 2, IRC:37-1970) relating:

     • X-axis: CBR (%)

     • Y-axis: Total pavement thickness (cm) for a given design wheel load (usually 4080 kg for single axle) and number of standard axles (e.g., 10^6, 10^7).

  3. Read total thickness ($T$) for given CBR and traffic.

  4. Distribute thickness among layers based on material quality and IRC guidelines (e.g., top 2-3 layers bituminous, bottom layers granular).

• Sketch: Show multi-layer system with thicknesses $$\displaystyle T_1, T_2, ... $$ summing to $T$.

[!TIP] Exam Problem: Given CBR value, traffic (in msa), find total pavement thickness. Then allocate to layers (e.g., BC 5cm, BM 7cm, WMM 22cm, GSB 20cm).

Construction: Water Bound Macadam (WBM)

• Materials:

  • Aggregates: Crushed, hard, durable stone. Grading as per Table 400.1 (IRC:19).

  • Binding Material: screenings (fine aggregate) to fill voids.

  • Water: For compaction and grouting.

• Procedure:

  1. Preparation: Sub-base compacted and trimmed.

  2. Laying: Coarse aggregates spread in layers (6-8 cm loose), rolled with 8-10 ton roller.

  3. Application of Screenings: Fine aggregate spread and rolled to fill interstices.

  4. Grouting: Wet slurry of fine aggregate and water applied to fill voids completely.

  5. Setting & Curing: After final rolling, allowed to set. Curing not typically required, but keep moist for 24 hrs.

• Uses: Base course for flexible pavements, shoulders.

• Limitations: Dusty, not waterproof, requires regular maintenance, poor riding quality.

Bituminous Macadam (BM) / Wet Mix Macadam (WMM):

• BM: Aggregates + hot bitumen. Laid hot and rolled.

• WMM: Aggregates + water (no bitumen). Used as sub-base or base (better than WBM). More stable, less dust.

Bituminous Concrete (BC):

• IRC Specifications (IRC:58-1992):

  • Materials: Crushed aggregates, filler (stone dust/lime), bitumen (VG-10/VG-20).

  • Grading: Dense, gap-graded (Table 500.16).

  • Construction: Hot mix plant, laid at 120-150°C, compacted with 8-10 ton roller then pneumatic tyred roller.

  • Thickness: 40-50 mm for wearing course.

  • Maintenance: Patching with premix material; surface renewal by scarifying and overlaying.

Tack Coat & Seal Coat:

• Tack Coat: Thin application of emulsified bitumen (RS-1, SS-1) on existing surface before laying new layer. Purpose: Ensure bond between layers.

• Seal Coat: Thin layer of open-graded premix (1-2 cm) over existing pavement. Purpose: Seal surface cracks, provide skid resistance, prevent water ingress.

2.2 Rigid Pavements (Cement Concrete)

Advantages:

• Long life (20-40 yrs), high load-spreading capacity, less maintenance, fuel-efficient riding surface, usable in all weather. Disadvantages:

• High initial cost, noisy, requires high-quality materials & skilled labor, difficult to repair, long curing time.

Design by IRC Method (IRC:58-2002 - Brief Outline):

1. Considerations: Design wheel load (4080 kg), material properties (modulus of elasticity $$\displaystyle E_c $$, Poisson's ratio $\mu$), temperature/drying stresses.

2. Stresses: Compute critical flexural stress at bottom of slab under wheel load and temperature stress (edge or corner).

3. Thickness (h): Determined by equating bending stress to allowable flexural strength of concrete (typically 4-5 MPa). Uses Westergaard's theory.

$$\sigma_{max} = \frac{P}{h^2} \times f \text{ (where f is a function of } L, \Delta, \text{ and slab geometry)}$$

Solve for $h$.

4. Reinforcement: For contraction joints (to hold slabs together) and continuous slabs (to control cracking). Uses steel bars (dowel/tie bars).

Joints in Rigid Pavements:

• Dowel Bars: Smooth, round, placed across transverse joints. Function: Transfer load across joint while allowing horizontal movement (expansion/contraction).

• Tie Bars: Deformed, placed along longitudinal/contraction joints. Function: Hold adjacent slabs together, prevent separation.

2.3 Soil Stabilization

Need: Improve sub-grade strength (CBR), reduce swelling/shrinkage, increase durability, reduce construction cost on weak soils.

Methods:

1. Mechanical Stabilization: Mixing inferior soil with granular material (sand, gravel) and compacting. Increases density, reduces plasticity.

2. Chemical Stabilization:

   • Lime Stabilization: For clayey soils. Reduces plasticity, increases strength via pozzolanic reactions.

   • Cement Stabilization: For sandy/silty soils. Acts as a binder.

   • Bitumen Stabilization: For granular soils. Waterproofs and binds.

3. Other: Geo-synthetics (geogrids, geotextiles) for reinforcement/separation.

2.4 Low-Cost Roads

• Definition: Roads constructed with locally available materials and low-cost technology, providing basic all-weather connectivity at minimal cost.

• Types:

  1. Earth Roads: Compacted natural soil. Construction: Clearing, shaping, compacting in layers. Maintenance: Frequent grading, drainage maintenance.

  2. Gravel Roads: Layer of gravel on prepared sub-grade. Construction: Spread and compact gravel. Maintenance: Reshaping, adding gravel, dust control.

  3. Improved Unpaved Roads: Use of stabilized soil (lime/cement) or surface dressing (thin bituminous layer) on gravel/earth base.

3.0 TRAFFIC ENGINEERING & SAFETY

3.1 Traffic Studies & Analysis

Speed Studies:

• Spot Speed: Speed at a specific point (measured by radar/enforcement).

• Running Speed: Average speed while moving, excluding stops.

• Time-Mean Speed ($$\displaystyle V_t $$): Arithmetic mean of speeds of vehicles at a point over time. $$\displaystyle V_t = \frac{\sum v_i}{n} $$

• Space-Mean Speed ($$\displaystyle V_s $$): Harmonic mean of speeds of vehicles occupying a section at a given instant. $$\displaystyle V_s = \frac{n}{\sum (1/v_i)} $$

• Average Speed: Often used interchangeably; context matters.

• Method: Radar gun, pneumatic road tubes (for $$\displaystyle V_s $$), moving car observer method.

Origin-Destination (O-D) Studies:

• Purpose: Determine trip origins, destinations, purposes, modes, and routes. Used for:

  • Traffic forecasting, trip assignment, planning new facilities, evaluating existing systems.

• Methods:

  1. Home Interview Survey: Most accurate, detailed but costly.

  2. Roadside Interview Survey: At cordon lines/intersections. Faster, less detailed.

  3. Postal/Telephone Survey.

  4. Tagging Methods: (Number plate matching, automatic vehicle identification).

Trip Distribution: The process of distributing trips from origins to destinations based on socio-economic factors and attraction/ production of zones. Uses models like Gravity Model: $$\displaystyle T_{ij} = k \frac{P_i^\alpha A_j^\beta}{C_{ij}^\gamma} $$

Where $$\displaystyle T_{ij} $$ = trips from zone $i$ to $j$, $$\displaystyle P_i $$ = production, $$\displaystyle A_j $$ = attraction, $$\displaystyle C_{ij} $$ = travel cost/time, $k,\alpha,\beta,\gamma$ = parameters.

Parking Studies:

• Purposes: Determine parking demand, design facilities, set pricing, enforce regulations.

• Methods of On-Street Parking:

  • Parallel: Vehicles parallel to curb. Most space-efficient, least disruptive to traffic.

  • Angle (30°, 45°, 60°, 90°): Vehicles at angle to curb. Higher turnover, more space required, more disruptive.

3.2 Road Markings & Signage

Traffic Markings (IRC:67):

Road Sign Categories (IRC:67):

1. Regulatory (Mandatory): Red circle/blue rectangle. Tell what MUST be done (Speed limit, No entry, One way).

2. Warning (Cautionary): Red triangle. Warn of hazards ahead (Curve, Pedestrian, School).

3. Informatory (Guide): Blue/Green rectangle. Provide information (Place names, Directions, Facilities).

3.3 Road Lighting & Intersections

Design Factors for Road Lighting:

1. Luminance (cd/m²): Brightness of road surface as seen by driver. Primary design criterion.

2. Uniformity Ratio: Min luminance / Average luminance. Should be >0.3.

3. Glare: Disability/Discomfort glare from luminaires. Controlled by mounting height, shielding.

4. Lighting Level: Varies with road class (expressway > major arterial > residential).

5. Colour Rendering: Good colour rendering for object recognition.

Grade Separated Intersections:

• Types: Flyovers (overpass), Underpasses, Interchanges (system of connecting roads at different levels).

• Advantages: Eliminate conflict points, increase capacity, reduce delays, improve safety.

• Limitations: Very high cost, require large land, long weaving lengths, not suitable for all locations.

4.0 AIRPORT PLANNING & DESIGN

4.1 Airport Planning & Site Selection

Objectives: Provide safe, efficient, economical air transportation; accommodate future growth; minimize environmental impact.

Factors for Site Selection:

1. Topography: Relatively flat, adequate area for runways/taxiways/aprons. Avoid steep slopes.

2. Wind: Prevailing wind direction should align with runway orientation (to minimize crosswinds). Analyze Wind Rose Diagram.

3. Obstructions: Clear approach areas (no tall buildings/trees/hills). Enforce zoning regulations.

4. Accessibility: Good ground connectivity (road/rail).

5. Soil Conditions: Good bearing capacity for pavements.

6. Environmental & Social: Noise impact, land acquisition, ecological sensitivity.

7. Future Expansion: Availability of land for growth.

Zoning Regulations (ICAO Annex 14):

1. Approach Surface: Frustum of a pyramid/cone at runway end. Slope 1:50 to 1:75. Most critical for obstructions.

2. Transitional Surface: Sloping outward from approach/runway surfaces. Slope 1:2.

3. Horizontal Surface: Horizontal plane at 45m above aerodrome elevation (for smaller airports) or 150m (for larger).

4. Conical Surface: Sloping surface connecting horizontal surface to outer horizontal surface.

[!TIP] Sketch Required: Draw a 3D perspective showing these surfaces around a runway.

4.2 Aircraft Characteristics

Physical Characteristics (affecting design):

• Wingspan (W): Determines taxiway width, ** apron parking spacing**, gate size.

• Length (L): Affects apron layout, taxiway length, gate position.

• Tail Height (H): Determines clearance under bridges/overpasses.

• Wheelbase (A) & Main Gear Width (M): Determine taxiway turning radius, runway/taxiway width.

• Cockpit Eye Height: For visual aids design.

Performance Characteristics:

• Take-off/Landing Distance: Determines minimum runway length.

• Take-off/Landing Speed: Affects runway length, separation minima.

• Climb Gradient: Affects approach slope, obstacle clearance.

Effect on Design (with Sketches):

• Runway Alignment: Should match prevailing wind direction (within 15° for Category II/III).

• Taxiway Design: Width based on main gear width + clearance. Turning radius based on wheelbase.

• Apron Layout: Gate positions based on aircraft length/wingspan. Parking stands designed for specific aircraft groups (ICAO Aerodrome Reference Code: 1-4 based on wingspan, tail height).

4.3 Runway Design

Geometrical Elements:

• Length: Primary factor.

• Width: Based on Aerodrome Reference Code (e.g., 45m for Code 4C).

• Shoulders: Graded shoulders on each side (typically 2.5-5m).

• Blast Pads: Displaced threshold area to protect runway from jet blast erosion.

• Runway End Safety Areas (RESA): Graded area beyond runway end for safety.

Runway Length Correction: Standard Conditions (ISA, Sea Level, 0% Gradient): $$\displaystyle L_{std} $$ given. Corrections (ICAO Annex 14):

1. Elevation Correction: $$\displaystyle L_{ elev } = L_{std} \times \frac{(1 - 0.0065 \times Elev/288.15)}{(1 - 0.0065 \times 0/288.15)} $$ (Simplified: $$\displaystyle L_{ elev } = L_{std} \times (1 + 0.0001 \times Elev) $$ approx.)

2. Temperature Correction: First find Reference Temperature ($$\displaystyle T_{ref} $$) = Mean daily max temp of hottest month + (0.5 × daily range). Then:

$$L_{temp} = L_{elev} \times \left[ \frac{T_{ref} + 273.15}{288.15} \right]^{0.5} \text{ (or use simplified factor)}$$

3. Effective Gradient Correction: If runway gradient $G$ (%) > 0.2% (upward), increase length.

$$L_{corrected} = L_{temp} \times \left(1 + \frac{G}{100}\right)$$

[!TIP] Numerical Problem: Given $$\displaystyle L_{std} $$, Elevation, $$\displaystyle T_{ref} $$, Gradient $G$. Apply corrections sequentially: $$\displaystyle L_{elev} \rightarrow L_{temp} \rightarrow L_{corrected} $$. Final answer must be rounded up to next 50m or 150ft as per ICAO.

Runway Capacity: Maximum number of movements (arrivals+departures) that can be handled per unit time. Affected by:

• Number & configuration of runways.

• Separation minima (between aircraft).

• ATC efficiency.

• Mix of aircraft (heavy vs. light).

• Weather (visibility, wind).

4.4 Airport Lighting & Visual Aids

Runway Lighting System:

• Threshold Lights: Green (approach end), Red (displaced threshold/stopway end).

• Edge Lights: White (runway center 3/4), Yellow (last 2000ft/600m or 1/4 from each end).

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

• Touchdown Zone Lights (TDZL): Row of white lights in two rows, 30m long, 450m from threshold.

Taxiway Lighting: Blue edge lights, green centerline lights.

Approach Lighting System (ALS): Array of lights extending from runway threshold into approach area. Provides visual reference for alignment and descent. Types: ALS (Simple), ALSF-1, ALSF-2 (with sequence flashing lights).

Rotating Beacon: White-green light. Purpose: Locate airport at night. Location: Usually on or near control tower.

Instrument Landing System (ILS): Provides lateral (localizer) and vertical (glideslope) guidance to aircraft on final approach.

• Components: Localizer antenna (runway end), Glideslope antenna (beside runway), Marker beacons (Outer, Middle, Inner), DME (optional).

• Function: Aircraft receiver interprets signals to stay on correct path.

Precision Approach Radar (PAR): Ground-based radar providing precision approach guidance (both lateral and vertical) to controllers, who then give voice guidance to pilot. Used where ILS not available or as backup.

4.5 Airport Classification & Other Facilities

Airport Classification (ICAO/FAA):

• Based on Aerodrome Reference Code: 1-4 (size) and A-F (aircraft type). E.g., Code 4E (large jets like B747).

• Based on Function: International, Domestic, Regional, General Aviation, Military.

• Based on Traffic: Primary ( > 10,000 pax/yr), Non-primary.

Taxiway: Paved area connecting runways, aprons, terminals. Purpose: Allow aircraft movement without using runway. Design Speed: 30-50 km/h.

Wind Rose Diagram:

• Types:

  1. Directional Wind Rose: Shows % frequency of wind from each direction.

  2. Speed Wind Rose: Shows % frequency of wind speed ranges from each direction.

  3. Resultant Wind Rose: Vector sum of wind speed/direction over period.

• Application in Airport Planning: Determines optimal runway orientation (align with prevailing wind direction to minimize crosswind component). Aim for crosswind component < 15-20 km/h (ICAO).

5.0 INSTITUTIONAL & MISCELLANEOUS TOPICS

5.1 Indian Road Congress (IRC) & Related Bodies

• Indian Road Congress (IRC): Apex body for road development in India.

  • Functions: Formulate standards (codes like IRC:58, IRC:37), recommend policies, promote research, organize seminars.

• Central Road Research Institute (CRRI): Premier R&D institute under Ministry of Road Transport. Conducts research on materials, design, construction, maintenance.

• Central Road Fund (CRF): Funding mechanism (levy on petrol/diesel) for development & maintenance of National/State roads.

• Highway Research Board (HRB): Under National Academy of Sciences. Coordinates research, publishes Indian Highways journal.

5.2 Engineering Surveys for Highway Location

1. Map Study: Topographic maps (Survey of India) to identify possible corridors, major features (rivers, towns), constraints.

2. Reconnaissance Survey: Initial ground visit to verify map info, assess general terrain, soil, drainage, identify preliminary alignments.

3. Preliminary Survey: Detailed topographic survey (cross-sections, levels) for 2-3 alternative alignments. Traffic surveys, soil exploration.

4. Detailed Survey: Final alignment fixed. Detailed geometric design, final cross-sections, property boundaries, structure locations. Final location survey.

5.3 Traffic Control Devices (Recap)

• Road Markings: As in 3.2 (Longitudinal, Transverse, Object).

• Road Signs: As in 3.2 (Regulatory, Warning, Informatory). Must conform to IRC:67.

END OF UNIT 3 NOTES