Questions
~5 questions
Difficulty
Medium
Importance
High yield for PSU technical papers
Overview
Transportation Engineering in PSU exams focuses on the design, analysis, and safety of road networks. It is a high-scoring module where conceptual clarity on geometric parameters and empirical pavement design formulas leads to quick marks.
Highway Geometric Design
This section covers cross-sectional elements, sight distances, and alignment design. In PSU exams, focus heavily on the relationship between speed, friction, and radius of curvature.
- SSD = vt + v^2/(2g(f ± 0.01n))
- OSD = d1 + d2 + d3
- Super-elevation (e + f = v^2/gR)
- Extra widening = nl^2/2R + v/(9.5 * sqrt(R))
- Transition curve length L = v^3/CR
- Setback distance depends on SSD and horizontal curve radius
Pavement Design
Aspirants must distinguish between flexible pavements (load distribution through grain-to-grain contact) and rigid pavements (slab action). Key emphasis is placed on IRC method design procedures and stress analysis.
- Flexible pavement: CBR method is the standard
- Rigid pavement: Westergaard’s stress analysis
- Radius of relative stiffness l = (Eh^3 / 12k(1-μ^2))^0.25
- Temperature stresses: Warping and frictional stress
- Equivalent Wheel Load Factor (EWLF) for axle load calculation
- Design life for national highways is typically 15-20 years
Traffic Engineering
This subtopic deals with the flow characteristics and safety measures. PSU questions frequently test traffic capacity, volume-density relationships, and intersection signaling.
- Green time calculation: Webster’s method
- Traffic capacity (C = 1000v/s)
- Space Mean Speed vs Time Mean Speed
- Saturation flow rate
- PCU (Passenger Car Unit) values for different vehicles
- Time gap and headways
IRC Codes
Knowledge of standard Indian Roads Congress codes is mandatory for objective questions. Memorizing code numbers for specific design standards is a common hurdle but essential for scoring.
- IRC:37 for Flexible Pavement design
- IRC:58 for Rigid Pavement design
- IRC:67 for Road signs
- IRC:73 for Geometric Design standards
- IRC:35 for Road markings
Formula Sheet
SSD = vt + v^2/(2g(f ± 0.01n))
e + f = v^2/127R
l = (Eh^3 / 12k(1-μ^2))^0.25
C = 1000v/s
Exam Tip
Focus on numerical application of SSD and Super-elevation formulas as they form the bulk of the 5-mark weightage.
Common Mistakes
- Confusing the units in the SSD formula (using kmph instead of m/s)
- Neglecting the effect of centrifugal force on the inner wheel of a curve
- Mixing up warping stress formulas for corner, edge, and interior load positions
More Revision Notes
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