Public Infrastructure, Transportation, and Water Systems
This domain covers roads, railways, bridges, and water infrastructure. For transportation, understand road classification, geometric design (horizontal and vertical alignment, sight distance, superelevation), pavement structure, and drainage. Traffic questions test capacity, level of service, and intersection design. Bridge questions test load models, bearings, and expansion joints.
Water systems include supply, distribution, sewerage, and treatment. Know the components of a water supply network, pressure requirements, and the principles of wastewater collection (gravity sewers, gradients, manholes) and treatment stages. Stormwater management requires understanding runoff, infiltration, and sustainable drainage. Public infrastructure planning involves demand forecasting, phasing, and asset management.
Traps
A common trap is confusing stopping sight distance with passing sight distance, or forgetting that superelevation and friction jointly resist lateral force. In water systems, questions often test whether you recognize that sewers rely on gravity and self-cleansing velocity, while water mains rely on pressure. Another trap is treating a treatment plant's stages as interchangeable; primary, secondary, and tertiary stages serve different purposes.
Rule of thumb
For sewer design, ensure a self-cleansing velocity (commonly around 0.6–0.75 m/s at design flow) and adequate gradient; for water mains, maintain minimum residual pressure at the farthest point. Always check both capacity and serviceability criteria.