JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year TRANSPORTATION ENGINEERING Previous Question Paper (March - 2021 - R18)

Public-Private Partnership (PPP) models in India's highway sector have been instrumental in bridging the funding gap and improving operational efficiency. The National Highways Authority of India (NHAI) primarily utilizes three key frameworks for road development:

1. Build-Operate-Transfer (BOT) Toll: The private partner is responsible for financing, constructing, operating, and maintaining the highway for a specified concession period (typically 20-30 years). The developer recovers the investment through toll collection from road users. This model transfers traffic risk entirely to the private entity.
2. Build-Operate-Transfer (BOT) Annuity: The developer finances and constructs the highway, but the government pays a fixed semi-annual amount (annuity) to the developer over the concession period. Since the government collects the tolls, the developer is shielded from traffic volume risk, making this model more attractive for projects with uncertain traffic projections.
3. Hybrid Annuity Model (HAM): Introduced to revive private investment, this model combines features of both EPC and BOT. The government contributes 40% of the project cost during construction in five equal installments, while the developer arranges the remaining 60%. The government collects the tolls, and the developer receives the remaining 60% as annuity payments, along with interest and O&M costs, during the operational phase.

Additionally, the Engineering, Procurement, and Construction (EPC) model is used where the government funds 100% of the project, and the private sector is hired only for construction. PPP schemes have evolved to mitigate risks, improve project bankability, and ensure timely delivery of national highway infrastructure by leveraging private sector expertise and capital.

The width of the carriage way, also known as the road width or paved width, is determined by the width of the traffic lanes and the number of lanes required to accommodate the design traffic volume. The primary factors governing the width are:

• Width of vehicle: The maximum permissible width of the widest vehicle (usually 2.44 m) dictates the minimum lane width.
• Clearance: Additional lateral clearance is required between vehicles and between the vehicle and the edge of the pavement for safety and maneuvering.
• Design speed: Higher speeds necessitate wider lanes to provide a margin for steering variations and driver comfort.
• Traffic volume and composition: Higher volumes and a higher percentage of heavy commercial vehicles require wider lanes to prevent congestion and side-swiping.
• Horizontal curvature: On sharp curves, extra widening is provided to account for the off-tracking of rear wheels of long wheel-base vehicles.
• Presence of shoulders and curbs: The type of edge treatment influences the effective width required for safe operation.

According to IRC (Indian Roads Congress) specifications, the standard width of a single lane is 3.75 m for a single-lane road and 3.5 m per lane for multi-lane roads. The recommended widths are as follows:

For roads with raised curbs, a minimum utility setback or clearance is often required beyond the carriage way width to ensure safety and drainage efficiency.