--- title: "Cross-sectional elements of a highway" subject: "Transportation Engineering I" chapter: 3 key: "semester_6/transportation_engineering_i:cross-section-elements" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/cross-section-elements site: BCT Engineering --- # Cross-sectional elements of a highway Transportation Engineering I · Chapter 3: Geometric Design of Highway - Asked in: 2080 Chaitra, 8 marks; 2076 Bhadra (asked 2 times) - Video: [highway cross section elements](https://www.youtube.com/watch?v=IqfsXPoPSd8) — Harshada Nilesh Wagh - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/cross-section-elements - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-3 ## Question Explain the cross-sectional elements of a typical highway section with a neat sketch. ## Short answer A highway cross-section includes carriageway (lanes 3.0-3.75 m), shoulders, camber (2-3%), kerbs, median, side drains, side slopes, formation width (carriageway plus shoulders), and right of way (total land). Urban roads add footpaths, cycle tracks, and service roads. ## Answer The cross-section of a highway shows its elements in a section cut at right angles to the centre line. The main elements are: ```text |<-------------- Right of way ------------------>| |<--------- Formation width -------->| _ shoulder carriageway shoulder _ \ ____________ ___/^\___ ____________ / \/ kerb/edge camber crown \/ drain =========================== drain ``` 1. **Carriageway (pavement):** the portion of the road meant for vehicles; it consists of lanes. Lane width is 3.0-3.75 m (3.5 m typical for NH), depending on class, speed and terrain (NRS 2070/IRC). 2. **Shoulders:** strips on both sides of the carriageway (1.5-2.5 m); used for emergency stopping, lateral support to the pavement and pedestrians. 3. **Camber (cross fall):** the transverse slope of the carriageway (2-3% for paved roads) to drain off water. 4. **Kerbs:** raised edges between the carriageway and the footpath/median (urban roads and bridges). 5. **Median (central reserve):** on divided highways, a strip separating opposite directions of traffic, with a width of 1.2 m (minimum) to 5 m (desirable). 6. **Side drains:** open drains beside the road, usually trapezoidal or triangular. 7. **Side slopes:** slopes of the embankment (e.g. 2H:1V, i.e. 2 horizontal to 1 vertical) or cutting. 8. **Formation (roadway) width:** carriageway + shoulders (+ median on divided roads); the top width of the embankment or the bottom width of the cutting, excluding the side drains. 9. **Right of way (ROW):** the total width of land acquired for the road, with allowance for widening, utilities and services (NRS 2070: 50 m for National Highways and 30 m for Feeder Roads). 10. **Footpath, cycle track and service road:** in urban stretches. 11. **Roadside planting, guard rails, signs** and **boundary stones**. 12. **Building line and control line:** the lines beyond which construction is restricted. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What are shoulders mainly used for? A. Carrying the main traffic lanes B. Draining water from the crown C. Emergency stopping, lateral support to the pavement and pedestrians D. Separating opposite traffic streams Answer: C. Shoulders on both sides of the carriageway give lateral support and space for emergency stops and pedestrians. (Key point: Carriageway and shoulders) 2. What is the purpose of camber (cross fall)? A. To counteract centrifugal force B. To drain rainwater off the carriageway C. To separate pedestrians from vehicles D. To increase the formation width Answer: B. Camber is the transverse slope of the carriageway that drains water to the sides. (Key point: Camber) 3. How do formation width and right of way differ? A. They are the same width B. Formation width is the total land acquired; ROW is carriageway plus shoulders C. Formation width is the width at subgrade level (carriageway + shoulders etc.); ROW is the total land acquired D. Formation width includes building lines; ROW does not Answer: C. Formation width is the roadway width at subgrade level, while the right of way is the whole land strip acquired including future widening and utilities. (Key point: Formation width vs right of way) 4. Where is a median (central reserve) provided? A. On divided highways between opposite directions of traffic B. Between the shoulder and the side drain C. Only on single-lane hill roads D. At the edge of embankments Answer: A. A median is a strip separating opposite traffic directions on divided highways. 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