Road cross-section

A road cross-section is the view across the road at right angles to its centre line. It shows every element that the road user, drainage and maintenance need: carriageway lanes, shoulders, median, kerbs, footpaths, cycle tracks, side drains, embankment or cutting side slopes and the right of way boundary. Designing it well balances capacity, safety, drainage and land take.

The carriageway is set by the number and width of lanes, around 3.5 m each on major highways in India and narrower on low-volume roads. Shoulders give space for stopped vehicles and lateral support to the pavement; paved shoulders also carry slow traffic. A median separates opposing flows on divided roads, reducing head-on crashes and glare, and may hold crash barriers, landscaping or future lanes. Footpaths and cycle tracks, protected by kerbs or verges, are essential in urban sections. The formation width is the total width of the earthwork top on which all of this sits.

Side slopes of embankments and cuttings are chosen for stability and safety, with flatter slopes on high fills and in weak soils, and with protection by turfing or stone pitching against erosion. Camber or crossfall drains water off the surface into side drains. Right of way is the land acquired, wide enough for present needs and planned widening, utilities and service roads. Typical cross-sections are prepared for each category: expressways, national highways, state highways, district and village roads, and urban streets.