Why in news?

In a move to ensure uniformity and consistency in the construction of high-speed corridors — also known as access-controlled national highways or expressways — the National Highways Authority of India (NHAI) has issued detailed guidelines covering design, standards and specifications for such projects.

Until now, consultants prepared Detailed Project Reports (DPRs) for these corridors based on varying standards and specifications, leading to inconsistency across projects.

What’s in Today’s Article?

• The Bigger Picture: Vision 2047
• How Traffic Will Be Assessed?
• Lane Configuration Norms
• Access Control and Design Standards
• Signage and Road Marking Standards
• Barrier-Less Tolling and Corridor Protection
• Green and Sustainable Design Elements

The Bigger Picture: Vision 2047

• The move gains significance because India targets 50,000 km of high-speed corridors by 2036–37 under Vision 2047.
• These corridors are special sections of national highways providing uninterrupted, end-to-end travel.
• The total length of high-speed corridors stood at just 3,052 km as of December 2025 — showing the scale of expansion planned ahead.

How Traffic Will Be Assessed

• NHAI has mandated a more rigorous approach to traffic assessment for these projects.
  • Assessment must include existing, generated, induced, and diverted traffic, based on proper traffic modelling.
  • Freight growth rate must be analysed considering economic development.
  • Traffic data must be validated from secondary sources such as toll transactions.
  • For freight traffic and determining the Vehicle Damage Factor (VDF), data from GST portals, mining departments and other sources must be cross-validated.

Lane Configuration Norms

• The guidelines set clear, traffic-based thresholds for how many lanes a corridor should have:
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• This tiered approach ensures highways are built to match actual and projected traffic volumes, rather than a one-size-fits-all design.

Access Control and Design Standards

• The core principle behind access-controlled highways is protecting the speed of long-distance through traffic from local interference.
  • Access must be planned so that through traffic can move at the speed set by the main highway flow — not slowed by local, access, or cross traffic.
  • There shall be no at-grade intersection of any road with the project highway.
  • Access to the highway must be through properly designed ramps at planned locations.
• Underpass height: In areas with frequent operation of heavy agricultural machinery — harvesters and laden tractors — underpass height may be set at 4.50 metres, accommodating farm vehicle movement.
• Service roads: These must be provided in built-up and urban sections on both sides, along with a drain-cum-footpath, ensuring local connectivity and pedestrian safety alongside the high-speed corridor.

Signage and Road Marking Standards

• NHAI has also standardised signage placement for driver clarity and safety:
  • Full overhead gantries (carrying direction signs) shall be placed 5 km and 2 km ahead of an exit.
  • Cantilever gantries (carrying advance direction signs) shall be placed 1 km and 500 metres before the exit.
  • Lane and other markings must be 150 mm wide.
  • Edge-lane markings must be 200 mm wide.

Barrier-Less Tolling and Corridor Protection

• NHAI is shifting towards a Multi-Lane Free Flow (MLFF) system — essentially a barrier-less tolling mechanism that allows vehicles to pass through toll points without stopping.
• The new guidelines require provisions for this system to be incorporated into corridor layout design from the outset.
• Preventing encroachment: To stop unauthorised access and encroachment on high-speed corridors, a 1-metre-high RCC (Reinforced Cement Concrete) boundary wall must be constructed along the extreme outer edge of the Right of Way (ROW).
  • ROW refers to the total width of land legally acquired or owned by the government or road authority for construction, operation, maintenance, and future highway expansion.

Green and Sustainable Design Elements

• The guidelines also embed environmental considerations into corridor planning:
  • Drip irrigation will be provided in the median for watering plants.
  • Tree plantation will be made an integral part of project design at the DPR stage itself — not an afterthought.

Conclusion

NHAI's new rules replace guesswork with a uniform rulebook — from lane width to tree plantation. As India races toward 50,000 km of high-speed corridors, consistency in design will matter as much as the pace of construction. Standardisation today prevents costly retrofits tomorrow.