4 lanes, 6 lanes, 60m or 70m wide? How NHAI will decide the size of your next highway

India’s upcoming high-speed national highways will no longer follow a one-size-fits-all design.

Earlier this week, the National Highways Authority of India (NHAI) said the lane configuration of high-speed national highways will be standardised based on detailed traffic assessments to facilitate seamless movement. And accordingly, it has set a new set of guidelines.

NHAI said in a statement that the key focus of the guidelines is on incorporation of additional safety measures appropriate with high-speed traffic conditions on corridors. Special provisions have been prescribed for advance notification of exits and entries, enabling National Highway users to anticipate and safely navigate upcoming access and egress points.

The guidelines will apply to the upcoming 4-lane and 6-lane Greenfield and Brownfield access-controlled National Highways.

How will NHAI decide the number of lanes?

The key factor will be traffic flow.

• For corridors expected to carry up to 15,000 vehicles, NHAI has prescribed a four-lane highway with four-lane structures, with the corridor having a 60-metre width.
• For roads with traffic between 15,000 and 25,000 vehicles, the highway will have a four-lane configuration but six-lane structures, with the overall width increasing to 70 metres.
• For corridors carrying between 25,000 and 40,000 vehicles, NHAI has prescribed a six-lane highway with six-lane structures, also with a 70-metre width.
• The traffic assessment will therefore determine not just the number of lanes but also the broader design requirements of the highway.

Why has NHAI introduced the new rules?

Until now, there were no separate standards specifically governing the planning and design of access-controlled high-speed National Highways, apart from expressways.

NHAI said variations had been observed in the standards used while preparing Detailed Project Reports (DPRs) for such corridors. The new guidelines seek to address this by establishing a common framework of technical and safety provisions.

The rules also introduce additional safety measures suited to high-speed traffic. For instance, exits and entries will have to be notified in advance so that motorists have more time to anticipate and safely navigate access and egress points.

More interchanges, tighter access control

NHAI also plans to provide ramp-based interchanges where these highways cross expressways, National Highways, State Highways and important arterial roads that generate substantial traffic.

Interchanges will also connect highways to major traffic-generating destinations such as ports, airports, Multi-Modal Logistics Parks (MMLPs), industrial areas and major tourist destinations.

To prevent unauthorised access and the entry of stray cattle, the guidelines prescribe a 1-metre-high boundary wall along the outer edge of high-speed corridors.

The new framework is part of the government’s longer-term plan to develop 50,000 km of access-controlled High-Speed Corridors under Viksit Bharat 2047, with the stated aim of improving connectivity and reducing logistics costs.