Why is India's Konkan coast highway called NH66, not NH17?

If you have ever planned a Mumbai to Goa or Goa to Kochi drive off an old map or an older Team-BHP thread, you have probably run into two different numbers for what is the same road: NH17 and NH66. Both are correct. They just belong to different years.

Why the number changed

NH66 is the new name for the old NH17, the Konkan and Malabar coastal highway that most Western Ghats road trippers grow up calling the Bombay-Goa highway. On 28 April 2010 the Ministry of Road Transport and Highways notified a rationalised numbering scheme for the entire national highway network. Under it, the old NH17 was merged with a stretch of the old NH47 and renumbered as NH66.

Today NH66 runs 1,640 km from Panvel, just east of Mumbai, to Kanyakumari at the southern tip of Tamil Nadu, staying close to the coast and parallel to the Western Ghats through Maharashtra, Goa, Karnataka, Kerala and Tamil Nadu.

How the new numbers were decided

The 2010 scheme replaced India's older, fairly random highway numbering with a directional logic. Highways running broadly north to south got even numbers, highways running broadly east to west got odd numbers, and the numbers increase from east to west and north to south across the country. That is why NH44, the Srinagar to Kanyakumari highway, is the longest number on the grid, and why a coastal road running north to south like the old NH17 picked up an even number, 66, instead of keeping an odd one.

Why riders still see NH17 on old boards

The rollout of new signboards took years and, on some stretches, is still catching up. A widely cited account of the renumbering from 2013 found official highway documents and milestone stones showing the old number years after the new one had been notified, so a driver following an old guidebook reference to NH17 could suddenly run into a signboard reading NH66 with no explanation in between. That mismatch is why riders' forums and GPS apps often carry both numbers for the same stretch even now, and why older Team-BHP travelogues of Konkan monsoon drives still refer to the road as NH17 out of habit.

What this means for your road trip

For a Western Ghats or Konkan coast trip planned today, treat NH66 as the number to search for tolls, diversions and NHAI advisories, since that is what current official notices use. But do not be surprised if a local hotel desk, an old milestone or a fellow rider still calls it NH17. Large sections are also mid-upgrade. A roughly 643 km stretch through Kerala was being widened into a six-lane, signal-free corridor with service roads, with about 450 km finished and the rest targeted for around January 2026, according to a report that also flagged quality concerns on a few elevated sections after partial collapses. That is worth factoring into any monsoon season plan, since widening work and heavy rain on the same stretch rarely go together well.

Sources

• 2010 renumbering of national highways in India, Wikipedia
• National Highway 66 (India), Wikipedia
• The National Highways renumbering confusion, Trayaan
• Kerala's NH 66 upgrade nears completion, Maritime Gateway