The Tribhuvan Highway: the First Road into the Kathmandu Valley

The Tribhuvan Highway, in Nepali the Tribhuvan Rajpath, is the first motorable road ever built into the Kathmandu Valley and the oldest highway in Nepal. It runs from Kathmandu south to Birgunj on the Indian border opposite Raxaul, and it was completed in 1956, with construction work running through the first half of the decade. Published figures for its length vary between roughly 158 and 189 km depending on where the count starts and stops.

It was built with Indian government assistance, by Indian engineers working with Nepali labour, in the years immediately after the fall of the Rana regime in 1951, when the new political settlement in Kathmandu had an urgent interest in connecting the capital to the outside world. It is named for King Tribhuvan, who died in 1955, a year before it opened.

The moment that closed the old world is easy to date. When the road was finished, a jeep drove from Birgunj to Kathmandu. It was the first time a motor vehicle had reached the capital on its own wheels. Everything about Thankot before that year, and a great deal about Thankot since, hinges on that single trip.

The engineers had very little choice, and the reason is the same reason there had been a customs post here for centuries.

The Kathmandu Valley is a bowl with a high rim. On the western side, the saddle at Nagdhunga above Thankot is the lowest and least difficult crossing, and the ground below it on the valley side descends to Thankot at about 1,301 m on open, flat land with water. Any road coming from the south and west, following the grain of the hills through Chitlang or Naubise, arrives at that saddle. The alternative alignments are higher, steeper and longer.

So the highway of 1956 came in exactly where the porters had come in, where the salt had come in, where the Gorkhali blockade had sat, and where the trail from Chitlang had always come down. Modern road engineering did not discover a new way into the valley. It paved the old one.

This is worth stating because it explains why Thankot, a town of moderate size, keeps appearing at the centre of national events. It is not that anything special happens here. It is that everything has to pass through here.

The route the builders took is why the Rajpath has the reputation it has. Instead of following the river valleys, it climbs directly over the Mahabharat range, reaching about 2,504 m at Sim Bhanjyang above Daman before descending through Palung and Tistung toward Naubise and then over Nagdhunga into the valley.

The result is one of the most severely engineered mountain roads in South Asia: a continuous sequence of hairpin bends with very little straight road between them, cut into slopes that in places are close to sheer. Drivers who know it will tell you the bend count, and the numbers they give never agree. The engineering ambition of it, achieved in the early 1950s in a country that had no road network at all to build from, is genuinely remarkable.

Daman, near the high point, became known as one of the great Himalayan viewpoints in Nepal, with a panorama running along the range on a clear winter morning. It exists as a destination only because the road went that way.

The choice of alignment has been second-guessed ever since, and the criticism is fair: the route is slow, exposed and expensive to keep open. It was also buildable in the time and with the resources available, which the alternatives were not.

Four things changed at once, and the town has been shaped by all of them since.

The porter trade ended. The extraordinary business of carrying cars over the hills, described in our chronicle on the Thankot car porters, stopped within a year. So, gradually, did much of the general portering on the southern route. A whole category of hill livelihood disappeared.

Buses started. Nepal's first bus services began in the same period. For the first time a person in the middle hills could reach Kathmandu in a day, sitting down, for a fare. The social consequences of that are larger than the freight consequences.

Thankot became a road town. The old bazaar had been built to serve people walking in. Within a generation the town was serving trucks: workshops, tyre repair, tea shops, transport offices, and the beginning of the ribbon development along the highway that now runs most of the way to Kalanki.

The valley stopped being closed. Cement, steel, fuel and manufactured goods could now enter in bulk, and Kathmandu's twentieth century construction boom follows directly. The concrete that rebuilt half the rim towns after 2015 came in on this corridor.

The Rajpath's period as the country's main artery was shorter than you would expect. The Prithvi Highway, running west from Naubise to Pokhara, and later improved routes south through Mugling and Narayangadh, gave traffic a longer but far gentler alternative to the Sim Bhanjyang crossing. Freight and buses moved onto them.

What that did to the Rajpath was demote it, from national artery to scenic secondary road with a devoted following among motorcyclists, cyclists and people going to Daman. What it did to Thankot was the opposite. All the traffic on the newer western routes still has to come over Nagdhunga to enter the valley, so Thankot lost none of its volume and gained a great deal.

The consequence is the defining daily fact of the town: congestion at Nagdhunga. The climb out of the valley is steep enough that heavy trucks crawl it, and a single breakdown or landslide on the saddle backs traffic up for hours and sometimes closes the western entrance to the capital entirely.

The answer to that congestion, seventy years after the road opened, is a tunnel, and it is now finished.

The Nagdhunga to Sisnekhola tunnel is 2.68 km long and is Nepal's first road tunnel. It was financed by a Japanese ODA loan through JICA of around 22.3 billion yen. The construction contract was signed in November 2019 with completion originally scheduled for 2023, and the work ran long because of the pandemic, contractor delays and local disruption. The final breakthrough came in April 2024 and the tunnel was inaugurated in late July 2026, after roughly eighty months on site.

What it does is bypass the worst of the climb, cutting the time to cross the Nagdhunga section to a fraction of what the surface road takes and removing the heavy vehicles that were the cause of the queue.

For Thankot, this is the largest change to the corridor since 1956, and it is genuinely two-sided. The town gets its air and its road back. It also loses some of the passing trade that comes from being the place where everybody has to stop, which is what the roadside economy has run on for seventy years. Which way that settles will be visible over the next few years, and it is worth watching, because the same question has been asked of every bypassed town in the world.

Thankot marks the road's arrival with the Tribhuvan Memorial Park, laid out on the highway side of the town in memory of the king the highway is named for. It is a modest park, and for a visitor its interest is mainly in the placement: it stands at the point where the first road into the valley came down off the rim.

To see the highway itself properly, drive or ride the Rajpath south from Naubise to Daman, ideally staying overnight so you get the range at dawn. Allow far more time than the distance suggests. The road is the attraction and the average speed is low.

For the corridor at Thankot, the best vantage is from above. The Chandragiri cable car lifts you clear of it in nine minutes, and from the ridge the whole arrangement is legible at once: the saddle, the tunnel portals, the ribbon of the highway, the town at the foot of it and the valley behind. Every chronicle on this site is visible from that one spot.