The world’s longest highway is in Australia. 

It is 14,500 kilometers long and goes nowhere in particular because it is a loop. Highway 1 circles the entire Australian continent, connecting every mainland state and territory capital along a coastal route with no start and no end. 

This visualization ranks the top 15 longest highways on Earth. It is based on data from the national transport authority, the United Nations transport network designations, and published road statistics, gathered by Wikipedia. 

TL;DR

• Australia’s Highway 1 is the longest road at 14,500km, but it is a loop that circles the entire continent with no fixed start or end point

Highway 1 leads at 14,500 kilometers, circling Australia’s entire mainland coastline through every state and territory capital. 

Asian Highway 2 is 13,177 kilometers long, running from Denpasar in Bali, Indonesia, to Khosravi in Iran, crossing 13 countries, the Indian subcontinent, and Central Asia before reaching a terminus at a border currently complicated by international sanctions. 

The Pan-American Highway’s North American segment comes third at 11,500 kilometers, from Prudhoe Bay in Alaska to Yaviza in Panama.

Russia’s Trans-Siberian Highway places fourth at 11,000 kilometers, connecting St. Petersburg to Vladivostok across the full width of the country. 

Something about the Pan-American Highway

The Pan-American Highway is supposed to run continuously from Alaska to the southern tip of South America.

That is, a single route connecting the entire Western Hemisphere by road. 

It does not, because of 96 kilometers of jungle.

The Darién Gap, on the Panama-Colombia border, has never been paved. It is a stretch of roadless rainforest and swamp that the two countries have declined to bridge since the highway concept was first proposed in the 1920s. 

Panama and Colombia have both cited the Darién National Park (a UNESCO World Heritage site) as the primary justification. 

The gap has also served as a natural barrier against the spread of foot-and-mouth disease from South American livestock into Central and North America.

If complete, a continuous Pan-American Highway would run approximately 21,100 kilometers, easily surpassing Australia’s loop as the longest road on earth.

China Highways 

National Highway 219 runs 10,000km from Xinjiang in the northwest to Guangxi in the south, connecting remote border territory to the Chinese economic heartland. 

National Highway 331 connects Dandong (on the North Korean border in Liaoning) to Altay in Xinjiang, spanning the entire width of China’s northern tier. 

 The United States, which began building its interstate system in 1956 and has approximately 77,960 kilometers of interstate highways, does not appear once.

Its longest individual interstate (I-90 from Boston to Seattle at approximately 4,860 kilometers) falls below the top 15.

ELI5

A list of the longest highways in the world shows Australia’s Highway 1 is the biggest at 14,500km, but it’s just a big circle around the whole country. America, despite being famous for highways, has none long enough to qualify in the top 15. The Pan-American Highway, which is meant to run from Alaska all the way to the bottom of South America, has a 96km jungle gap that has never been filled in, so it is treated as two separate roads.

Source: 

Wikipedia (drawn from national transport authority data, United Nations transport network designations, and published road statistics).