Inside North Korea leader Kim Jong-un's train journey to Vietnam

It will take two-and-a-half days for Mr Kim to travel from Pyongyang to Hanoi, but he will be doing so in comfort

Armour-clad carriages, tinted windows and a maximum speed of 60 kilometres per hour – they're the unique features of the leader of North Korea's preferred mode of transport, his train.

The Supreme Leader of North Korea, Kim Jong-un set off for Vietnam for his second summit with US President Donald Trump on Sunday, leaving three days before the start of the meeting due to the train's unusually slow top speed – reportedly on account of the heavy bulletproof armour.

Mr Kim received a red-carpet send-off in Pyongyang as he waved from the carriage door – painted a dull green, with a distinctive yellow stripe – while holding a cigarette.

His route will take him across North Korea's northern border, around the Bohai Sea, along China's eastern coastline and into Vietnam on its northernmost edge.

Three generations of North Korean leaders have travelled on these trains, piquing the interest of avid watchers of the insular country and speculation about conditions on board.

Although the details of the train are highly secretive, reports over the years paint a picture of a palace on the move – a high-security fortress and all of the home comforts a supreme leader could reasonably desire.

Those who have travelled on the train report an extensive menu including fresh lobster, fine wines flown from Paris and "lady conductors".

But it is not all about lavish dining – the carriages are reportedly kitted out with flat-screen televisions, state-of-the-art communications equipment, plush conference lounges and Mr Kim's MacBook.

A convoy of three trains operate each time North Korea's leader travels, The New York Times reported last year: an advanced security train, the leader's train and another carrying necessary supplies – bodyguards, food, equipment.

It is thought that there are some 90 carriages for the North Korea leader to choose from, all highly reinforced to quell the fears of the notoriously paranoid Mr Kim.

Trains have taken North Korea's leaders across Asia and beyond. The longest journey was undertaken by Mr Kim's father, who travelled across the Soviet Union by train.

The incumbent leader, however, has been marginally less expeditionary and has only travelled to Beijing by train in March last year.

A worker is seen on a tree next to a banner showing North Korean and US flags ahead of the summit between Donald Trump and Kim Jong-un in Hanoi. Reuters

Vietnamese soldiers stand guard outside of Dong Dang railway station. Getty Images

Vietnamese police leave their headquarters to patrol ahead of the upcoming North Korea-US summit. Reuters

An armoured police truck leaves their headquarters to patrol. Reuters

A man fixes an electric line next to pictures of Vietnam, US and North Korean national flags. AFP

Vietnamese police officers stand guard outside the Melia Hotel where a number of North Korean delegates are staying. Getty Images

Shop assistants react to the camera after having their photographs taken by a friend next to T-shirts celebrating the forthcoming North Korea-USA summit. Getty Images

The Marriott hotel, where Donald Trump is expected to stay during his visit to Hanoi. Getty Images

Vietnamese police arrive at the Dong Dang railway station. AFP

Vietnamese soldiers patrol around the Dong Dang railway station. AFP

While Mr Kim will be travelling to Vietnam by train, last June during his first meeting with Mr Trump, the leader borrowed an Air China-branded plane from his Chinese neighbours.

Mr Kim's private plane is a 38-year-old Soviet Ilyushin Il-62. Unreliable and with spare parts no longer in production, aviation and North Korea experts speculated it was ditched for the summit to avoid the embarrassment of being stuck or delayed by a minor malfunction.

It is not known why North Korea's leader did not fly to his second summit with the US president, but with a long journey ahead, he might soon invest in some wings similar to Air Force One.