Japan is resuming trial runs for the world's fastest magnetic-levitation train that will complement the Shinkansen bullet-train network when ready in 2027.

Central Japan Railway plans to begin work on the 5.1 trillion yen ($51 billion) maglev line between Tokyo and Nagoya as early as April. Trial runs resumed on Thursday after the company spent five years building a 24-kilometre extension of a test track. The trains can run at speeds of up to 500 kilometres per hour.

Faster than a speeding bullet train: Japan is testing a maglev (magnetic levitation) train capable of reach speeds up to 581 km/h. Credit:Getty Images

The maglevs will whisk passengers to Nagoya, a city of 2.3 million people, from Tokyo in as little as 40 minutes for the 286-kilometre journey, from as short as 95 minutes now, according to JR Central. Faced with the challenge of tunneling under Tokyo's skyscrapers and Japanese Alps, the project is unlikely to be completed on time even as Japan's population is projected to shrink.

"I think it's going to be finished very, very late," said Edwin Merner, president of Atlantis Investment Research in Tokyo, which manages about $3 billion in assets. "If the population projections are correct, then the use of the bullet train will go down."