E4 is the second Shinkansen that has a completely bi-level design, operating by -the East Japan Railway Company on Tōhoku and Jōetsu Shinkansen. It has a maxium speed of 240km/h, and can carry more than 800 passengers at a time. The train was designed to have the ability to couple with another train, giving a more flexibility use of the train arrangement
Why do you think engineers need to design a new bi-level Shinkansen?
https://www.youtube.com/watch?v=FUqAZ5kGmew
Jasper's Blog on Trains 