What are the drawbacks of bullet trains?

Alfonso Llanes, studied at Florida International University

Answered just now

There several high-speed design proposals for mass transit in addition to the existing bullet train. One of the biggest problems with anything moving is the physics of friction on a surface or a medium such as air, water or a vacuum. For this reason engineering and construction costs are exponentially high and related to an increase on the speed of any surface vehicle.

A design such as the Hyperloop proposes to do away with traditional wheels by using air bearings and pods instead. This allows the pod to float on air. The design is similar to the maglev, in which the electromagnetic levitation of the train avoids friction unlike a traditional train that runs on tracks.

This is how current maglev trains can achieve super speeds, like the 500km/h maglev train in Japan. One Hyperloop design, from Virgin Hyperloop One, uses “passive magnetic levitation”, meaning the magnets are on the trains and work with aluminum track. Current active maglevs need powered tracks with copper coiling, which is very expensive.

Maglev (derived from magnetic levitation) is a public transport technology that uses magnetic levitation to move vehicles without making contact with the ground or an electrical conduit. Maglev ultimate concept is to compete with high speed rail and airlines.

Maglev technology has fewer moving parts, allowing vehicles to move more smoothly, quietly and faster than transport on wheels. A vehicle travels along a guide way equipped with magnets to control “in-flight” stability and create propulsion and lift, thus, eliminating the physical constraints of friction. In the case of conventional high speed trains, there is a lot of wear and tear of wheels on rails and on the electrical pickup which limit higher speeds.

Maglev vehicles hold the speed record for trains. In practice, as with all high speed transport, time for acceleration and deceleration must be included with having fewer stops if higher top speeds are to be effectively utilized. In the case of maglev, acceleration and deceleration are in essence restricted to protect the safety and comfort of the passengers.

Vactrain technology has been proposed as a means to overcome this limitation. Elon Musk has started the building revolution for a new train system. It's based on the very high-speed transit (VHST) system proposed in 1972. The system combines magnetic levitation with moving in a vacuum transit tube. It has evolved from the original ideas of VHST, but it still uses the tubes and pods to move from place to place liken to the tube-pod combination used by banks to send paperwork from office to office only in a larger scale.