Air resistance is the biggest obstacle to achieving high speeds. My method is based on the fact that the wagon is in the tailwind. The air is transported as fast as the carriage travels. The carriage travels in a rectangular channel. (It can be round but then you get less load space.) Suppose that its gable is 1 m2. The wagon rests on a low friction material. Required force to move= 3 Newton or 3 Pa.

What demands energy is the transportation of air. In one channel there is a pressing fan behind the trolley and in front of a suction. The pressurized fan takes air from a channel running parallel to the aforementioned. Black figure shows carriage. Red arrow air direction and blue figure fan

The channels can be located next to or above each other. They can be built on pylons or buried. The requirement, however, is the same as for all high-speed vehicles - the roads must be as flat and straight as possibly.

Energy will be used to move the air. This need increases with speed - analogous to all vehicles.

Assume the distance 600 km which takes approx. 1 hour gives 5.58 MWh (equivalent to 2 wind turbines - if it blows). The figure shows that the fans are connected in series. Series-mounted fans increase the pressure to double but do not affect the flow - in principle. The rule of thumb states that the power requirement is 1.5 during serial operation. It is only the first fan to accelerate the air and the other only increases the pressure. Here, however, both fans are serially connected to each other.
What about two series-connected fans with feedback flow?
Nobody knows.
No one has asked that question.
The operating case is unique!
When full speed has been reached, the air constitutes the "swing mass". If the distance is 600 km there are 150 tonnes. The motion energy is; m*v2/2. 150,000 * 1672/2 = 2.091675 GWs.

Issues
How much is the energy demand reduced for feedback fans that are connected in series?
How much is the friction in the channels? How much can be done to reduce it?
Benefits of the system
No electrical connection or other infrastructure needs to be pulled into the channels and the carriages need no control.
Since no large pressures occur, the tires' strengths or ducts need not be dimensioned for other than normal conditions.
The channels do not have to be hermetically sealed.
The thermal expansion of the channels (cf. sun curves) can be solved easily.
Installation in the ducts makes the system insensitive to weather and wind. No need for snow raising or worries with falling electrical wires.
Maintenance needs can be assumed to be negligible.
Suitable to build on pylons with the benefits this brings.