Do you link them physically, do you have enough braking distances, or do you, as musk suggests, run pods that are separate close enough that in case of a disaster all pods will crash?
The issue is the required gap to slow down from those speeds.
You might want to take a look at the train crash in Emden at the Transrapid facility.
A maglev train crashed into a maintenance vehicle at a speed of 500km/h because it takes too long to slow down.
The required gaps to operate a maglev system efficiently would end up with one capsule every 10 seconds - which means it can carry less passengers than a lane of highway.
The only way to get more capacity is by running actual trains.
