Check out this wild concept video from China for a nonstop train designed around detachable passenger pods:

Basically, passengers would “preboard” onto a top-level compartment that would, essentially, be a movable station. I’m thinking access in and out would have to be shut down X number of minutes prior to the shove-off, to avoid having people get caught — to tragic effect. Then, once that top-level compartment was on the move, passengers would be hustled down below to the “main train” for the duration of their ride, and have to ascend again when they’re nearing their stop. Again, there would have to be shut-downs to access to avoid disasters, so it’s a lot of coordinated people-herding, but it could be done.

Here’s the benefit:

Airplanes, cars, train locomotives and other vehicles waste the most energy when going into motion from a dead stop. Thus ideally, the most efficient transport is one that could move perpetually, never stopping to refuel, reload or pick up passengers.

Not only would it save energy, but keeping the train in constant motion means shorter travel time, especially if you’re passing through several stops before your final destination. So there’s a tangible benefit for the riders as well.