Picture a network of one-way wormholes of one-way wormholes that allow nigh-instantaneous travel across thousands of miles, possibly even to other worlds. Now picture a monorail that travels through all of them. A simple train trip could take someone to other cities or other worlds in mere minutes. It would take longer to load and unload the train than it would to travel across galaxies.
Still with me? Now, what if the train was torus shaped. The locomotion would be provided be each car and instead of functioning like a train, it would be more like an enormous turnstyle. It wouldn't have to be all that large, either. Just the length between each wormhole at each stop. Let's say there are twelve stops on the route and twelve cars on the train. One car would always be at each stop. Every fifteen minutes, the train changes position by one car.
What's that, you ask? What's to prevent someone from getting one at one stop, walking to the different cars, and getting off at a different stop without the train actually moving? They check your ticket at every door. Since I concocted the Megarail (patent-pending) for a humorous SF mystery set in a pseudo-Edwardian period, I think the ticket-checker having sole authority on the train works rather well.