Trains would still work well. Have a train track that runs through gateways and it's a quick and easy way to transport large groups of people.

You should read Peter F. Hamilton's Commonwealth Saga. It's a science fiction story where humanity has colonized multiple planets, and there is an entire system of trains set up that make interplanetary journeys through wormholes. The Seanchan could have done something similar, with terminals that connect via gateways to other cities.