However, depending on the type of trip, you might use:
* A series of trips: A circuit of trips
* Trips taken together: A tour of trips
* Trips with a specific purpose: A mission of trips
* Trips taken for pleasure: A jaunt of trips
You could also use descriptive phrases like:
* A collection of trips
* A string of trips
* A set of trips
Ultimately, the best way to describe a group of trips depends on the context and what you want to emphasize.