If you wish to merge trips that you've taken, for example during a road trip, this is entirely possible.
From the home screen of your application:
- Click on "View All" in blue within the "Trips" section (below the mini-map).
- Once you're on the list of your trips, click on "Edit" (in blue at the top right of the screen).
- Simply select the relevant trips, then click on the blue merge arrow at the top right, and choose "Merge."