If a salesperson or multiple salespeople in your business are responsible for specific customer accounts, you can assign them to the account record so only they can access the account and the associated trips.
Access the account or lead record you want to associate sales reps to
Click "Add New" in the Sales Reps area of the record
Select the sales rep you want to add from the drop down and click "Add"
Note: A user with a manager role (i.e. Operations Manager, Finance Manager, Sales Manager) does have access to the accounts and trips with assigned sales reps.