When the Vehicle group is no longer in use and you would like to remove them from the mileage. Here are the steps.
Go to Admin > Select Mileage
Select the existing mileage rate where a vehicle group is associated with.
For Example: Your company is no longer using Motorcycles Vehicle group.
3. In the Vehicle Group field, choose 'please select'
4. Click Save
Note: After saving the changes, the vehicle group is no longer available for mileage.