There are additional details about the Location Sharing Options (HERE)
In the Mileage Policies there is the option to Share Locations
You can opt-in to sharing locations by checking the box next to the Sharing Locations Among users under the Address Book Section
Sharing among users will create locations for all users. If there are a high number of locations it may hinder site performance if one or more of the additional filters are not selected.
You have 3 additional options to select:
Only Share Imported : Only sharing locations imported to the account, the owner is the admin that imported them. If the owner modifies the location all records using that location will change. Good for allowing the control to be with the admin and the ability to update location details like phone numbers or default activities.
Only Share Named Locations : This will share any locations between users that have been named. These will assume that the location is the same and will be updated by the owner
Only Share Locations that have a default "Business" activity assigned : This will limit the shared locations to only Locations with the default activity set to Business.
If you find there are many locations duplicated while configuring these settings you can use the Delete Unused Locations tool that will remove any locations that have not been used in a Trip. Go to Mileage > Locations > Delete > Delete Unused. ( Confirm the Delete). Allow time to process depending on how many locations there are.