The OSRM platform API is a free alternative to do distance calculation between the two points. However, it is a service that has the support of employees, which can lead to some problems.

For example, a person may corrupt the database by misleading the account. Very remote areas do not have an expressive database.

Among the advantages is the fact of being a service completely free and with results in some areas very close to the real one. I still think it is up to the scientific community to do more research to validate the results of the API.