CurrentRoute() can only be used in a Match record action - to get the traveling distance and time between the action's base record and the current match candidate (when used in a Match record action's Rating formula) or the matched record (when used in Match record action's Match actions).
The function works exactly like the Route() function with the only exception that it always builds the route from the base record's location to the matching record, so it doesn't accept coordinates in its input.
If you need to get the distance or time from the matching record's location to the base record's location, use the Route() function to pass the coordinates explicitly.
How to use
params- see its description in Route() function.
See Output of the Route() function.
-CurrentRoute().distancein the Match record's Rating formula (with the minus sign at the start!) to find the closest record to the base location by the driving distance.