This is one of three options to search for the nearest vehicles from any given location. Look here to see alternative ways of achieving the same results.
You have two ways of locating the nearest vehicles from a Place or from another vehicle's current position.
Left-click on the Place or Vehicle to open its infobox:
Then, choose the Find nearest vehicles action, from the Hamburger menu at the top:
Right-click on the Place or Vehicle to open its infobox's actions drop down menu:
From there, choose Find nearest vehicles.
In either case, Frotcom will show you a list with the nearest vehicles from the Place or Vehicle you have selected.