Yes, for Google Maps you can share your position (Location sharing) with others (and they with you). I assume a Google Account is needed for both parties. This can be turned on and off when needed. You also get general email reminders that you are still sharing your location information.
In the Google Maps application you can see the persons position, based on their gps signal and are somehow connected to the internet.
I found this to be useful where a visitor regularly wanders around the city during the day, to eventually meet in the late afternoon.
Depending in the gps signal, you can the see if the person is on their way back and get a general idea when they will arrive.
Can one view more than one tracked car at once on Google maps?
You are not locating a car, but a person (or more precisely a Google Account that is logged in to a device) that must be in each car. No mention of a maximum amount of 'friends and family' in their text. So assume that more than one is allowed. In the maps application it is shown as a icon with the name on the map.
When moving on a Bus, then the position will 'hop' every few minutes from one position to another. One should look for any refresh setting that may be possible.