Journey starts and Driver gets to a destination along the route, exits the vehicle and one of the other passengers then drives. Therefore Different points along the route would be different driver. (That is where the importance of the whereabouts comes in) and then Different drivers different days on the same journey.
I'm frankly trying to get my head around this multiple driver scenario as described by the OP. If I read it correctly, driver A drives to first destination, gets out and is replaced by passenger B, who then drives to a different destination, gets out and is replaced by passenger C, who then drives... etc.
As someone who has been involved with Six Sigma principles and Lean manufacturing for many years, this gives me a twitchy eye and an itchy stabbing hand.
Why doesn't passenger D (for ex.) drive to the last destination, dropping people off along the way. Why the need for multiple drivers? Unless we are talking absolute miles and maximum driving hours. It makes no sense and to be honest if I was on the bench, a story I would be mildly sceptical of.